97 lines
2.3 KiB
Python
97 lines
2.3 KiB
Python
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# -----------------------------------------------------------------------------
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# calc.py
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# -----------------------------------------------------------------------------
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import sys
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sys.path.insert(0, "../..")
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from sly import Lexer, Parser
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class CalcLexer(Lexer):
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tokens = (
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'NAME', 'NUMBER',
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)
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ignore = ' \t'
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literals = ['=', '+', '-', '*', '/', '(', ')']
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# Tokens
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NAME = r'[a-zA-Z_][a-zA-Z0-9_]*'
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@_(r'\d+')
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def NUMBER(self, t):
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t.value = int(t.value)
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return t
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@_(r'\n+')
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def newline(self, t):
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self.lineno += t.value.count('\n')
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def error(self, value):
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print("Illegal character '%s'" % value[0])
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self.index += 1
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class CalcParser(Parser):
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tokens = CalcLexer.tokens
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precedence = (
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('left', '+', '-'),
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('left', '*', '/'),
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('right', 'UMINUS'),
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)
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def __init__(self):
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self.names = { }
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@_('statement : NAME "=" expression')
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def statement_assign(self, p):
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self.names[p[1]] = p[3]
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@_('statement : expression')
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def statement_expr(self, p):
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print(p[1])
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@_('''expression : expression '+' expression
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| expression '-' expression
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| expression '*' expression
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| expression '/' expression''')
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def expression_binop(self, p):
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if p[2] == '+':
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p[0] = p[1] + p[3]
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elif p[2] == '-':
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p[0] = p[1] - p[3]
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elif p[2] == '*':
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p[0] = p[1] * p[3]
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elif p[2] == '/':
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p[0] = p[1] / p[3]
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@_('expression : "-" expression %prec UMINUS')
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def expression_uminus(self, p):
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p[0] = -p[2]
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@_('expression : "(" expression ")"')
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def expression_group(self, p):
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p[0] = p[2]
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@_('expression : NUMBER')
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def expression_number(self, p):
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p[0] = p[1]
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@_('expression : NAME')
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def expression_name(self, p):
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try:
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p[0] = self.names[p[1]]
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except LookupError:
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print("Undefined name '%s'" % p[1])
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p[0] = 0
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if __name__ == '__main__':
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parser = CalcParser()
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while True:
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try:
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s = input('calc > ')
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except EOFError:
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break
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if s:
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parser.parse(CalcLexer(s))
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