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Improvements to decorators. Change to yacc grammar specification

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This commit is contained in:
David Beazley
2016-09-07 13:10:58 -05:00
parent 7bfadaaab3
commit a2a345e689
3 changed files with 82 additions and 77 deletions
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34
example/calc/calc.py
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@@ -42,19 +42,19 @@ class CalcParser(Parser):
def __init__(self):
self.names = { }
@_('statement : NAME "=" expression')
def statement_assign(self, p):
@_('NAME "=" expression')
def statement(self, p):
self.names[p[1]] = p[3]
@_('statement : expression')
def statement_expr(self, p):
@_('expression')
def statement(self, p):
print(p[1])
@_('''expression : expression '+' expression
| expression '-' expression
| expression '*' expression
| expression '/' expression''')
def expression_binop(self, p):
@_('expression "+" expression',
'expression "-" expression',
'expression "*" expression',
'expression "/" expression')
def expression(self, p):
if p[2] == '+':
p[0] = p[1] + p[3]
elif p[2] == '-':
@@ -64,20 +64,20 @@ class CalcParser(Parser):
elif p[2] == '/':
p[0] = p[1] / p[3]
@_('expression : "-" expression %prec UMINUS')
def expression_uminus(self, p):
@_('"-" expression %prec UMINUS')
def expression(self, p):
p[0] = -p[2]
@_('expression : "(" expression ")"')
def expression_group(self, p):
@_('"(" expression ")"')
def expression(self, p):
p[0] = p[2]
@_('expression : NUMBER')
def expression_number(self, p):
@_('NUMBER')
def expression(self, p):
p[0] = p[1]
@_('expression : NAME')
def expression_name(self, p):
@_('NAME')
def expression(self, p):
try:
p[0] = self.names[p[1]]
except LookupError: