json.py

#!/usr/bin/env python

from codetalker.pgm import Grammar, Translator
from codetalker.pgm.special import star, plus, _or, commas
from codetalker.pgm.tokens import STRING, NUMBER, EOF, NEWLINE, WHITE, ReToken, re, CharToken, StringToken

'''Man this looks sweet. It really should be
this easy to write a json parser.'''

# special tokens

class SYMBOL(CharToken):
    chars = '{},[]:'
    num = 6

class TFN(StringToken):
    strings = ['true', 'false', 'null']

# rules (value is the start rule)
def value(rule):
    rule | dict_ | list_ | STRING | TFN | NUMBER
    rule.pass_single = True

def dict_(rule):
    rule | ('{', [commas((STRING, ':', value))], '}')
    rule.astAttrs = {'keys': [STRING], 'values': [value]}
dict_.astName = 'Dict'

def list_(rule):
    rule | ('[', [commas(value)], ']')
    rule.astAttrs = {'values': [value]}
list_.astName = 'List'

grammar = Grammar(start=value,
                  tokens=[SYMBOL],
                  ignore=[WHITE, NEWLINE],
                  ast_tokens=[STRING, TFN, NUMBER])

# translator stuff
JSON = Translator(grammar)

ast = grammar.ast_classes

@JSON.translates(ast.Dict)
def t_dict(node):
    return dict((JSON.translate(key), JSON.translate(value))\
                 for (key, value) in zip(node.keys, node.values))

@JSON.translates(ast.List)
def t_list(node):
    return list(JSON.translate(value) for value in node.values)

@JSON.translates(STRING)
def t_string(node):
    return node.value[1:-1].decode('string_escape')

@JSON.translates(NUMBER)
def t_number(node):
    if '.' in node.value or 'e' in node.value.lower():
        return float(node.value)
    return int(node.value)

@JSON.translates(TFN)
def t_tfn(node):
    return {'true':True, 'false':False, 'null':None}[node.value]

loads = JSON.from_string

# vim: et sw=4 sts=4