4.3BSD - /usr/src/new/icon/operators/null.c

   1: #include "../h/rt.h"
   2: 
   3: /*
   4:  * /x - test x for null value.
   5:  */
   6: 
   7: null(nargs, arg1, arg0)
   8: int nargs;
   9: struct descrip arg1, arg0;
  10:    {
  11:    DclSave
  12:    SetBound;
  13: 
  14:    /*
  15:     * If x is null, it is returned, otherwise, the function fails.
  16:     *  Because the pre-dereference value of x is the return value (if
  17:     *  any), x is copied into arg0.
  18:     */
  19:    arg0 = arg1;
  20:    DeRef(arg1)
  21:    if (!NULLDESC(arg1))
  22:       fail();
  23:    ClearBound;
  24:    }
  25: 
  26: Opblock(null,1,"/")

Defined functions