Question

I have a very simple c code:

         #include<stdio.h>
        int main()
        {
          enum boolean{true,false};
          boolean bl=false;
          if(bl==false)
             printf("This is the false value of boool\n");
         boolean bl1=true;
          if(bl1==true)
           {
            printf("This is the true value of boool\n");
           }
    return 0;
   }

i was just trying to use enum type variable .but it is giving following error:

tryit4.c:5: error: ‘boolean’ undeclared (first use in this function)
tryit4.c:5: error: (Each undeclared identifier is reported only once
tryit4.c:5: error: for each function it appears in.)
tryit4.c:5: error: expected ‘;’ before ‘bl’
tryit4.c:6: error: ‘bl’ undeclared (first use in this function)
tryit4.c:8: error: expected ‘;’ before ‘bl1’
tryit4.c:9: error: ‘bl1’ undeclared (first use in this function)

I don’t see any reason for it. Can you please explain what could be the reason for it?

Answer 1

When you declare enum boolean { true, false }, you declare a type called enum boolean. That the name you’ll have to use after that declaration: enum boolean, not just boolean.

If you want a shorter name (like just boolean), you’ll have to define it as an alias for the original full name

typedef enum boolean boolean;

If you wish, you can declare both the enum boolean type and the boolean alias on one declaration

typedef enum boolean { true, false } boolean;