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|
%{
#include <stdio.h>
#include <stdlib.h>
int yylex();
int yyerror(char *);
int loop_count = 0;
%}
%token ADD SUB MUL DIV INC DEC
%token LT GT LTE GTE EQ NEQ ASSIGN
%token FOR
%token ENDL
%token NUM ID
%start statement
%%
primary_expr: NUM
| ID
;
postfix_expr: postfix_expr INC
| postfix_expr DEC
| primary_expr
;
unary_expr: INC unary_expr
| DEC unary_expr
| postfix_expr
;
boolean_expr: unary_expr LT unary_expr
| unary_expr GT unary_expr
| unary_expr LTE unary_expr
| unary_expr GTE unary_expr
| unary_expr EQ unary_expr
| unary_expr NEQ unary_expr
;
assignment_expr: unary_expr ASSIGN unary_expr
| unary_expr ASSIGN boolean_expr
;
expression: unary_expr
| boolean_expr
| assignment_expr
;
block: '{' statement block_cont
;
block_cont: statement block_cont
| '}'
;
statement: expression ENDL
| block
| for_expr {loop_count++;}
| ENDL
;
for_expr: FOR '(' statement statement expression ')' statement
| FOR '(' statement statement ')' statement
;
%%
int main() {
yyparse();
printf("valid expression, nested %d", loop_count);
}
int yyerror(char *s) {
printf("error: %s", s);
exit(0);
}
|
