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Macros problem

This is a discussion on Macros problem within the C Programming forums, part of the General Programming Boards category; I was creating a program here Code: #include<stdio.h>#include<conio.h> #include"lib.h" void main() { clrscr(); gotoxy(0,0); HLINE(12); gotoxy(1,1); HLINE(14); getch(); } and ...

  1. #1
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    Question Macros problem

    I was creating a program here

    Code:
    #include<stdio.h>#include<conio.h>
    #include"lib.h"
    
    
    void main()
     {
      clrscr();
    
    
      gotoxy(0,0);
      HLINE(12);
      gotoxy(1,1);
      HLINE(14);
      getch();
     }
    and
    Code:
    #define HLINE(val) (for(i=0;i<=val;i++)\
    		   printf("%c",179);)
    
    it shows me 7 errors

  2. #2
    and the hat of wrongness Salem's Avatar
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    Did you see today's other question on macros?
    Help with macros
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

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    Please post those 7 errors. Copy-paste them exactly from your compiler, otherwise we can't help you.

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    @Salemyes i read the post but it is no way connected to my bug

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    Quote Originally Posted by anduril462 View Post
    Please post those 7 errors. Copy-paste them exactly from your compiler, otherwise we can't help you.
    The errors are expression syntax error at each both the occerence of HLINE, and missing statement ;

  6. #6
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    And also undefined symbol i

  7. #7
    and the hat of wrongness Salem's Avatar
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    So why are you not using the do .. while ( 0 ) trick?

    Why are you using ( ) where you should be using braces ?

    Where is i declared?
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

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    Quote Originally Posted by slain View Post
    @Salemyes i read the post but it is no way connected to my bug
    Actually, there's a really, really good chance it is very strongly connected to your bug. Salem is a smart guy and knows his stuff, he wouldn't suggest that post if he didn't think it was related. You should at least try out the suggestions from the other thread before dismissing it. Ask for clarification if you don't understand how to apply that suggestion to your code.
    Quote Originally Posted by slain View Post
    The errors are expression syntax error at each both the occerence of HLINE, and missing statement ;
    That sounds like two errors per occurrence of HLINE, and with two occurrences, that's a total of 4 errors. What about the other 3 errors? What are they?
    EDIT: Just saw your post about undeclared 'i'. That makes 5 of 7, still missing 2 errors.

    Seriously though, what is so difficult about the following request:
    Quote Originally Posted by anduril462 View Post
    Please post those 7 errors. Copy-paste them exactly from your compiler, otherwise we can't help you.
    It's very difficult for us to help you if you give faulty/incorrect/incomplete information. Furthermore, people won't want to help you if you ignore the advice or suggestions they give.
    AndiPersti and slain like this.

  9. #9
    TEIAM - problem solved
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    It's probably because you are adding a ';' at the end of HLINE() in your code

    Change your macro to what Salem suggested to fix this problem - It will allow you to use local variables as well

    Create a macro from the following. Notice that the last ';' after the "while" is omitted, so that it can be added in the actual code.
    Code:
    do
    {
      int i;
      for(...)
      {
        printf(...);
      }
    }
    while(0)
    Fact - Beethoven wrote his first symphony in C

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    @Salem Thank you for your concern and taking time to reply me, if i was rude in any way i am sorry for it.

    @anduril462 I understood the mistake i was making over there. And your post was helpful.

    and remaining people who took time to reply thank you

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    From the suggestion the error free code is
    Code:
    #include<stdio.h>
    #include<conio.h>
    #include"lib.h"
    
    
    void main()
     {
      int i =0;
      clrscr();
    
    
      gotoxy(0,0);
      HLINE(12)
      gotoxy(1,1);
      printf("\n");
      HLINE(14)
      getch();
     }
    and lib.h

    Code:
    #define HLINE(val) do{       \
    		     for(i=0;i<=val;i++)\
    		     {           \
    		     printf("%c",196); \
    		     }            \
    		     }while(0);
    Thank you for making me understanding macros better

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    Quote Originally Posted by slain View Post
    From the suggestion the error free code is
    Code:
     #define HLINE(val) do{       \
                 for(i=0;i<=val;i++)\
                 {           \
                 printf("%c",196); \
                 }            \
                 }while(0);
    It works that way but typically you leave out the final semicolon from the macro. That way in your code you can write

    HLINE(foo);

    in the normal fashion.

  13. #13
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    Even this works great !!
    Code:
    #define HLINE(val) for(i=0;i<=val;i++)\
                        {           \
                          printf("%c",196); \
                        }            
    
    Last edited by slain; 02-01-2013 at 06:52 PM.

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