編譯器yacc作業
寫一個lex程式和一個yacc程式,
計算一些簡單的12個月收入計算:每個月薪水是底薪加獎金減預扣費用
如 jan(20000+5000-2000), feb(20000+5000-2300)
輸出
jan=23000, feb=22700
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如 jan(20000+5000-2000), feb(20000+5000-2300), mar(30000+6000-4000)
輸出
jan=23000, feb=22700, mar=32000
%{ #include "y.tab.h" %} %% [0-9]+ { yylval.ival = atoi(yytext); return NUMBER; } [ \t] ; /* ignore white space */ \n return 0; /* logical EOF */ [\+\-\(\)\,] {return yytext[0];} [a-zA-Z]+ { yylval.sval = (char *)calloc(strlen(yytext)+1,sizeof(char)); strcpy(yylval.sval,yytext); return NAME;} . ; %%
%union{ int ival; char* sval; } %token <sval> NAME %token <ival> NUMBER %type <ival> expression %start statements %% statements: statements ',' statement | statement ; statement: NAME '(' expression ')' { printf("%s=%d\n", $1, $3); free($1);} ; expression: expression '+' NUMBER { $$ = $1 + $3; } | expression '-' NUMBER { $$ = $1 - $3; } | NUMBER { $$ = $1; } ; %% main() { yyparse(); }
%union{ int ival; char* sval; } %token <sval> NAME %token <ival> NUMBER %type <ival> expression %start statement %% statement: NAME '=' expression { printf("%s=%d\n", $1, $3); free($1);} ; expression: expression '+' NUMBER { $$ = $1 + $3; } | expression '-' NUMBER { $$ = $1 - $3; } | NUMBER { $$ = $1; } ; %% main() { yyparse(); }