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Programming-Idioms

  • Lisp
  • C#

Idiom #42 Continue outer loop

Print each item v of list a which is not contained in list b.
For this, write an outer loop to iterate on a and an inner loop to iterate on b.

Control flow jumping back to the beginning of the outermost loop
int gb = 0;
foreach (int v in a)
{
  foreach (int w in b)
  {
    gb = w;
    if (w == v)
      break;
  }
  if (gb == v)
    continue;
  System.Console.WriteLine(v);
}

This borrows from the Pascal implementation.
int *v = a;
while (v < a+N)
{
    int *w = b;
    while (w < b+M)
    {
        if (*v == *w)
            goto OUTER;
        
        ++w;
    }
    printf("%d\n", *v);
    
    OUTER: ++v;
}

N is the length of a.
M is the length of b.

Using goto is usually considered bad practice in C.

New implementation...
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