102 lines
2.2 KiB
Python
102 lines
2.2 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 = { NAME, NUMBER, PLUS, TIMES, MINUS, DIVIDE, ASSIGN, LPAREN, RPAREN }
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ignore = ' \t'
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# Tokens
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NAME = r'[a-zA-Z_][a-zA-Z0-9_]*'
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NUMBER = r'\d+'
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# Special symbols
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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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# Ignored pattern
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ignore_newline = r'\n+'
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# Extra action for newlines
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def ignore_newline(self, t):
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self.lineno += t.value.count('\n')
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def error(self, t):
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print("Illegal character '%s'" % t.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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def __init__(self):
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self.names = { }
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@_('NAME ASSIGN expr')
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def statement(self, p):
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self.names[p.NAME] = p.expr
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@_('expr')
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def statement(self, p):
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print(p.expr)
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@_('term { PLUS|MINUS term }')
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def expr(self, p):
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lval = p.term0
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for op, rval in p[1]:
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if op == '+':
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lval = lval + rval
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elif op == '-':
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lval = lval - rval
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return lval
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@_('factor { TIMES|DIVIDE factor }')
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def term(self, p):
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lval = p.factor0
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for op, rval in p[1]:
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if op == '*':
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lval = lval * rval
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elif op == '/':
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lval = lval / rval
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return lval
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@_('MINUS factor')
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def factor(self, p):
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return -p.factor
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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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@_('NUMBER')
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def factor(self, p):
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return int(p.NUMBER)
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@_('NAME')
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def factor(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(f'Undefined name {p.NAME!r}')
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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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