mod <→ other_mod   → -1, 0, +1, or nil

Comparison—Returns -1 if mod includes other_mod, 0 if mod is the same as other_mod, and +1 if mod is included by other_mod or if mod has no relationship with other_mod. Returns nil if other_mod is not a module.

Source Code

/*
*  call-seq:
*     mod <=> other_mod   => -1, 0, +1, or nil
*  
*  Comparison---Returns -1 if <i>mod</i> includes <i>other_mod</i>, 0 if
*  <i>mod</i> is the same as <i>other_mod</i>, and +1 if <i>mod</i> is
*  included by <i>other_mod</i> or if <i>mod</i> has no relationship with
*  <i>other_mod</i>. Returns <code>nil</code> if <i>other_mod</i> is
*  not a module.
*/

static VALUE
rb_mod_cmp(mod, arg)
   VALUE mod, arg;
{
   VALUE cmp;

   if (mod == arg) return INT2FIX(0);
   switch (TYPE(arg)) {
     case T_MODULE:
     case T_CLASS:
       break;
     default:
       return Qnil;
   }

   cmp = rb_class_inherited_p(mod, arg);
   if (NIL_P(cmp)) return Qnil;
   if (cmp) {
       return INT2FIX(-1);
   }
   return INT2FIX(1);
}