98 lines
2.0 KiB
Python
98 lines
2.0 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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# Set of token names. This is always required
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tokens = {
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'ID',
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'NUMBER',
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'PLUS',
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'MINUS',
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'TIMES',
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'DIVIDE',
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'ASSIGN',
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'LPAREN',
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'RPAREN',
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}
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# String containing ignored characters between tokens
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ignore = ' \t'
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# Regular expression rules for tokens
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ID = r'[a-zA-Z_][a-zA-Z0-9_]*'
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PLUS = r'\+'
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MINUS = r'-'
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TIMES = r'\*'
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DIVIDE = r'/'
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ASSIGN = r'='
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LPAREN = r'\('
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RPAREN = r'\)'
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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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# Get the token list from the lexer (required)
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tokens = CalcLexer.tokens
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# Grammar rules and actions
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@_('expr PLUS term')
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def expr(self, p):
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return p.expr + p.term
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@_('expr MINUS term')
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def expr(self, p):
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return p.expr - p.term
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@_('term')
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def expr(self, p):
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return p.term
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@_('term TIMES factor1')
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def term(self, p):
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return p.term * p.factor
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@_('term DIVIDE factor')
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def term(self, p):
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return p.term / p.factor
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@_('factor')
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def term(self, p):
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return p.factor
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@_('NUMBER')
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def factor(self, p):
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return p.NUMBER
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@_('LPAREN expr RPAREN')
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def factor(self, p):
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return p.expr
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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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result = parser.parse(lexer.tokenize(text))
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print(result)
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except EOFError:
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break
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