Using #define in C Program

Question

I am trying to use #define to define a constant in my program. I realize I could use const, but I am trying to get a good understanding of #define. Could someone please explain why the following code does not work, and should be done instead?

#include <stdio.h>
#define M 20;
typedef int Marray_t[M][M]; //I can't define an M x M array

int main() {
  Marray_t A;
  int i;

  for (i = 0; i < M; ++i) { //Can't iterate up to M
    A[i] = i;
  }

  return 0;
}

ThiefMaster · Accepted Answer · 2013-03-17 18:40:58Z

65

You must remove ; after20, like this

#define M 20

edited Mar 17, 2013 at 18:40

ThiefMaster

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answered Mar 17, 2013 at 18:40

nabroyan

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2 Comments

Oliver Spryn Over a year ago

Oh... it was defining it as 20;. I totally didn't think of that! Thank you.

MrMesees Over a year ago

Also if like me you are an idiot and put = assignment in define, try removing it. This shows how much I dislike defines and how I don't use C enough any more.

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