🚀 go-pugleaf

In article <441@unisoft.UUCP> jef@unisoft.UUCP (Jef Poskanzer) writes:
>int p1(x)
>int x;
>    {
>    return x + 1;
>    }
>
>Or if you want to be polymorphic:
>
>#define p1(x) ((x) + 1)

These aren't higher order functions.  In Doug Pase's example, plus was the
higher order function, not p1.  It's hard to explain what plus does to a C
programmer because C can't express it.  Here's a stab at explaining what
plus does using a mix of Pascal and C and illegal syntax:

    function plus (y : number) : (function __ (__ : number): number);
      function p1 (x : number) : number;
        begin
          return x + y
        end;
      begin
        return p1
      end

The key thing to observe is that the function p1 must remember the value of
y that was in effect when it was created, even after the plus function has
returned.  This is why stack-based languages like Pascal and C don't support
higher order functions.

Peace, Will Clinger
Tektronix Computer Research Lab