Added examples (calc, json)

examples/calc.py

@@ -0,0 +1,60 @@
+from lark.tree import InlineTransformer
+from lark.lark import Lark
+
+calc_grammar = """
+    ?start: sum
+          | NAME "=" sum    -> assign_var
+
+    ?sum: product
+        | sum "+" product   -> add
+        | sum "-" product   -> sub
+
+    ?product: atom
+        | product "*" atom  -> mul
+        | product "/" atom  -> div
+
+    ?atom: /[\d.]+/         -> number
+         | "-" atom         -> neg
+         | NAME             -> var
+         | "(" sum ")"
+
+    NAME: /\w+/
+    WS.ignore: /\s+/
+"""
+
+class CalculateTree(InlineTransformer):
+    from operator import add, sub, mul, div, neg
+    number = float
+
+    def __init__(self):
+        self.vars = {}
+
+    def assign_var(self, name, value):
+        self.vars[name] = value
+        return value
+
+    def var(self, name):
+        return self.vars[name]
+
+
+
+calc_parser = Lark(calc_grammar, parser='lalr', transformer=CalculateTree())
+calc = calc_parser.parse
+
+def main():
+    while True:
+        try:
+            s = raw_input('> ')
+        except EOFError:
+            break
+        print(calc(s))
+
+def test():
+    # print calc("a=(1+2)")
+    print calc("a = 1+2")
+    print calc("1+a*-3")
+
+if __name__ == '__main__':
+    test()
+    # main()
+

examples/json_example.py

@@ -0,0 +1,64 @@
+import sys
+from lark.lark import Lark, inline_args
+from lark.tree import Transformer
+
+json_grammar = r"""
+    ?start: value
+
+    ?value: object
+          | array
+          | string
+          | number
+          | "true"             -> true
+          | "false"            -> false
+          | "null"             -> null
+
+    array  : "[" [value ("," value)*] "]"
+    object : "{" [pair ("," pair)*] "}"
+    pair   : string ":" value
+
+    number : /-?\d+(\.\d+)?([eE][+-]?\d+)?/
+    string : /".*?(?<!\\)"/
+
+    WS.ignore.newline: /[ \t\n]+/
+"""
+
+class TreeToJson(Transformer):
+    @inline_args
+    def string(self, s):
+        return s[1:-1]
+
+    array = list
+    pair = tuple
+    object = dict
+    number = inline_args(float)
+
+    null = lambda self, _: None
+    true = lambda self, _: True
+    false = lambda self, _: False
+
+json_parser = Lark(json_grammar, parser='lalr', transformer=TreeToJson())
+parse = json_parser.parse
+
+def test():
+    test_json = '''
+        {
+            "empty_object" : {},
+            "empty_array"  : [],
+            "booleans"     : { "YES" : true, "NO" : false },
+            "numbers"      : [ 0, 1, -2, 3.3, 4.4e5, 6.6e-7 ],
+            "strings"      : [ "This", [ "And" , "That" ] ],
+            "nothing"      : null
+        }
+    '''
+
+    j = parse(test_json)
+    print j
+    import json
+    assert j == json.loads(test_json)
+
+if __name__ == '__main__':
+    test()
+    with open(sys.argv[1]) as f:
+        print parse(f.read())
+