Merge branch '0.6.0' into new_transformers

Small collisions

README.md

@@ -165,3 +165,5 @@ If you're interested in taking one of these on, let me know and I will provide m
 If you have any questions or want my assistance, you can email me at erezshin at gmail com.
 
 I'm also available for contract work.
+
+ -- [Erez](https://github.com/erezsh)

docs/reference.md

@@ -1,176 +0,0 @@
-# Lark Reference
-
-## What is Lark?
-
-Lark is a general-purpose parsing library. It's written in Python, and supports two parsing algorithms: Earley (default) and LALR(1).
-
-Lark also supports scanless parsing (with Earley), contextual lexing (with LALR), and regular lexing for both parsers.
-
-Lark is a re-write of my previous parsing library, [PlyPlus](https://github.com/erezsh/plyplus).
-
-## Grammar
-
-Lark accepts its grammars in [EBNF](https://www.wikiwand.com/en/Extended_Backus%E2%80%93Naur_form) form.
-
-The grammar is a list of rules and terminals, each in their own line.
-
-Rules and terminals can be defined on multiple lines when using the *OR* operator ( | ).
-
-Comments start with // and last to the end of the line (C++ style)
-
-Lark begins the parse with the rule 'start', unless specified otherwise in the options.
-
-It might help to think of Rules and Terminals as existing in two separate layers, so that all the terminals are recognized first, and all the rules are recognized afterwards. This is not always how things happen (depending on your choice of parser & lexer), but the concept is relevant in all cases.
-
-### Rules
-
-Each rule is defined in terms of:
-
-    name : list of items to match
-         | another list of items    -> optional_alias
-         | etc.
-
-An alias is a name for the specific rule alternative. It affects tree construction.
-
-An item is a:
-
- - rule
- - terminal
- - (item item ..) - Group items
- - [item item ..] - Maybe. Same as: "(item item ..)?"
- - item? - Zero or one instances of item ("maybe")
- - item\* - Zero or more instances of item
- - item+ - One or more instances of item
-
-
-Example:
-
-    float: "-"? DIGIT* "." DIGIT+ exp
-         | "-"? DIGIT+ exp
-
-    exp: "-"? ("e" | "E") DIGIT+
-
-    DIGIT: /[0-9]/
-
-### Terminals
-
-Terminals are defined just like rules, but cannot contain rules:
-
-    NAME : list of items to match
-
-Example:
-
-    IF: "if"
-    INTEGER : /[0-9]+/
-    DECIMAL: INTEGER "." INTEGER
-    WHITESPACE: (" " | /\t/ )+
-
-## Tree Construction
-
-Lark builds a tree automatically based on the structure of the grammar. Is also accepts some hints.
-
-In general, Lark will place each rule as a branch, and its matches as the children of the branch.
-
-Terminals are always values in the tree, never branches.
-
-In grammar rules, using item+ or item\* will result in a list of items.
-
-Example:
-
-    expr: "(" expr ")"
-        | NAME+
-
-    NAME: /\w+/
-
-    %ignore " "
-
-Lark will parse "(((hello world)))" as:
-
-    expr
-        expr
-            expr
-                "hello"
-                "world"
-
-The brackets do not appear in the tree by design.
-
-Terminals that won't appear in the tree are:
-
- - Unnamed literals (like "keyword" or "+")
- - Terminals whose name starts with an underscore (like \_DIGIT)
-
-Terminals that *will* appear in the tree are:
-
- - Unnamed regular expressions (like /[0-9]/)
- - Named terminals whose name starts with a letter (like DIGIT)
-
-## Shaping the tree
-
-a. Rules whose name begins with an underscore will be inlined into their containing rule.
-
-Example:
-
-    start: "(" _greet ")"
-    _greet: /\w+/ /\w+/
-
-Lark will parse "(hello world)" as:
-
-    start
-        "hello"
-        "world"
-
-
-b. Rules that receive a question mark (?) at the beginning of their definition, will be inlined if they have a single child.
-
-Example:
-
-    start: greet greet
-    ?greet: "(" /\w+/ ")"
-          | /\w+ /\w+/
-
-Lark will parse "hello world (planet)" as:
-
-    start
-        greet
-            "hello"
-            "world"
-        "planet"
-
-c. Rules that begin with an exclamation mark will keep all their terminals (they won't get filtered).
-
-d. Aliases - options in a rule can receive an alias. It will be then used as the branch name for the option.
-
-Example:
-
-    start: greet greet
-    greet: "hello" -> hello
-         | "world"
-
-Lark will parse "hello world" as:
-
-    start
-        hello
-        greet
-
-## Lark Options
-
-When initializing the Lark object, you can provide it with keyword options:
-
-- start - The start symbol (Default: "start")
-- parser - Decides which parser engine to use, "earley" or "lalr". (Default: "earley")
-           Note: "lalr" requires a lexer
-- lexer - Decides whether or not to use a lexer stage
-    - None: Don't use a lexer
-    - "standard": Use a standard lexer
-    - "contextual": Stronger lexer (only works with parser="lalr")
-    - "auto" (default): Choose for me based on grammar and parser
-
-- transformer - Applies the transformer to every parse tree (only allowed with parser="lalr")
-- postlex - Lexer post-processing (Default: None)
-
-To be supported:
-
-- debug
-- cache\_grammar
-- keep\_all\_tokens
-- profile - Measure run-time usage in Lark. Read results from the profiler property (Default: False)

examples/README.md

@@ -10,6 +10,8 @@
 
 ### Advanced
 
+- [error\_reporting\_lalr.py](error_reporting_lalr.py) - A demonstration of example-driven error reporting with the LALR parser
 - [python\_parser.py](python_parser.py) - A fully-working Python 2 & 3 parser (but not production ready yet!)
-- [conf.py](conf.py) - Demonstrates the power of LALR's contextual lexer on a toy configuration language
+- [conf\_lalr.py](conf_lalr.py) - Demonstrates the power of LALR's contextual lexer on a toy configuration language
+- [conf\_earley.py](conf_earley.py) - Demonstrates the power of Earley's dynamic lexer on a toy configuration language
 - [reconstruct\_json.py](reconstruct_json.py) - Demonstrates the experimental text-reconstruction feature

examples/conf_nolex.py → examples/conf_earley.py

@@ -1,16 +1,14 @@
 #
-# This example demonstrates scanless parsing using the dynamic-lexer earley frontend
+# This example demonstrates parsing using the dynamic-lexer earley frontend
 #
 # Using a lexer for configuration files is tricky, because values don't
 # have to be surrounded by delimiters. Using a standard lexer for this just won't work.
 #
 # In this example we use a dynamic lexer and let the Earley parser resolve the ambiguity.
 #
-# Future versions of lark will make it easier to write these kinds of grammars.
-#
 # Another approach is to use the contextual lexer with LALR. It is less powerful than Earley,
 # but it can handle some ambiguity when lexing and it's much faster.
-# See examples/conf.py for an example of that approach.
+# See examples/conf_lalr.py for an example of that approach.
 #
 
 
@@ -19,14 +17,14 @@ from lark import Lark
 parser = Lark(r"""
         start: _NL? section+
         section: "[" NAME "]" _NL item+
-        item: NAME "=" VALUE _NL
-        VALUE: /./*
+        item: NAME "=" VALUE? _NL
+        VALUE: /./+
         %import common.CNAME -> NAME
         %import common.NEWLINE -> _NL
 
         %import common.WS_INLINE
         %ignore WS_INLINE
-    """, lexer='dynamic')
+    """, parser="earley")
 
 def test():
     sample_conf = """
@@ -34,6 +32,7 @@ def test():
 
 a=Hello
 this="that",4
+empty=
 """
 
     r = parser.parse(sample_conf)

examples/conf.py → examples/conf_lalr.py

@@ -1,16 +1,16 @@
 #
 # This example demonstrates the power of the contextual lexer, by parsing a config file.
 #
-# The tokens NAME and VALUE match the same input. A regular lexer would arbitrarily
+# The tokens NAME and VALUE match the same input. A standard lexer would arbitrarily
 # choose one over the other, which would lead to a (confusing) parse error.
-# However, due to the unambiguous structure of the grammar, the LALR(1) algorithm knows
+# However, due to the unambiguous structure of the grammar, Lark's LALR(1) algorithm knows
 # which one of them to expect at each point during the parse.
 # The lexer then only matches the tokens that the parser expects.
 # The result is a correct parse, something that is impossible with a regular lexer.
 #
 # Another approach is to discard a lexer altogether and use the Earley algorithm.
 # It will handle more cases than the contextual lexer, but at the cost of performance.
-# See examples/conf_nolex.py for an example of that approach.
+# See examples/conf_earley.py for an example of that approach.
 #
 
 from lark import Lark
@@ -25,13 +25,14 @@ parser = Lark(r"""
 
         %import common.WS_INLINE
         %ignore WS_INLINE
-    """, parser="lalr", lexer="contextual")
+    """, parser="lalr")
 
 
 sample_conf = """
 [bla]
 a=Hello
 this="that",4
+empty=
 """
 
 print(parser.parse(sample_conf).pretty())

examples/error_reporting_lalr.py

@@ -0,0 +1,81 @@
+#
+# This demonstrates example-driven error reporting with the LALR parser
+#
+
+from lark import Lark, UnexpectedToken
+
+from .json_parser import json_grammar   # Using the grammar from the json_parser example
+
+json_parser = Lark(json_grammar, parser='lalr')
+
+class JsonSyntaxError(SyntaxError):
+    def __str__(self):
+        context, line, column = self.args
+        return '%s at line %s, column %s.\n\n%s' % (self.label, line, column, context)
+
+class JsonMissingValue(JsonSyntaxError):
+    label = 'Missing Value'
+
+class JsonMissingOpening(JsonSyntaxError):
+    label = 'Missing Opening'
+
+class JsonMissingClosing(JsonSyntaxError):
+    label = 'Missing Closing'
+
+class JsonMissingComma(JsonSyntaxError):
+    label = 'Missing Comma'
+
+class JsonTrailingComma(JsonSyntaxError):
+    label = 'Trailing Comma'
+
+
+def parse(json_text):
+    try:
+        j = json_parser.parse(json_text)
+    except UnexpectedToken as ut:
+        exc_class = ut.match_examples(json_parser.parse, {
+            JsonMissingValue: ['{"foo": }'],
+            JsonMissingOpening: ['{"foo": ]}',
+                                 '{"foor": }}'],
+            JsonMissingClosing: ['{"foo": [}',
+                                 '{',
+                                 '{"a": 1',
+                                 '[1'],
+            JsonMissingComma: ['[1 2]',
+                               '[false 1]',
+                               '["b" 1]',
+                               '{"a":true 1:4}',
+                               '{"a":1 1:4}',
+                               '{"a":"b" 1:4}'],
+            JsonTrailingComma: ['[,]',
+                                '[1,]',
+                                '[1,2,]',
+                                '{"foo":1,}',
+                                '{"foo":false,"bar":true,}']
+        })
+        if not exc_class:
+            raise
+        raise exc_class(ut.get_context(json_text), ut.line, ut.column)
+
+
+def test():
+    try:
+        parse('{"key":')
+    except JsonMissingValue:
+        pass
+
+    try:
+        parse('{"key": "value"')
+    except JsonMissingClosing:
+        pass
+
+    try:
+        parse('{"key": ] ')
+    except JsonMissingOpening:
+        pass
+
+
+if __name__ == '__main__':
+    test()
+
+

examples/python_parser.py

@@ -10,7 +10,7 @@ import glob, time
 from lark import Lark
 from lark.indenter import Indenter
 
-__path__ = os.path.dirname(__file__)
+# __path__ = os.path.dirname(__file__)
 
 class PythonIndenter(Indenter):
     NL_type = '_NEWLINE'
@@ -20,18 +20,14 @@ class PythonIndenter(Indenter):
     DEDENT_type = '_DEDENT'
     tab_len = 8
 
+kwargs = dict(rel_to=__file__, postlex=PythonIndenter(), start='file_input')
 
-grammar2_filename = os.path.join(__path__, 'python2.g')
-grammar3_filename = os.path.join(__path__, 'python3.g')
-with open(grammar2_filename) as f:
-    python_parser2 = Lark(f, parser='lalr', postlex=PythonIndenter(), start='file_input')
-with open(grammar3_filename) as f:
-    python_parser3 = Lark(f, parser='lalr', postlex=PythonIndenter(), start='file_input')
+python_parser2 = Lark.open('python2.g', parser='lalr', **kwargs)
+python_parser3 = Lark.open('python3.g',parser='lalr', **kwargs)
+python_parser2_earley = Lark.open('python2.g', parser='earley', lexer='standard', **kwargs)
+print(python_parser3)
 
 
-with open(grammar2_filename) as f:
-    python_parser2_earley = Lark(f, parser='lalr', lexer='standard', postlex=PythonIndenter(), start='file_input')
-
 def _read(fn, *args):
     kwargs = {'encoding': 'iso-8859-1'}
     with open(fn, *args, **kwargs) as f:
@@ -82,6 +78,6 @@ def test_earley_equals_lalr():
 
 if __name__ == '__main__':
     test_python_lib()
-    # test_earley_equals_lalr()
+    test_earley_equals_lalr()
     # python_parser3.parse(_read(sys.argv[1]) + '\n')
 

lark/common.py

@@ -1,7 +1,7 @@
 import re
 import sys
 
-from .utils import get_regexp_width
+from .utils import get_regexp_width, STRING_TYPE
 
 Py36 = (sys.version_info[:2] >= (3, 6))
 
@@ -17,12 +17,13 @@ class ParseError(Exception):
     pass
 
 class UnexpectedToken(ParseError):
-    def __init__(self, token, expected, seq, index, considered_rules=None):
+    def __init__(self, token, expected, seq, index, considered_rules=None, state=None):
         self.token = token
         self.expected = expected
         self.line = getattr(token, 'line', '?')
         self.column = getattr(token, 'column', '?')
         self.considered_rules = considered_rules
+        self.state = state
 
         try:
             context = ' '.join(['%r(%s)' % (t.value, t.type) for t in seq[index:index+5]])
@@ -36,7 +37,36 @@ class UnexpectedToken(ParseError):
 
         super(UnexpectedToken, self).__init__(message)
 
-
+    def match_examples(self, parse_fn, examples):
+        """ Given a parser instance and a dictionary mapping some label with
+            some malformed syntax examples, it'll return the label for the
+            example that bests matches the current error.
+        """
+        assert self.state, "Not supported for this exception"
+
+        candidate = None
+        for label, example in examples.items():
+            assert not isinstance(example, STRING_TYPE)
+
+            for malformed in example:
+                try:
+                    parse_fn(malformed)
+                except UnexpectedToken as ut:
+                    if ut.state == self.state:
+                        if ut.token == self.token:  # Try exact match first
+                            return label
+                        elif not candidate:
+                            candidate = label
+
+        return candidate
+
+    def get_context(self, text, span=10):
+        pos = self.token.pos_in_stream
+        start = max(pos - span, 0)
+        end = pos + span
+        before = text[start:pos].rsplit('\n', 1)[-1]
+        after = text[pos:end].split('\n', 1)[0]
+        return before + after + '\n' + ' ' * len(before) + '^\n'
 ###}
 
 

lark/grammar.py

@@ -1,3 +1,32 @@
+class Symbol(object):
+    is_term = NotImplemented
+
+    def __init__(self, name):
+        self.name = name
+
+    def __eq__(self, other):
+        assert isinstance(other, Symbol), other
+        return self.is_term == other.is_term and self.name == other.name
+
+    def __ne__(self, other):
+        return not (self == other)
+
+    def __hash__(self):
+        return hash(self.name)
+
+    def __repr__(self):
+        return '%s(%r)' % (type(self).__name__, self.name)
+
+class Terminal(Symbol):
+    is_term = True
+
+    def __init__(self, name, filter_out=False):
+        self.name = name
+        self.filter_out = filter_out
+
+
+class NonTerminal(Symbol):
+    is_term = False
 
 class Rule(object):
     """
@@ -18,20 +47,14 @@ class Rule(object):
 
 
 class RuleOptions:
-    def __init__(self, keep_all_tokens=False, expand1=False, create_token=None, filter_out=False, priority=None):
+    def __init__(self, keep_all_tokens=False, expand1=False, priority=None):
         self.keep_all_tokens = keep_all_tokens
         self.expand1 = expand1
-        self.create_token = create_token  # used for scanless postprocessing
         self.priority = priority
 
-        self.filter_out = filter_out        # remove this rule from the tree
-                                            # used for "token"-rules in scanless
-
     def __repr__(self):
-        return 'RuleOptions(%r, %r, %r, %r, %r)' % (
+        return 'RuleOptions(%r, %r, %r)' % (
             self.keep_all_tokens,
             self.expand1,
-            self.create_token,
             self.priority,
-            self.filter_out
         )

lark/lark.py

@@ -3,6 +3,7 @@ from __future__ import absolute_import
 import os
 import time
 from collections import defaultdict
+from io import open
 
 from .utils import STRING_TYPE
 from .load_grammar import load_grammar
@@ -22,9 +23,9 @@ class LarkOptions(object):
                  Note: "lalr" requires a lexer
 
         lexer - Decides whether or not to use a lexer stage
-            None: Don't use a lexer (scanless, only works with parser="earley")
             "standard": Use a standard lexer
             "contextual": Stronger lexer (only works with parser="lalr")
+            "dynamic": Flexible and powerful (only with parser="earley")
             "auto" (default): Choose for me based on grammar and parser
 
         ambiguity - Decides how to handle ambiguity in the parse. Only relevant if parser="earley"
@@ -105,12 +106,12 @@ class Lark:
 
         # Some, but not all file-like objects have a 'name' attribute
         try:
-            source = grammar.name
+            self.source = grammar.name
         except AttributeError:
-            source = '<string>'
+            self.source = '<string>'
             cache_file = "larkcache_%s" % str(hash(grammar)%(2**32))
         else:
-            cache_file = "larkcache_%s" % os.path.basename(source)
+            cache_file = "larkcache_%s" % os.path.basename(self.source)
 
         # Drain file-like objects to get their contents
         try:
@@ -130,7 +131,7 @@ class Lark:
 
         if self.options.lexer == 'auto':
             if self.options.parser == 'lalr':
-                self.options.lexer = 'standard'
+                self.options.lexer = 'contextual'
             elif self.options.parser == 'earley':
                 self.options.lexer = 'dynamic'
             elif self.options.parser == 'cyk':
@@ -138,7 +139,7 @@ class Lark:
             else:
                 assert False, self.options.parser
         lexer = self.options.lexer
-        assert lexer in ('standard', 'contextual', 'dynamic', None)
+        assert lexer in ('standard', 'contextual', 'dynamic')
 
         if self.options.ambiguity == 'auto':
             if self.options.parser == 'earley':
@@ -150,10 +151,10 @@ class Lark:
         assert self.options.ambiguity in ('resolve', 'explicit', 'auto', 'resolve__antiscore_sum')
 
         # Parse the grammar file and compose the grammars (TODO)
-        self.grammar = load_grammar(grammar, source)
+        self.grammar = load_grammar(grammar, self.source)
 
         # Compile the EBNF grammar into BNF
-        tokens, self.rules, self.ignore_tokens = self.grammar.compile(lexer=bool(lexer), start=self.options.start)
+        tokens, self.rules, self.ignore_tokens = self.grammar.compile()
 
         self.lexer_conf = LexerConf(tokens, self.ignore_tokens, self.options.postlex, self.options.lexer_callbacks)
 
@@ -183,6 +184,27 @@ class Lark:
 
         return self.parser_class(self.lexer_conf, parser_conf, options=self.options)
 
+    @classmethod
+    def open(cls, grammar_filename, rel_to=None, **options):
+        """Create an instance of Lark with the grammar given by its filename
+
+        If rel_to is provided, the function will find the grammar filename in relation to it.
+
+        Example:
+
+            >>> Lark.open("grammar_file.lark", rel_to=__file__, parser="lalr")
+            Lark(...)
+
+        """
+        if rel_to:
+            basepath = os.path.dirname(rel_to)
+            grammar_filename = os.path.join(basepath, grammar_filename)
+        with open(grammar_filename) as f:
+            return cls(f, **options)
+
+    def __repr__(self):
+        return 'Lark(open(%r), parser=%r, lexer=%r, ...)' % (self.source, self.options.parser, self.options.lexer)
+
 
     def lex(self, text):
         if not hasattr(self, 'lexer'):

lark/lexer.py

@@ -43,7 +43,7 @@ class Token(Str):
         return cls(type_, value, borrow_t.pos_in_stream, line=borrow_t.line, column=borrow_t.column)
 
     def __reduce__(self):
-        return (self.__class__, (self.type, self.pos_in_stream, self.value, self.line, self.column, ))
+        return (self.__class__, (self.type, self.value, self.pos_in_stream, self.line, self.column, ))
 
     def __repr__(self):
         return 'Token(%s, %r)' % (self.type, self.value)
@@ -65,7 +65,7 @@ class LineCounter:
         self.newline_char = '\n'
         self.char_pos = 0
         self.line = 1
-        self.column = 0
+        self.column = 1
         self.line_start_pos = 0
 
     def feed(self, token, test_newline=True):
@@ -80,7 +80,7 @@ class LineCounter:
                 self.line_start_pos = self.char_pos + token.rindex(self.newline_char) + 1
 
         self.char_pos += len(token)
-        self.column = self.char_pos - self.line_start_pos
+        self.column = self.char_pos - self.line_start_pos + 1
 
 class _Lex:
     "Built to serve both Lexer and ContextualLexer"
@@ -146,6 +146,8 @@ def _create_unless(tokens):
     for retok in tokens_by_type.get(PatternRE, []):
         unless = [] # {}
         for strtok in tokens_by_type.get(PatternStr, []):
+            if strtok.priority > retok.priority:
+                continue
             s = strtok.pattern.value
             m = re.match(retok.pattern.to_regexp(), s)
             if m and m.group(0) == s:

lark/load_grammar.py

@@ -12,7 +12,8 @@ from .parse_tree_builder import ParseTreeBuilder
 from .parser_frontends import LALR
 from .parsers.lalr_parser import UnexpectedToken
 from .common import is_terminal, GrammarError, LexerConf, ParserConf, PatternStr, PatternRE, TokenDef
-from .grammar import RuleOptions, Rule
+from .grammar import RuleOptions, Rule, Terminal, NonTerminal, Symbol
+from .utils import classify, suppress
 
 from .tree import Tree, SlottedTree as ST
 from .transformers import Transformer, ChildrenTransformer, inline_args, Visitor
@@ -108,10 +109,16 @@ RULES = {
               ],
 
     '?atom': ['_LPAR expansions _RPAR',
-             'maybe',
-             'name',
-             'literal',
-             'range'],
+              'maybe',
+              'value'],
+
+    'value': ['terminal',
+              'nonterminal',
+              'literal',
+              'range'],
+
+    'terminal': ['TOKEN'],
+    'nonterminal': ['RULE'],
 
     '?name': ['RULE', 'TOKEN'],
 
@@ -146,7 +153,7 @@ class EBNF_to_BNF(ChildrenTransformer):
 
         new_name = '__%s_%s_%d' % (self.prefix, type_, self.i)
         self.i += 1
-        t = Token('RULE', new_name, -1)
+        t = NonTerminal(Token('RULE', new_name, -1))
         tree = ST('expansions', [ST('expansion', [expr]), ST('expansion', [t, expr])])
         self.new_rules.append((new_name, tree, self.rule_options))
         self.rules_by_expr[expr] = t
@@ -229,7 +236,7 @@ class RuleTreeToText(ChildrenTransformer):
     def expansions(self, x):
         return x
     def expansion(self, symbols):
-        return [sym.value for sym in symbols], None
+        return symbols, None
     def alias(self, x):
         (expansion, _alias), alias = x
         assert _alias is None, (alias, expansion, '-', _alias)  # Double alias not allowed
@@ -241,8 +248,14 @@ class CanonizeTree(ChildrenTransformer):
     def maybe(self, expr):
         return ST('expr', [expr, Token('OP', '?', -1)])
 
+    def tokenmods(self, *args):
+        if len(args) == 1:
+            return list(args)
+        tokenmods, value = args
+        return tokenmods + [value]
+
 @inline_args
-class ExtractAnonTokens(ChildrenTransformer):
+class PrepareAnonTerminals(ChildrenTransformer):
     "Create a unique list of anonymous tokens. Attempt to give meaningful names to them when we add them"
 
     def __init__(self, tokens):
@@ -257,37 +270,32 @@ class ExtractAnonTokens(ChildrenTransformer):
         if p in self.token_reverse and p.flags != self.token_reverse[p].pattern.flags:
             raise GrammarError(u'Conflicting flags for the same terminal: %s' % p)
 
+        token_name = None
+
         if isinstance(p, PatternStr):
             try:
                 # If already defined, use the user-defined token name
                 token_name = self.token_reverse[p].name
             except KeyError:
-                # Try to assign an indicative anon-token name, otherwise use a numbered name
+                # Try to assign an indicative anon-token name
                 try:
                     token_name = _TOKEN_NAMES[value]
                 except KeyError:
-                    if value.isalnum() and value[0].isalpha() and ('__'+value.upper()) not in self.token_set:
-                        token_name = '%s%d' % (value.upper(), self.i)
-                        try:
-                            # Make sure we don't have unicode in our token names
-                            token_name.encode('ascii')
-                        except UnicodeEncodeError:
-                            token_name = 'ANONSTR_%d' % self.i
-                    else:
-                        token_name = 'ANONSTR_%d' % self.i
-                    self.i += 1
-
-                token_name = '__' + token_name
+                    if value.isalnum() and value[0].isalpha() and value.upper() not in self.token_set:
+                        with suppress(UnicodeEncodeError):
+                            value.upper().encode('ascii') # Make sure we don't have unicode in our token names
+                            token_name = value.upper()
 
         elif isinstance(p, PatternRE):
             if p in self.token_reverse: # Kind of a wierd placement.name
                 token_name = self.token_reverse[p].name
-            else:
-                token_name = 'ANONRE_%d' % self.i
-                self.i += 1
         else:
             assert False, p
 
+        if token_name is None:
+            token_name = '__ANON_%d' % self.i
+            self.i += 1
+
         if token_name not in self.token_set:
             assert p not in self.token_reverse
             self.token_set.add(token_name)
@@ -295,7 +303,7 @@ class ExtractAnonTokens(ChildrenTransformer):
             self.token_reverse[p] = tokendef
             self.tokens.append(tokendef)
 
-        return Token('TOKEN', token_name, -1)
+        return Terminal(Token('TOKEN', token_name, -1), filter_out=isinstance(p, PatternStr))
 
 
 def _rfind(s, choices):
@@ -339,7 +347,7 @@ def _literal_to_pattern(literal):
 
     s = _fix_escaping(x)
 
-    if v[0] == '"':
+    if literal.type == 'STRING':
         s = s.replace('\\\\', '\\')
 
     return { 'STRING': PatternStr,
@@ -359,12 +367,6 @@ class PrepareLiterals(ChildrenTransformer):
         regexp = '[%s-%s]' % (start, end)
         return ST('pattern', [PatternRE(regexp)])
 
-@inline_args
-class SplitLiterals(ChildrenTransformer):
-    def pattern(self, p):
-        if isinstance(p, PatternStr) and len(p.value)>1:
-            return ST('expansion', [ST('pattern', [PatternStr(ch, flags=p.flags)]) for ch in p.value])
-        return ST('pattern', [p])
 
 class TokenTreeToPattern(ChildrenTransformer):
     def pattern(self, ps):
@@ -402,14 +404,19 @@ class TokenTreeToPattern(ChildrenTransformer):
     def alias(self, t):
         raise GrammarError("Aliasing not allowed in terminals (You used -> in the wrong place)")
 
-def _interleave(l, item):
-    for e in l:
-        yield e
-        if isinstance(e, Tree):
-            if e.data in ('literal', 'range'):
-                yield item
-        elif is_terminal(e):
-            yield item
+    def value(self, v):
+        return v[0]
+
+class PrepareSymbols(Transformer):
+    def value(self, v):
+        v ,= v
+        if isinstance(v, Tree):
+            return v
+        elif v.type == 'RULE':
+            return NonTerminal(v.value)
+        elif v.type == 'TOKEN':
+            return Terminal(v.value, filter_out=v.startswith('_'))
+        assert False
 
 def _choice_of_rules(rules):
     return ST('expansions', [ST('expansion', [Token('RULE', name)]) for name in rules])
@@ -420,62 +427,9 @@ class Grammar:
         self.rule_defs = rule_defs
         self.ignore = ignore
 
-    def _prepare_scanless_grammar(self, start):
-        # XXX Pretty hacky! There should be a better way to write this method..
-
-        rule_defs = deepcopy(self.rule_defs)
-        term_defs = self.token_defs
-
-        # Implement the "%ignore" feature without a lexer..
-        terms_to_ignore = {name:'__'+name for name in self.ignore}
-        if terms_to_ignore:
-            assert set(terms_to_ignore) <= {name for name, _t in term_defs}
-
-            term_defs = [(terms_to_ignore.get(name,name),t) for name,t in term_defs]
-            expr = Token('RULE', '__ignore')
-            for r, tree, _o in rule_defs:
-                for exp in tree.find_data('expansion'):
-                    exp.children = list(_interleave(exp.children, expr))
-                    if r == start:
-                        exp.children = [expr] + exp.children
-                for exp in tree.find_data('expr'):
-                    exp.children[0] = ST('expansion', list(_interleave(exp.children[:1], expr)))
-
-            _ignore_tree = ST('expr', [_choice_of_rules(terms_to_ignore.values()), Token('OP', '?')])
-            rule_defs.append(('__ignore', _ignore_tree, None))
-
-        # Convert all tokens to rules
-        new_terminal_names = {name: '__token_'+name for name, _t in term_defs}
-
-        for name, tree, options in rule_defs:
-            for exp in chain( tree.find_data('expansion'), tree.find_data('expr') ):
-                for i, sym in enumerate(exp.children):
-                    if sym in new_terminal_names:
-                        exp.children[i] = Token(sym.type, new_terminal_names[sym])
-
-        for name, (tree, priority) in term_defs:   # TODO transfer priority to rule?
-            if any(tree.find_data('alias')):
-                raise GrammarError("Aliasing not allowed in terminals (You used -> in the wrong place)")
-
-            if name.startswith('_'):
-                options = RuleOptions(filter_out=True, priority=-priority)
-            else:
-                options = RuleOptions(keep_all_tokens=True, create_token=name, priority=-priority)
-
-            name = new_terminal_names[name]
-            inner_name = name + '_inner'
-            rule_defs.append((name, _choice_of_rules([inner_name]), None))
-            rule_defs.append((inner_name, tree, options))
-
-        return [], rule_defs
-
-
-    def compile(self, lexer=False, start=None):
-        if not lexer:
-            token_defs, rule_defs = self._prepare_scanless_grammar(start)
-        else:
-            token_defs = list(self.token_defs)
-            rule_defs = self.rule_defs
+    def compile(self):
+        token_defs = list(self.token_defs)
+        rule_defs = self.rule_defs
 
         # =================
         #  Compile Tokens
@@ -491,10 +445,7 @@ class Grammar:
         # =================
 
         # 1. Pre-process terminals
-        transformer = PrepareLiterals()
-        if not lexer:
-            transformer *= SplitLiterals()
-        transformer *= ExtractAnonTokens(tokens)   # Adds to tokens
+        transformer = PrepareLiterals() * PrepareSymbols() * PrepareAnonTerminals(tokens)   # Adds to tokens
 
         # 2. Convert EBNF to BNF (and apply step 1)
         ebnf_to_bnf = EBNF_to_BNF()
@@ -520,7 +471,9 @@ class Grammar:
                 if alias and name.startswith('_'):
                     raise GrammarError("Rule %s is marked for expansion (it starts with an underscore) and isn't allowed to have aliases (alias=%s)" % (name, alias))
 
-                rule = Rule(name, expansion, alias, options)
+                assert all(isinstance(x, Symbol) for x in expansion), expansion
+
+                rule = Rule(NonTerminal(name), expansion, alias, options)
                 compiled_rules.append(rule)
 
         return tokens, compiled_rules, self.ignore
@@ -549,14 +502,14 @@ def resolve_token_references(token_defs):
     while True:
         changed = False
         for name, (token_tree, _p) in token_defs:
-            for exp in chain(token_tree.find_data('expansion'), token_tree.find_data('expr')):
-                for i, item in enumerate(exp.children):
-                    if isinstance(item, Token):
-                        if item.type == 'RULE':
-                            raise GrammarError("Rules aren't allowed inside tokens (%s in %s)" % (item, name))
-                        if item.type == 'TOKEN':
-                            exp.children[i] = token_dict[item]
-                            changed = True
+            for exp in token_tree.find_data('value'):
+                item ,= exp.children
+                if isinstance(item, Token):
+                    if item.type == 'RULE':
+                        raise GrammarError("Rules aren't allowed inside tokens (%s in %s)" % (item, name))
+                    if item.type == 'TOKEN':
+                        exp.children[0] = token_dict[item]
+                        changed = True
         if not changed:
             break
 
@@ -575,12 +528,23 @@ def options_from_rule(name, *x):
 
     return name, expansions, RuleOptions(keep_all_tokens, expand1, priority=priority)
 
+
+def symbols_from_strcase(expansion):
+    return [Terminal(x, filter_out=x.startswith('_')) if is_terminal(x) else NonTerminal(x) for x in expansion]
+
+class PrepareGrammar(InlineTransformer):
+    def terminal(self, name):
+        return name
+    def nonterminal(self, name):
+        return name
+
+
 class GrammarLoader:
     def __init__(self):
         tokens = [TokenDef(name, PatternRE(value)) for name, value in TOKENS.items()]
 
-        rules = [options_from_rule(name, x) for name, x in RULES.items()]
-        rules = [Rule(r, x.split(), None, o) for r, xs, o in rules for x in xs]
+        rules = [options_from_rule(name, x) for name, x in  RULES.items()]
+        rules = [Rule(NonTerminal(r), symbols_from_strcase(x.split()), None, o) for r, xs, o in rules for x in xs]
         callback = ParseTreeBuilder(rules, ST).create_callback()
         lexer_conf = LexerConf(tokens, ['WS', 'COMMENT'])
 
@@ -597,25 +561,34 @@ class GrammarLoader:
         except UnexpectedInput as e:
             raise GrammarError("Unexpected input %r at line %d column %d in %s" % (e.context, e.line, e.column, name))
         except UnexpectedToken as e:
-            if e.expected == ['_COLON']:
-                raise GrammarError("Missing colon at line %s column %s" % (e.line, e.column))
-            elif e.expected == ['RULE']:
-                raise GrammarError("Missing alias at line %s column %s" % (e.line, e.column))
+            context = e.get_context(grammar_text)
+            error = e.match_examples(self.parser.parse, {
+                'Unclosed parenthesis': ['a: (\n'],
+                'Umatched closing parenthesis': ['a: )\n', 'a: [)\n', 'a: (]\n'],
+                'Expecting rule or token definition (missing colon)': ['a\n', 'a->\n', 'A->\n', 'a A\n'],
+                'Alias expects lowercase name': ['a: -> "a"\n'],
+                'Unexpected colon': ['a::\n', 'a: b:\n', 'a: B:\n', 'a: "a":\n'],
+                'Misplaced operator': ['a: b??', 'a: b(?)', 'a:+\n', 'a:?\n', 'a:*\n', 'a:|*\n'],
+                'Expecting option ("|") or a new rule or token definition': ['a:a\n()\n'],
+                '%import expects a name': ['%import "a"\n'],
+                '%ignore expects a value': ['%ignore %import\n'],
+            })
+            if error:
+                raise GrammarError("%s at line %s column %s\n\n%s" % (error, e.line, e.column, context))
             elif 'STRING' in e.expected:
-                raise GrammarError("Expecting a value at line %s column %s" % (e.line, e.column))
-            elif e.expected == ['_OR']:
-                raise GrammarError("Newline without starting a new option (Expecting '|') at line %s column %s" % (e.line, e.column))
+                raise GrammarError("Expecting a value at line %s column %s\n\n%s" % (e.line, e.column, context))
             raise
 
-        # Extract grammar items
+        tree = PrepareGrammar().transform(tree)
 
-        token_defs = [c.children for c in tree.children if c.data=='token']
-        rule_defs = [c.children for c in tree.children if c.data=='rule']
-        statements = [c.children for c in tree.children if c.data=='statement']
-        assert len(token_defs) + len(rule_defs) + len(statements) == len(tree.children)
+        # Extract grammar items
+        defs = classify(tree.children, lambda c: c.data, lambda c: c.children)
+        token_defs = defs.pop('token', [])
+        rule_defs = defs.pop('rule', [])
+        statements = defs.pop('statement', [])
+        assert not defs
 
         token_defs = [td if len(td)==3 else (td[0], 1, td[1]) for td in token_defs]
-
         token_defs = [(name.value, (t, int(p))) for name, p, t in token_defs]
 
         # Execute statements
@@ -650,9 +623,11 @@ class GrammarLoader:
                 t2 ,= t.children
                 if t2.data=='expansion' and len(t2.children) == 1:
                     item ,= t2.children
-                    if isinstance(item, Token) and item.type == 'TOKEN':
-                        ignore_names.append(item.value)
-                        continue
+                    if item.data == 'value':
+                        item ,= item.children
+                        if isinstance(item, Token) and item.type == 'TOKEN':
+                            ignore_names.append(item.value)
+                            continue
 
             name = '__IGNORE_%d'% len(ignore_names)
             ignore_names.append(name)

lark/parse_tree_builder.py

@@ -1,4 +1,4 @@
-from .common import is_terminal, GrammarError
+from .common import GrammarError
 from .utils import suppress
 from .lexer import Token
 from .grammar import Rule
@@ -19,17 +19,6 @@ class ExpandSingleChild:
             return self.node_builder(children)
 
 
-class CreateToken:
-    "Used for fixing the results of scanless parsing"
-
-    def __init__(self, token_name, node_builder):
-        self.node_builder = node_builder
-        self.token_name = token_name
-
-    def __call__(self, children):
-        return self.node_builder( [Token(self.token_name, ''.join(children))] )
-
-
 class PropagatePositions:
     def __init__(self, node_builder):
         self.node_builder = node_builder
@@ -93,10 +82,11 @@ class ChildFilterLALR(ChildFilter):
         return self.node_builder(filtered)
 
 def _should_expand(sym):
-    return not is_terminal(sym) and sym.startswith('_')
+    return not sym.is_term and sym.name.startswith('_')
 
-def maybe_create_child_filter(expansion, filter_out, ambiguous):
-    to_include = [(i, _should_expand(sym)) for i, sym in enumerate(expansion) if sym not in filter_out]
+def maybe_create_child_filter(expansion, keep_all_tokens, ambiguous):
+    to_include = [(i, _should_expand(sym)) for i, sym in enumerate(expansion)
+                  if keep_all_tokens or not (sym.is_term and sym.filter_out)]
 
     if len(to_include) < len(expansion) or any(to_expand for i, to_expand in to_include):
         return partial(ChildFilter if ambiguous else ChildFilterLALR, to_include)
@@ -117,20 +107,14 @@ class ParseTreeBuilder:
         self.user_aliases = {}
 
     def _init_builders(self, rules):
-        filter_out = {rule.origin for rule in rules if rule.options and rule.options.filter_out}
-        filter_out |= {sym for rule in rules for sym in rule.expansion if is_terminal(sym) and sym.startswith('_')}
-        assert all(x.startswith('_') for x in filter_out)
-
         for rule in rules:
             options = rule.options
             keep_all_tokens = self.always_keep_all_tokens or (options.keep_all_tokens if options else False)
             expand_single_child = options.expand1 if options else False
-            create_token = options.create_token if options else False
 
             wrapper_chain = filter(None, [
-                create_token and partial(CreateToken, create_token),
                 (expand_single_child and not rule.alias) and ExpandSingleChild,
-                maybe_create_child_filter(rule.expansion, () if keep_all_tokens else filter_out, self.ambiguous),
+                maybe_create_child_filter(rule.expansion, keep_all_tokens, self.ambiguous),
                 self.propagate_positions and PropagatePositions,
             ])
 
@@ -141,9 +125,9 @@ class ParseTreeBuilder:
         callback = Callback()
 
         for rule, wrapper_chain in self.rule_builders:
-            internal_callback_name = '_callback_%s_%s' % (rule.origin, '_'.join(rule.expansion))
+            internal_callback_name = '_callback_%s_%s' % (rule.origin, '_'.join(x.name for x in rule.expansion))
 
-            user_callback_name = rule.alias or rule.origin
+            user_callback_name = rule.alias or rule.origin.name
             try:
                 f = getattr(transformer, user_callback_name)
             except AttributeError:

lark/parser_frontends.py

@@ -4,7 +4,7 @@ from .utils import get_regexp_width
 from .parsers.grammar_analysis import GrammarAnalyzer
 from .lexer import Lexer, ContextualLexer, Token
 
-from .common import is_terminal, GrammarError
+from .common import GrammarError
 from .parsers import lalr_parser, earley, xearley, resolve_ambig, cyk
 from .tree import Tree
 
@@ -17,7 +17,10 @@ class WithLexer:
         self.lexer_conf = lexer_conf
         states = {idx:list(t.keys()) for idx, t in self.parser._parse_table.states.items()}
         always_accept = lexer_conf.postlex.always_accept if lexer_conf.postlex else ()
-        self.lexer = ContextualLexer(lexer_conf.tokens, states, ignore=lexer_conf.ignore, always_accept=always_accept, user_callbacks=lexer_conf.callbacks)
+        self.lexer = ContextualLexer(lexer_conf.tokens, states,
+                                     ignore=lexer_conf.ignore,
+                                     always_accept=always_accept,
+                                     user_callbacks=lexer_conf.callbacks)
 
     def lex(self, text):
         stream = self.lexer.lex(text)
@@ -64,30 +67,6 @@ def tokenize_text(text):
             col_start_pos = i + ch.rindex('\n')
         yield Token('CHAR', ch, line=line, column=i - col_start_pos)
 
-class Earley_NoLex:
-    def __init__(self, lexer_conf, parser_conf, options=None):
-        self._prepare_match(lexer_conf)
-
-        self.parser = earley.Parser(parser_conf, self.match,
-                                    resolve_ambiguity=get_ambiguity_resolver(options))
-
-
-    def match(self, term, text, index=0):
-        return self.regexps[term].match(text, index)
-
-    def _prepare_match(self, lexer_conf):
-        self.regexps = {}
-        for t in lexer_conf.tokens:
-            regexp = t.pattern.to_regexp()
-            width = get_regexp_width(regexp)
-            if width != (1,1):
-                raise GrammarError('Scanless parsing (lexer=None) requires all tokens to have a width of 1 (terminal %s: %s is %s)' % (t.name, regexp, width))
-            self.regexps[t.name] = re.compile(regexp)
-
-    def parse(self, text):
-        token_stream = tokenize_text(text)
-        return self.parser.parse(token_stream)
-
 class Earley(WithLexer):
     def __init__(self, lexer_conf, parser_conf, options=None):
         self.init_traditional_lexer(lexer_conf)
@@ -96,7 +75,7 @@ class Earley(WithLexer):
                                     resolve_ambiguity=get_ambiguity_resolver(options))
 
     def match(self, term, token):
-        return term == token.type
+        return term.name == token.type
 
     def parse(self, text):
         tokens = self.lex(text)
@@ -117,7 +96,7 @@ class XEarley:
                                     )
 
     def match(self, term, text, index=0):
-        return self.regexps[term].match(text, index)
+        return self.regexps[term.name].match(text, index)
 
     def _prepare_match(self, lexer_conf):
         self.regexps = {}
@@ -182,9 +161,7 @@ def get_frontend(parser, lexer):
         else:
             raise ValueError('Unknown lexer: %s' % lexer)
     elif parser=='earley':
-        if lexer is None:
-            return Earley_NoLex
-        elif lexer=='standard':
+        if lexer=='standard':
             return Earley
         elif lexer=='dynamic':
             return XEarley

lark/parsers/cyk.py

@@ -8,47 +8,19 @@
 from collections import defaultdict
 import itertools
 
-from ..common import ParseError, is_terminal
+from ..common import ParseError
 from ..lexer import Token
 from ..tree import Tree
+from ..grammar import Terminal as T, NonTerminal as NT, Symbol
 
 try:
     xrange
 except NameError:
     xrange = range
 
-class Symbol(object):
-    """Any grammar symbol."""
-
-    def __init__(self, s):
-        self.s = s
-
-    def __repr__(self):
-        return '%s(%s)' % (type(self).__name__, str(self))
-
-    def __str__(self):
-        return str(self.s)
-
-    def __eq__(self, other):
-        return self.s == str(other)
-
-    def __ne__(self, other):
-        return not self.__eq__(other)
-
-    def __hash__(self):
-        return hash((type(self), str(self.s)))
-
-
-class T(Symbol):
-    """Terminal."""
-
-    def match(self, s):
-        return self.s == s.type
-
-
-class NT(Symbol):
-    """Non-terminal."""
-    pass
+def match(t, s):
+    assert isinstance(t, T)
+    return t.name == s.type
 
 
 class Rule(object):
@@ -121,10 +93,12 @@ class Parser(object):
 
     def _to_rule(self, lark_rule):
         """Converts a lark rule, (lhs, rhs, callback, options), to a Rule."""
+        assert isinstance(lark_rule.origin, NT)
+        assert all(isinstance(x, Symbol) for x in lark_rule.expansion)
         return Rule(
-            NT(lark_rule.origin), [
-                T(x) if is_terminal(x) else NT(x) for x in lark_rule.expansion
-            ], weight=lark_rule.options.priority if lark_rule.options and lark_rule.options.priority else 0, alias=lark_rule.alias)
+            lark_rule.origin, lark_rule.expansion,
+            weight=lark_rule.options.priority if lark_rule.options and lark_rule.options.priority else 0,
+            alias=lark_rule.alias)
 
     def parse(self, tokenized):  # pylint: disable=invalid-name
         """Parses input, which is a list of tokens."""
@@ -132,7 +106,7 @@ class Parser(object):
         # Check if the parse succeeded.
         if all(r.lhs != self.start for r in table[(0, len(tokenized) - 1)]):
             raise ParseError('Parsing failed.')
-        parse = trees[(0, len(tokenized) - 1)][NT(self.start)]
+        parse = trees[(0, len(tokenized) - 1)][self.start]
         return self._to_tree(revert_cnf(parse))
 
     def _to_tree(self, rule_node):
@@ -143,8 +117,8 @@ class Parser(object):
             if isinstance(child, RuleNode):
                 children.append(self._to_tree(child))
             else:
-                assert isinstance(child.s, Token)
-                children.append(child.s)
+                assert isinstance(child.name, Token)
+                children.append(child.name)
         t = Tree(orig_rule.origin, children)
         t.rule=orig_rule
         return t
@@ -169,7 +143,7 @@ def _parse(s, g):
     # Populate base case with existing terminal production rules
     for i, w in enumerate(s):
         for terminal, rules in g.terminal_rules.items():
-            if terminal.match(w):
+            if match(terminal, w):
                 for rule in rules:
                     table[(i, i)].add(rule)
                     if (rule.lhs not in trees[(i, i)] or
@@ -349,13 +323,13 @@ def revert_cnf(node):
     if isinstance(node, T):
         return node
     # Reverts TERM rule.
-    if node.rule.lhs.s.startswith('__T_'):
+    if node.rule.lhs.name.startswith('__T_'):
         return node.children[0]
     else:
         children = []
         for child in map(revert_cnf, node.children):
             # Reverts BIN rule.
-            if isinstance(child, RuleNode) and child.rule.lhs.s.startswith('__SP_'):
+            if isinstance(child, RuleNode) and child.rule.lhs.name.startswith('__SP_'):
                 children += child.children
             else:
                 children.append(child)

lark/parsers/earley.py

@@ -13,10 +13,11 @@
 # Author: Erez Shinan (2017)
 # Email : erezshin@gmail.com
 
-from ..common import ParseError, UnexpectedToken, is_terminal
 from ..tree import Tree
 from ..transformers import Transformer_InPlace
+from ..common import ParseError, UnexpectedToken
 from .grammar_analysis import GrammarAnalyzer
+from ..grammar import NonTerminal
 
 
 class Derivation(Tree):
@@ -128,7 +129,7 @@ class Column:
                     self.completed[item_key] = item
                 self.to_reduce.append(item)
             else:
-                if is_terminal(item.expect):
+                if item.expect.is_term:
                     self.to_scan.append(item)
                 else:
                     k = item_key if self.predict_all else item
@@ -162,13 +163,13 @@ class Parser:
 
     def parse(self, stream, start_symbol=None):
         # Define parser functions
-        start_symbol = start_symbol or self.parser_conf.start
+        start_symbol = NonTerminal(start_symbol or self.parser_conf.start)
 
         _Item = Item
         match = self.term_matcher
 
         def predict(nonterm, column):
-            assert not is_terminal(nonterm), nonterm
+            assert not nonterm.is_term, nonterm
             return [_Item(rule, 0, column, None) for rule in self.predictions[nonterm]]
 
         def complete(item):

lark/parsers/grammar_analysis.py

@@ -1,7 +1,7 @@
 
 from ..utils import bfs, fzset, classify
-from ..common import GrammarError, is_terminal
-from ..grammar import Rule
+from ..common import GrammarError
+from ..grammar import Rule, Terminal, NonTerminal
 
 
 class RulePtr(object):
@@ -67,7 +67,7 @@ def calculate_sets(rules):
     FIRST = {}
     FOLLOW = {}
     for sym in symbols:
-        FIRST[sym]={sym} if is_terminal(sym) else set()
+        FIRST[sym]={sym} if sym.is_term else set()
         FOLLOW[sym]=set()
 
     # Calculate NULLABLE and FIRST
@@ -108,16 +108,16 @@ class GrammarAnalyzer(object):
     def __init__(self, parser_conf, debug=False):
         self.debug = debug
 
-        rules = parser_conf.rules + [Rule('$root', [parser_conf.start, '$END'])]
+        rules = parser_conf.rules + [Rule(NonTerminal('$root'), [NonTerminal(parser_conf.start), Terminal('$END')])]
         self.rules_by_origin = classify(rules, lambda r: r.origin)
 
         assert len(rules) == len(set(rules))
         for r in rules:
             for sym in r.expansion:
-                if not (is_terminal(sym) or sym in self.rules_by_origin):
+                if not (sym.is_term or sym in self.rules_by_origin):
                     raise GrammarError("Using an undefined rule: %s" % sym) # TODO test validation
 
-        self.start_state = self.expand_rule('$root')
+        self.start_state = self.expand_rule(NonTerminal('$root'))
 
         self.FIRST, self.FOLLOW, self.NULLABLE = calculate_sets(rules)
 
@@ -125,7 +125,7 @@ class GrammarAnalyzer(object):
         "Returns all init_ptrs accessible by rule (recursive)"
         init_ptrs = set()
         def _expand_rule(rule):
-            assert not is_terminal(rule), rule
+            assert not rule.is_term, rule
 
             for r in self.rules_by_origin[rule]:
                 init_ptr = RulePtr(r, 0)
@@ -133,7 +133,7 @@ class GrammarAnalyzer(object):
 
                 if r.expansion: # if not empty rule
                     new_r = init_ptr.next
-                    if not is_terminal(new_r):
+                    if not new_r.is_term:
                         yield new_r
 
         for _ in bfs([rule], _expand_rule):
@@ -142,8 +142,8 @@ class GrammarAnalyzer(object):
         return fzset(init_ptrs)
 
     def _first(self, r):
-        if is_terminal(r):
+        if r.is_term:
             return {r}
         else:
-            return {rp.next for rp in self.expand_rule(r) if is_terminal(rp.next)}
+            return {rp.next for rp in self.expand_rule(r) if rp.next.is_term}
 

lark/parsers/lalr_analysis.py

@@ -10,9 +10,9 @@ import logging
 from collections import defaultdict
 
 from ..utils import classify, classify_bool, bfs, fzset
-from ..common import GrammarError, is_terminal
+from ..common import GrammarError
 
-from .grammar_analysis import GrammarAnalyzer
+from .grammar_analysis import GrammarAnalyzer, Terminal
 
 class Action:
     def __init__(self, name):
@@ -70,12 +70,12 @@ class LALR_Analyzer(GrammarAnalyzer):
                 rps = {rp.advance(sym) for rp in rps}
 
                 for rp in set(rps):
-                    if not rp.is_satisfied and not is_terminal(rp.next):
+                    if not rp.is_satisfied and not rp.next.is_term:
                         rps |= self.expand_rule(rp.next)
 
                 new_state = fzset(rps)
                 lookahead[sym].append((Shift, new_state))
-                if sym == '$END':
+                if sym == Terminal('$END'):
                     self.end_states.append( new_state )
                 yield new_state
 
@@ -93,7 +93,7 @@ class LALR_Analyzer(GrammarAnalyzer):
                 if not len(v) == 1:
                     raise GrammarError("Collision in %s: %s" %(k, ', '.join(['\n  * %s: %s' % x for x in v])))
 
-            self.states[state] = {k:v[0] for k, v in lookahead.items()}
+            self.states[state] = {k.name:v[0] for k, v in lookahead.items()}
 
         for _ in bfs([self.start_state], step):
             pass

lark/parsers/lalr_parser.py

@@ -2,7 +2,6 @@
 """
 # Author: Erez Shinan (2017)
 # Email : erezshin@gmail.com
-
 from ..common import UnexpectedToken
 
 from .lalr_analysis import LALR_Analyzer, Shift
@@ -47,8 +46,7 @@ class _Parser:
                 return states[state][key]
             except KeyError:
                 expected = states[state].keys()
-
-                raise UnexpectedToken(token, expected, seq, i)
+                raise UnexpectedToken(token, expected, seq, i, state=state)
 
         def reduce(rule):
             size = len(rule.expansion)
@@ -61,7 +59,7 @@ class _Parser:
 
             value = self.callbacks[rule](s)
 
-            _action, new_state = get_action(rule.origin)
+            _action, new_state = get_action(rule.origin.name)
             assert _action is Shift
             state_stack.append(new_state)
             value_stack.append(value)

lark/parsers/xearley.py

@@ -20,10 +20,11 @@
 
 from collections import defaultdict
 
-from ..common import ParseError, is_terminal
+from ..common import ParseError
 from ..lexer import Token, UnexpectedInput
 from ..tree import Tree
 from .grammar_analysis import GrammarAnalyzer
+from ..grammar import NonTerminal, Terminal
 
 from .earley import ApplyCallbacks, Item, Column
 
@@ -32,7 +33,7 @@ class Parser:
         self.analysis = GrammarAnalyzer(parser_conf)
         self.parser_conf = parser_conf
         self.resolve_ambiguity = resolve_ambiguity
-        self.ignore = list(ignore)
+        self.ignore = [Terminal(t) for t in ignore]
         self.predict_all = predict_all
 
         self.FIRST = self.analysis.FIRST
@@ -47,15 +48,15 @@ class Parser:
 
     def parse(self, stream, start_symbol=None):
         # Define parser functions
-        start_symbol = start_symbol or self.parser_conf.start
+        start_symbol = NonTerminal(start_symbol or self.parser_conf.start)
         delayed_matches = defaultdict(list)
         match = self.term_matcher
 
         text_line = 1
-        text_column = 0
+        text_column = 1
 
         def predict(nonterm, column):
-            assert not is_terminal(nonterm), nonterm
+            assert not nonterm.is_term, nonterm
             return [Item(rule, 0, column, None) for rule in self.predictions[nonterm]]
 
         def complete(item):
@@ -97,14 +98,14 @@ class Parser:
             for item in to_scan:
                 m = match(item.expect, stream, i)
                 if m:
-                    t = Token(item.expect, m.group(0), i, text_line, text_column)
+                    t = Token(item.expect.name, m.group(0), i, text_line, text_column)
                     delayed_matches[m.end()].append(item.advance(t))
 
                     s = m.group(0)
                     for j in range(1, len(s)):
                         m = match(item.expect, s[:-j])
                         if m:
-                            t = Token(item.expect, m.group(0), i, text_line, text_column)
+                            t = Token(item.expect.name, m.group(0), i, text_line, text_column)
                             delayed_matches[i+m.end()].append(item.advance(t))
 
             next_set = Column(i+1, self.FIRST, predict_all=self.predict_all)
@@ -127,7 +128,7 @@ class Parser:
 
             if token == '\n':
                 text_line += 1
-                text_column = 0
+                text_column = 1
             else:
                 text_column += 1
 

lark/tools/standalone.py

@@ -168,7 +168,7 @@ class TreeBuilderAtoms:
         print('parse_tree_builder = ParseTreeBuilder(RULES.values(), Tree)')
 
 def main(fobj, start):
-    lark_inst = Lark(fobj, parser="lalr", start=start)
+    lark_inst = Lark(fobj, parser="lalr", lexer="standard", start=start)
 
     lexer_atoms = LexerAtoms(lark_inst.parser.lexer)
     parser_atoms = ParserAtoms(lark_inst.parser.parser)

lark/tree.py

@@ -113,7 +113,6 @@ class SlottedTree(Tree):
     __slots__ = 'data', 'children', 'rule'
 
 
-
 def pydot__tree_to_png(tree, filename):
     import pydot
     graph = pydot.Dot(graph_type='digraph', rankdir="LR")

lark/utils.py

@@ -17,14 +17,15 @@ def classify_bool(seq, pred):
 
     return true_elems, false_elems
 
-def classify(seq, key=None):
+def classify(seq, key=None, value=None):
     d = {}
     for item in seq:
         k = key(item) if (key is not None) else item
+        v = value(item) if (value is not None) else item
         if k in d:
-            d[k].append(item)
+            d[k].append(v)
         else:
-            d[k] = [item]
+            d[k] = [v]
     return d
 
 def bfs(initial, expand):

tests/__main__.py

@@ -19,10 +19,10 @@ from .test_parser import (
         TestEarleyStandard,
         TestCykStandard,
         TestLalrContextual,
-        TestEarleyScanless,
+        # TestEarleyScanless,
         TestEarleyDynamic,
 
-        TestFullEarleyScanless,
+        # TestFullEarleyScanless,
         TestFullEarleyDynamic,
 
         TestParsers,

tests/test_parser.py

@@ -50,9 +50,6 @@ class TestParsers(unittest.TestCase):
 
         self.assertRaises(GrammarError, Lark, g, parser='lalr')
 
-        l = Lark(g, parser='earley', lexer=None)
-        self.assertRaises(ParseError, l.parse, 'a')
-
         l = Lark(g, parser='earley', lexer='dynamic')
         self.assertRaises(ParseError, l.parse, 'a')
 
@@ -157,7 +154,7 @@ class TestParsers(unittest.TestCase):
 
 def _make_full_earley_test(LEXER):
     class _TestFullEarley(unittest.TestCase):
-        def test_anon_in_scanless(self):
+        def test_anon(self):
             # Fails an Earley implementation without special handling for empty rules,
             # or re-processing of already completed rules.
             g = Lark(r"""start: B
@@ -166,14 +163,14 @@ def _make_full_earley_test(LEXER):
 
             self.assertEqual( g.parse('abc').children[0], 'abc')
 
-        def test_earley_scanless(self):
+        def test_earley(self):
             g = Lark("""start: A "b" c
                         A: "a"+
                         c: "abc"
                         """, parser="earley", lexer=LEXER)
             x = g.parse('aaaababc')
 
-        def test_earley_scanless2(self):
+        def test_earley2(self):
             grammar = """
             start: statement+
 
@@ -189,24 +186,19 @@ def _make_full_earley_test(LEXER):
             l.parse(program)
 
 
-        # XXX Fails for scanless mode
-        # XXX Decided not to fix, because
-        #       a) It's a subtle bug
-        #       b) Scanless is intended for deprecation
-        #
-        # def test_earley_scanless3(self):
-        #     "Tests prioritization and disambiguation for pseudo-terminals (there should be only one result)"
+        def test_earley3(self):
+            "Tests prioritization and disambiguation for pseudo-terminals (there should be only one result)"
 
-        #     grammar = """
-        #     start: A A
-        #     A: "a"+
-        #     """
+            grammar = """
+            start: A A
+            A: "a"+
+            """
 
-        #     l = Lark(grammar, parser='earley', lexer=LEXER)
-        #     res = l.parse("aaa")
-        #     self.assertEqual(res.children, ['aa', 'a'])
+            l = Lark(grammar, parser='earley', lexer=LEXER)
+            res = l.parse("aaa")
+            self.assertEqual(res.children, ['aa', 'a'])
 
-        def test_earley_scanless4(self):
+        def test_earley4(self):
             grammar = """
             start: A A?
             A: "a"+
@@ -261,7 +253,6 @@ def _make_full_earley_test(LEXER):
             assert x.data == '_ambig', x
             assert len(x.children) == 2
 
-        @unittest.skipIf(LEXER==None, "BUG in scanless parsing!")  # TODO fix bug!
         def test_fruitflies_ambig(self):
             grammar = """
                 start: noun verb noun        -> simple
@@ -352,7 +343,7 @@ def _make_full_earley_test(LEXER):
         #     assert x.data != '_ambig', x
         #     assert len(x.children) == 1
 
-    _NAME = "TestFullEarley" + (LEXER or 'Scanless').capitalize()
+    _NAME = "TestFullEarley" + LEXER.capitalize()
     _TestFullEarley.__name__ = _NAME
     globals()[_NAME] = _TestFullEarley
 
@@ -404,7 +395,6 @@ def _make_parser_test(LEXER, PARSER):
                         """)
             g.parse(u'\xa3\u0101\u00a3')
 
-        @unittest.skipIf(LEXER is None, "Regexps >1 not supported with scanless parsing")
         def test_unicode2(self):
             g = _Lark(r"""start: UNIA UNIB UNIA UNIC
                         UNIA: /\xa3/
@@ -616,11 +606,7 @@ def _make_parser_test(LEXER, PARSER):
             self.assertSequenceEqual(x.children, ['HelloWorld'])
 
 
-        @unittest.skipIf(LEXER is None, "Known bug with scanless parsing")  # TODO
         def test_token_collision2(self):
-            # NOTE: This test reveals a bug in token reconstruction in Scanless Earley
-            #       I probably need to re-write grammar transformation
-
             g = _Lark("""
                     !start: "starts"
 
@@ -664,30 +650,26 @@ def _make_parser_test(LEXER, PARSER):
             x = g.parse('aaaab')
             x = g.parse('b')
 
-        @unittest.skipIf(LEXER in (None, 'dynamic'), "Known bug with scanless parsing")  # TODO
         def test_token_not_anon(self):
-            """Tests that "a" is matched as A, rather than an anonymous token.
-
-            That means that "a" is not filtered out, despite being an 'immediate string'.
-            Whether or not this is the intuitive behavior, I'm not sure yet.
-
-            Perhaps the right thing to do is report a collision (if such is relevant)
-
-            -Erez
+            """Tests that "a" is matched as an anonymous token, and not A.
             """
 
             g = _Lark("""start: "a"
                         A: "a" """)
             x = g.parse('a')
+            self.assertEqual(len(x.children), 0, '"a" should be considered anonymous')
 
-            self.assertEqual(len(x.children), 1, '"a" should not be considered anonymous')
+            g = _Lark("""start: "a" A
+                        A: "a" """)
+            x = g.parse('aa')
+            self.assertEqual(len(x.children), 1, 'only "a" should be considered anonymous')
             self.assertEqual(x.children[0].type, "A")
 
             g = _Lark("""start: /a/
                         A: /a/ """)
             x = g.parse('a')
-            self.assertEqual(len(x.children), 1, '/a/ should not be considered anonymous')
-            self.assertEqual(x.children[0].type, "A")
+            self.assertEqual(len(x.children), 1)
+            self.assertEqual(x.children[0].type, "A", "A isn't associated with /a/")
 
         @unittest.skipIf(PARSER == 'cyk', "No empty rules")
         def test_maybe(self):
@@ -757,7 +739,6 @@ def _make_parser_test(LEXER, PARSER):
                             """)
             x = g.parse('AB')
 
-        @unittest.skipIf(LEXER == None, "Scanless can't handle regexps")
         def test_regex_quote(self):
             g = r"""
             start: SINGLE_QUOTED_STRING | DOUBLE_QUOTED_STRING
@@ -868,7 +849,6 @@ def _make_parser_test(LEXER, PARSER):
                 """
             self.assertRaises( GrammarError, _Lark, g)
 
-        @unittest.skipIf(LEXER==None, "TODO: Fix scanless parsing or get rid of it") # TODO
         def test_line_and_column(self):
             g = r"""!start: "A" bc "D"
                 !bc: "B\nC"
@@ -876,22 +856,22 @@ def _make_parser_test(LEXER, PARSER):
             l = _Lark(g)
             a, bc, d = l.parse("AB\nCD").children
             self.assertEqual(a.line, 1)
-            self.assertEqual(a.column, 0)
+            self.assertEqual(a.column, 1)
 
             bc ,= bc.children
             self.assertEqual(bc.line, 1)
-            self.assertEqual(bc.column, 1)
+            self.assertEqual(bc.column, 2)
 
             self.assertEqual(d.line, 2)
-            self.assertEqual(d.column, 1)
+            self.assertEqual(d.column, 2)
 
             if LEXER != 'dynamic':
                 self.assertEqual(a.end_line, 1)
-                self.assertEqual(a.end_column, 1)
+                self.assertEqual(a.end_column, 2)
                 self.assertEqual(bc.end_line, 2)
-                self.assertEqual(bc.end_column, 1)
+                self.assertEqual(bc.end_column, 2)
                 self.assertEqual(d.end_line, 2)
-                self.assertEqual(d.end_column, 2)
+                self.assertEqual(d.end_column, 3)
 
 
 
@@ -1056,7 +1036,6 @@ def _make_parser_test(LEXER, PARSER):
 
 
 
-        @unittest.skipIf(LEXER==None, "Scanless doesn't support regular expressions")
         @unittest.skipIf(PARSER == 'cyk', "No empty rules")
         def test_ignore(self):
             grammar = r"""
@@ -1083,7 +1062,6 @@ def _make_parser_test(LEXER, PARSER):
             self.assertEqual(tree.children, [])
 
 
-        @unittest.skipIf(LEXER==None, "Scanless doesn't support regular expressions")
         def test_regex_escaping(self):
             g = _Lark("start: /[ab]/")
             g.parse('a')
@@ -1175,10 +1153,22 @@ def _make_parser_test(LEXER, PARSER):
             self.assertRaises((ParseError, UnexpectedInput), l.parse, u'ABB')
             self.assertRaises((ParseError, UnexpectedInput), l.parse, u'AAAABB')
 
+        @unittest.skipIf(PARSER=='earley', "Priority not handled correctly right now")  # TODO XXX
+        def test_priority_vs_embedded(self):
+            g = """
+            A.2: "a"
+            WORD: ("a".."z")+
+
+            start: (A | WORD)+
+            """
+            l = _Lark(g)
+            t = l.parse('abc')
+            self.assertEqual(t.children, ['a', 'bc'])
+            self.assertEqual(t.children[0].type, 'A')
 
 
 
-    _NAME = "Test" + PARSER.capitalize() + (LEXER or 'Scanless').capitalize()
+    _NAME = "Test" + PARSER.capitalize() + LEXER.capitalize()
     _TestParser.__name__ = _NAME
     globals()[_NAME] = _TestParser
 
@@ -1189,13 +1179,13 @@ _TO_TEST = [
         ('dynamic', 'earley'),
         ('standard', 'lalr'),
         ('contextual', 'lalr'),
-        (None, 'earley'),
+        # (None, 'earley'),
 ]
 
 for _LEXER, _PARSER in _TO_TEST:
     _make_parser_test(_LEXER, _PARSER)
 
-for _LEXER in (None, 'dynamic'):
+for _LEXER in ('dynamic',):
     _make_full_earley_test(_LEXER)
 
 if __name__ == '__main__':

tests/test_trees.py

@@ -5,7 +5,7 @@ from unittest import TestCase
 import copy
 import pickle
 
-from lark.tree import Tree
+from lark.tree import Tree, Interpreter, visit_children_decor
 
 
 class TestTrees(TestCase):
@@ -21,6 +21,45 @@ class TestTrees(TestCase):
         assert pickle.loads(data) == s
 
 
+    def test_interp(self):
+        t = Tree('a', [Tree('b', []), Tree('c', []), 'd'])
+
+        class Interp1(Interpreter):
+            def a(self, tree):
+                return self.visit_children(tree) + ['e']
+
+            def b(self, tree):
+                return 'B'
+
+            def c(self, tree):
+                return 'C'
+
+        self.assertEqual(Interp1().visit(t), list('BCde'))
+
+        class Interp2(Interpreter):
+            @visit_children_decor
+            def a(self, values):
+                return values + ['e']
+
+            def b(self, tree):
+                return 'B'
+
+            def c(self, tree):
+                return 'C'
+
+        self.assertEqual(Interp2().visit(t), list('BCde'))
+
+        class Interp3(Interpreter):
+            def b(self, tree):
+                return 'B'
+
+            def c(self, tree):
+                return 'C'
+
+        self.assertEqual(Interp3().visit(t), list('BCd'))
+
+
+
 if __name__ == '__main__':
     unittest.main()