97 lines
2.2 KiB
Python
97 lines
2.2 KiB
Python
# -----------------------------------------------------------------------------
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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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@_('NAME "=" expression')
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def statement(self, p):
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self.names[p.NAME] = p.expression
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@_('expression')
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def statement(self, p):
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print(p.expression)
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@_('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(self, p):
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if p[1] == '+':
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return p.expression0 + p.expression1
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elif p[1] == '-':
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return p.expression0 - p.expression1
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elif p[1] == '*':
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return p.expression0 * p.expression1
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elif p[1] == '/':
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return p.expression0 / p.expression1
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@_('"-" expression %prec UMINUS')
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def expression(self, p):
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return -p.expression
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@_('"(" expression ")"')
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def expression(self, p):
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return p.expression
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@_('NUMBER')
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def expression(self, p):
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return p.NUMBER
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@_('NAME')
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def expression(self, p):
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try:
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return self.names[p.NAME]
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except LookupError:
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print("Undefined name '%s'" % p.NAME)
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return 0
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if __name__ == '__main__':
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lexer = CalcLexer()
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parser = CalcParser()
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while True:
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try:
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text = input('calc > ')
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except EOFError:
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break
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if text:
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parser.parse(lexer.tokenize(text))
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