[Coco] Back to DEF FN

[Arthur Flexser]

Aaron, what does that "array search disable" do?   I'm guessing that if you
define FN(B)=B+3, that the array search disable means it makes no
difference if the dummy variable B happens to be the name of a declared
array or not.  Is that correct?

Art


On Tue, Jan 28, 2014 at 12:29 PM, Aaron Wolfe <aawolfe at gmail.com> wrote:

> Extended Basic Unravelled contains a detailed disassembly of the DEF
> code.  Here is the relevant bit:
>
>
> 1015 8880 BD B2 6A // JSR LB26A
>     SYNTAX CHECK FOR '('
>
> 1016 8883 C6 80 // LDB #$80
>    GET THE FLAG TO INDICATE ARRAY VARIABLE SEARCH DISABLE
>
> 1017 8885 D7 08  // STB ARYDIS
>    AND SAVE IT IN THE ARRAY DISABLE FLAG
>
> 1018 8887 BD B3 57 // JSR LB357
>    GET VARIABLE DESCRIPTOR
>
> 1019 888A 8D 25 // BSR L88B1
>    'TM' ERROR IF STRING
>
> 1020 888C BD B2 67 // JSR LB267
>    SYNTAX CHECK FOR ')'
>
> As you can see, there is no loop or any other mechanism that might
> allow more than a single variable to be parsed.
> The docs might be inconsistent or confusing, but the code is clear.
>
> -Aaron
>
>
> On Mon, Jan 27, 2014 at 7:37 PM, Rogelio Perea <os9dude at gmail.com> wrote:
> > Just got delivered a library copy of Peter Vernon's "Making The Mos of
> Your
> > TRS-80 Color Computer", it was the bargain bin on Amazon (Prentice-Hall
> > Australia 1983 ISBN 0 7248 0752 7).
> >
> > Leafing through the pages I came to the section where each ECB command is
> > listed, an odd wording of the old DEF FN caught my eye:
> >
> > 10 DEF FN( A B C)=(A+B+C)/3
> > 20 INPUT"ENTER THREE NUMBERS";A,B,C
> > 30 D=FNA(A B C)
> > 40 PRINT"THE AVERAGE IS";D
> > 50 PRINT
> > 60 GOTO 20
> >
> > I was perplexed for a bit. Could it be that the proper syntax on the
> CoCo's
> > DEF FN requires the variables to be separated by a space instead of a
> > comma? could it be *that* simple?
> >
> > I retyped the MOD routine into the CoCo as:
> >
> > 10 DEF FNRE=(N1 N2)=N1-INT(N1/N2)*N2
> > 20 CLS
> > 30 INPUT"NUMBER 1";N1
> > 40 INPUT"NUMBER 2";N2
> > 50 PRINT
> > 60 PRINT N1;"MOD";N2;"IS";FNRE(N1 N2)
> > 70 PRINT
> > 80 GOTO 30
> >
> > And it worked. This routine above is based on one shown by Lewis
> > Rosenfelder in "Basic Faster And Better & Other Mysteries" book. I was
> on a
> > roll and ported another one from Rosenfelder's (date day # finder):
> >
> > 10 CLS
> > 20 DEF FNJD(Y M
> > D)=(M-1)*28+VAL(MID$("000303060811131619212426",(M-1)*2+1,2))-((M>2) AND
> > ((Y AND NOT -4)=0))+D
> > 30 INPUT"YEAR (1901-2099)";Y
> > 40 INPUT"MONTH (1-12)";M
> > 50 INPUT"DAY (1-31)";D
> > 60 PRINT
> > 70 PRINT"THAT IS THE";FNJD(Y M D);"DAY OF THE YEAR"
> > 80 PRINT
> > 90 END
> >
> > Still smiling as I type this. The CoCo ECB book sins in being sparse at
> > best on covering one of the most underrated functions in the BASIC
> > repertoire, one that can come useful if applied properly. It had been
> years
> > (decades actually) since the first time I fiddled with DEF FN and it was
> > disappointing back then that I could not get it to work with 2 or more
> > arguments... I was using the syntax I knew from the TRS-80 Model I and
> III
> > BASIC separating the arguments by commas.
> >
> > With all this, the CoCo's DEF FN is still limited to numeric functions as
> > far as I know; ran a routine trying to define a string variable function
> > (simple concatenation) and the CoCo returned a type mismatch error. Oh
> > well, having this found to work with multiple variable arguments is in my
> > eye *the* discovery of the 21st century. Old ECB CoCo style :-)
> >
> >
> > -- RP
> >
> > --
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> > Coco at maltedmedia.com
> > http://five.pairlist.net/mailman/listinfo/coco
>
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