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Programming-Idioms

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  • C

Idiom #43 Break outer loop

Look for a negative value v in 2D integer matrix m. Print it and stop searching.

Control flow jumping forward after the end of the outermost loop
#include <stdio.h>
int i,j;
for(i=0;i<sizeof(m)/sizeof(*m);i++)
{
	for(j=0;j<sizeof(*m)/sizeof(**m);j++)
	{
		if(m[i][j]<0)
		{
			printf("%d\n",m[i][j]);
			goto end;
		}
	}
}
end:

only works if m is allocated statically or on the stack, not if allocated in the heap.

edit: the statement above is misleading. It is referring to the use of sizeof() to set up the loops, and has nothing to do with using goto to break the loop. Using goto to break the loop will work as written, regardless of how the variables are allocated.
Outer_loop:
for A in M'Range (1) loop
   Inner_Loop:
   for B in M'Range (2) loop
      if M (A, B) < 0 then
         Put_Line (M (A, B)'Image);
         exit Outer_Loop;
      end if;
   end loop Inner_Loop;
end loop Outer_Loop;

New implementation...
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