Re: Creating and using arrays - again

On Fri, 21 Mar 2008, Elizabeth D Rather wrote:

>
>
> Duke Normandin wrote:
> > I've come up with something that works for me. Would you folks
critique it
> > please, and let me know any potential pitfalls.
> >
> > [23:21:03][dnormandin@[EMAIL PROTECTED]
 gforth
> > Gforth 0.6.2, Copyright (C) 1995-2003 Free Software Foundation, Inc.
> > Gforth comes with ABSOLUTELY NO WARRANTY; for details type `license'
> > Type `bye' to exit
> >
> > : } cells + ; ( addr n -- n-addr ) ok
> >   ok
> > create ages{ 10 cells allot  ok
> >   ok
> > 15 ages{ 0 } !  ok
> > 60 ages{ 1 } !  ok
> > 25 ages{ 2 } !  ok
> >   ok
> > ages{ 1 } ? 20  ok
> > cr ." I am " ages{ 1 } ? ." years old!" cr
> >
> > I'm going to make it a practice to name my arrays with a trailing { in
> > order to use the word } and have the whole thing look like something
I'm
> > used to and seems intuitive _to me_ .
> >
> > What do you think, folks?
>
> The acid test is what it looks like in a loop, since that's how most
arrays
> are used.  So, you might have:
>
> 10 CONSTANT SIZE
> CREATE DATA{  SIZE CELLS ALLOT
> : GET-DATA ( -- )   SIZE 0 DO
>    GETNUM  DATA{ I } !  LOOP ;
>
> Not bad.  Note that defining the size as a CONSTANT is useful because if
you
> reference it every time you do something with the array, you can change
the
> size just by changing this one place and recompiling.  Much better than
trying
> to find all the 10's and deciding whether this one needs changing or is
just
> 10-something-else.

Great suggestion!

> A more Forthish approach would be:
>
> : ARRAY ( n -- )   CREATE  CELLS ALLOT
>    DOES> ( i -- i-addr )   CELLS + ;

I'm just now clueing in on Forth's 'double-barrel' / 'delayed-duet'
capability of CREATE / DOES>

> 10 CONSTANT SIZE
> SIZE ARRAY MYDATA
> : GET-DATA ( -- )   SIZE 0 DO
>    GETNUM  I DATA !  LOOP ;

Is there a speed advantage in using CREATE / DOES> and burying part of the
code in the DOES> routine? Or is it simply a more "traditional" approach?
-- 
Duke Normandin
dukeofperl@[EMAIL PROTECTED]
 Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?