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28 lines
663 B
Plaintext
28 lines
663 B
Plaintext
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# Grammar
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Expr <- SPACE Sum EOL { printf("%d\n", pop()); }
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/ (!EOL .)* EOL { printf("error\n"); }
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Sum <- Product ( PLUS Product { int r= pop(), l= pop(); push(l + r); }
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/ MINUS Product { int r= pop(), l= pop(); push(l - r); }
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)*
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Product <- Value ( TIMES Value { int r= pop(), l= pop(); push(l * r); }
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/ DIVIDE Value { int r= pop(), l= pop(); push(l / r); }
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)*
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Value <- NUMBER { push(atoi(yytext)); }
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/ OPEN Sum CLOSE
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# Lexemes
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NUMBER <- < [0-9]+ > SPACE
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PLUS <- '+' SPACE
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MINUS <- '-' SPACE
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TIMES <- '*' SPACE
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DIVIDE <- '/' SPACE
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OPEN <- '(' SPACE
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CLOSE <- ')' SPACE
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SPACE <- [ \t]*
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EOL <- '\n' / '\r\n' / '\r'
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