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| class Parser:
def __init__(self, token_list):
pass
# ...
def parse_expression(self):
if xxx:
self.parse_constexp()
elif yyy:
self.parse_diffexp()
#...
def parse_constexp(self):
pass
def parse_diffexp(self):
pass
def parse_zeroexp(self):
pass
def parse_ifexp(self):
pass
def parse_varexp(self):
pass
def parse_letexp(self):
pass
You can parse input such as:
input = '''let a = 0 in if zero(a) then -(a, 1) else -(a, 2)'''
tokens = list(tokenize(input))
parser = Parser(tokens)
parser.parse_program()
result is:
result = Program(
expression=Expression(
nonterminal=Letexp(
ID=Token(type='ID', value='a', line=2, column=4),
expression1=Expression(
nonterminal=Constexp(
NUMBER=Token(type='NUMBER', value='0', line=2, column=8))),
expression2=Expression(
nonterminal=Ifexp(
expression1=Expression(
nonterminal=Zeroexp(
expression=Expression(
nonterminal=Varexp(
ID=Token(type='ID', value='a', line=2, column=21))))),
expression2=Expression(
nonterminal=Diffexp(
expression1=Expression(
nonterminal=Varexp(
ID=Token(type='ID', value='a', line=2, column=31))),
expression2=Expression(
nonterminal=Constexp(
NUMBER=Token(type='NUMBER', value='1', line=2,
column=34))))),
expression3=Expression(
nonterminal=Diffexp(
expression1=Expression(
nonterminal=Varexp(
ID=Token(type='ID', value='a', line=2, column=44))),
expression2=Expression(
nonterminal=Constexp(
NUMBER=Token(type='NUMBER', value='2', line=2,
column=47))))))))))
|