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From: rob@idacom.uucp (Rob Chapman)
Newsgroups: comp.lang.forth
Subject: Re: Use explicit arguments
Message-ID: <1991Feb4.091009.11606@idacom.uucp>
Date: 4 Feb 91 09:10:09 GMT
References: <387@rc6.urc.tue.nl>
Reply-To: rob@idacom.UUCP (Rob Chapman)
Organization: IDACOM, a dvision of HP
Lines: 38

In article <387@rc6.urc.tue.nl> wsbusup@eutws1.win.tue.nl (Jan Stout) writes:
>True enough using DO/LOOP often involves some stackacrobatics to get the
>right parameters, but then again DO/LOOP enables easier indexing 
>"in the loop" with I so will probably execute faster.
>As an example:
>
>: TYPE   SWAP OVER +
>   ?DO  I C@ EMIT LOOP ;
>instead of
>: TYPE   FOR C@+ EMIT NEXT ;
>with : C@+   1+ DUP 1- C@ ;

 This is fine for byte size cells but if you're incrementing through an array
 of CELL size cells, simply:

 : DOTS  ( a \ n -- )  FOR  @+ .  NEXT  DROP ;

  instead of any of:

 : DOTS  ( a \ n -- )  0 ?DO  DUP @ .  CELL +  LOOP ;
 : DOTS  ( a \ n -- )  0 ?DO  DUP I CELL * + @ .  LOOP ;
 : DOTS  ( a \ n -- )  CELL *  OVER + SWAP  ?DO  I @ .  CELL +LOOP ;

 I assume the stack diagram for @+ ( a -- a+ \ n ).  These incrementing fetch
 words are some of the newer "ideas" injected into the Forth domain by Chuck.
 He's had a chance to see what Forth really looks like in hardware.  These words
 usually translate to single assembler instruction, or very few.  I consider
 these words and the FOR NEXT loop to be a better factoring of indexing and
 looping functionality.

>Again I don't understand your enthousiasm for FOR/NEXT over DO/LOOP.

 There are two ways of judging a new idea:
  1. Reject it and try and find ways to substantiate your rejection (you will
     always succeed).
  2. Accept it and try it with a positive attitude.

Rob