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66 rivejä
1.1 KiB
66 rivejä
1.1 KiB
%{
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/* compile: leg -o calc.c calc.leg
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* cc -o calc calc.c
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*
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* run: echo "2+3" | ./calc
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*/
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#define YYSTYPE int
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YYSTYPE yylval = 0;
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int var[26];
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%}
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start = e:exp { yylval = e }
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exp = - (a:assign { $$ = a }
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| s:sum { $$ = s }
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)
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assign = l:LETTER EQUAL n:sum { $$ = var[l - 'a'] = n }
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sum = PLUS* l:prod
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( PLUS+ r:prod { l += r }
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| MINUS r:prod { l -= r }
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)* { $$ = l }
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prod = l:neg
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( MULTI r:neg { l *= r }
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| DIVIDE r:neg { l /= r }
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| MODULO r:neg { l %= r }
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)* { $$ = l }
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neg = MINUS n:neg { $$ = -n }
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| n:value { $$ = n }
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value = n:NUMBER { $$ = n }
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| l:LETTER { $$ = var[l - 'a'] }
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- = [ \t]*
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NUMBER = < [0-9]+ > - { $$ = atoi(yytext) }
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PLUS = '+' -
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MINUS = '-' -
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MULTI = '*' -
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DIVIDE = '/' -
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MODULO = '%' -
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LETTER = (< [a-z] > { $$ = yytext[0] }
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|< [A-Z] > { $$ = yytext[0] + 'a' - 'A' }
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) -
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EQUAL = '=' -
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%%
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int main(int argc, char **argv)
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{
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while (yyparse()) {
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printf("%d\n", yylval);
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}
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/*
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for (int i = 0; i < 26; i++) {
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printf("var[%d]=%d ", i, var[i]);
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}
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*/
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return 0;
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}
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