compiler

//calculator
%{
#include <stdio.h>
#include <stdlib.h>
#include "lex.yy.c"
int yywrap();
int yylex();
int yyerror(char *msg);
int flag = 0;
%}
%token N
%left '+' '-' '*' '/' '%' '(' ')'
%%
S: E { printf("Answer is : %d\n", $$); return 0; }
;
E: E'+'E {$$=$1+$3;}
| E'-'E {$$=$1-$3;}
| E'*'E {$$=$1*$3;}
| E'/'E {$$=$1/$3;}
| E'%'E {$$=$1%$3;}
| '(' E ')' {$$=$2;}
| N {$$=$1;}
;
%%
int yyerror(char *msg)
{
printf("invalid arithmetic expression\n");
flag = 1;
exit(0);
}
int main()
{
printf("enter the arithmetic operation\n");
yyparse();
if(flag==0){
printf("Valid arithmetic operation\n");
}
}

-----------------------------------
#include <stdio.h>//parse
#include <string.h>

 

// Function declarations
void S();
void F();

 

// Input string and current position
char input[100];
int position = 0;

 

// Function to check if the current symbol matches the expected symbol
int match(char symbol) {
    if (input[position] == symbol) {
        position++;
        return 1;
    }
    return 0;
}

 

// Function for non-terminal S
void S() {
    if (input[position] == '\0')
        return; // Empty production

 

    if (input[position] == '-' && input[position + 1] == '-' && input[position + 2] == '>') {
        match('-');
        match('-');
        match('>');
        F();
        S();
        F();
    }
}

 

// Function for non-terminal F
void F() {
    if (match('-') && match('-') && match('>'))
        return;

 

    if (match('<') && match('-') && match('-'))
        return;
}

 

// Main function
int main() {
    printf("Enter the input string: ");
    scanf("%s", input);

 

    S();

 

    // Check if the entire input string is parsed
    if (position == strlen(input))
        printf("Input is valid according to the grammar.\n");
    else
        printf("Input is invalid according to the grammar.\n");

 

    return 0;
}
------------------
//tree
%{

#include <stdio.h>

#include <stdlib.h>

#include "lex.yy.c"

int yywrap();

int yylex();

int yyerror(char *msg);

int flag = 0;

char st[100];

int top=0;

void A1()

{

st[top++]=yytext[0];

}

void A2()

{

printf("%c", st[--top]);

}

void A3()

{

printf("%c", yytext[0]);

}

%}

%token ID

%left '+' '-' '*' '/' '%' '(' ')' UMINUS

%%

S: E

E: E'+'{A1();}T{A2();}

| E'-'{A1();}T{A2();}

| T

;

T: T'*'{A1();}F{A2();}

| T'/'{A1();}F{A2();}

| F

;

F: '('E{A2();}')'

| '-'{A1();}F{A2();}

| ID{A3();}

;

%%

int yyerror(char *msg)

{

printf("invalid arithmetic expression\n");

flag = 1;

exit(0);

}

//driver code

int main()

{

printf("enter the arithmetic operation\n");

yyparse();

printf("\n");

}

--------------------------------