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