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jirsoft

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Joined: 18/09/2020
Location: Czech Republic
Posts: 533

Posted: 01:52pm 04 Apr 2021

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Hi,
I used in program for programming challenge CALL command for very simple and effective key->routine selector and found some (for me) strange behaviour:
This code is working

key$= "abc"
func$="nabc"
DO
fun$ = MID$(func$, INSTR(keys$, LCASE$(INKEY$)) + 1, 1)
CALL fun$
LOOP
END

SUB n 'empty function, needed for no key press
END SUB

SUB a
?a
END SUB

SUB b
?b
END SUB

SUB c
?c
END SUB

But when I put it all into CALL

DO
CALL MID$(func$, INSTR(keys$, LCASE$(INKEY$)) + 1, 1)
LOOP

I will get Argument list error. But some primitive string handling are working properly. Is it a bug?

Jiri
Napoleon Commander and SimplEd for CMM2 (GitHub), CMM2.fun

matherp
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Joined: 11/12/2012
Location: United Kingdom
Posts: 10310

Posted: 04:32pm 04 Apr 2021

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Quote But when I put it all into CALL
DO
CALL MID$(func$, INSTR(keys$, LCASE$(INKEY$)) + 1, 1)
LOOP

I will get Argument list error. But some primitive string handling are working properly. Is it a bug?

Check the manual. I'm surprised the first version works - certainly not by design

thwill

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Joined: 16/09/2019
Location: United Kingdom
Posts: 4311

Posted: 04:45pm 04 Apr 2021

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I'm missing something, in what way does the manual entry suggest that this wouldn't work?

Tom

MMBasic for Linux, Game*Mite, CMM2 Welcome Tape, Creaky old text adventures

matherp
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Joined: 11/12/2012
Location: United Kingdom
Posts: 10310

Posted: 04:47pm 04 Apr 2021

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Quote This is an efficient way of programmatically calling user defined subroutines

thwill

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Location: United Kingdom
Posts: 4311

Posted: 04:58pm 04 Apr 2021

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Still not getting it Peter: n, a, b & c are USER defined subroutines.

Tom

MMBasic for Linux, Game*Mite, CMM2 Welcome Tape, Creaky old text adventures

jirsoft

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Joined: 18/09/2020
Location: Czech Republic
Posts: 533

Posted: 05:13pm 04 Apr 2021

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I don't see here anything wrong

fun$ = MID$(func$, INSTR(keys$, LCASE$(INKEY$)) + 1, 1)
CALL fun$

When it will be

fun$ = "MID$(func$, INSTR(keys$, LCASE$(INKEY$)) + 1, 1)"
CALL fun$

then it will be calling built-in function.

But interesting is, when I will change it to

key$= "abc"
func$="nabc"
DO
fun$ = MID$(func$, INSTR(keys$, LCASE$(INKEY$)) + 1, 1)
CALL "f" + fun$
LOOP
END

SUB fn 'empty function, needed for no key press
END SUB

SUB fa
?a
END SUB

SUB fb
?b
END SUB

SUB fc
?c
END SUB

Then it will work OK, so some calculations are allowed in CALL...

Jiri
Napoleon Commander and SimplEd for CMM2 (GitHub), CMM2.fun

matherp
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Joined: 11/12/2012
Location: United Kingdom
Posts: 10310

Posted: 05:18pm 04 Apr 2021

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Yes but MID$ isn't so

CALL MID$(func$, INSTR(keys$, LCASE$(INKEY$)) + 1, 1)

can't work. Everything after the CALL command is interpreted as though it was normal inline code but you can't have two in-built command tokens in a row

You are correct of course about CALL fun$ that is what it is designed for - me being stupid

thwill

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Joined: 16/09/2019
Location: United Kingdom
Posts: 4311

Posted: 05:19pm 04 Apr 2021

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EDIT: written before Peter's previous response.

My guess is that the parser thinks one of the commas in MID$ or INSTR is a parameter separator in the CALL command.

But I could be talking tripe,

Tom
Edited 2021-04-05 03:22 by thwill

MMBasic for Linux, Game*Mite, CMM2 Welcome Tape, Creaky old text adventures

jirsoft

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Joined: 18/09/2020
Location: Czech Republic
Posts: 533

Posted: 05:34pm 04 Apr 2021

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Thanks Peter,
clear with more than one token. In normal life (not one page challenge

) one row more isn't problem...

I still think it's pretty effective way to select routines depending on key, you have just one condition, all function names need to have exact same length. Maximum length of func$ can be solved with LONGSTRING if needed.

Selector with 5 characters per function:

key$= "abc"
func$="emptyFUNCaFUNCbFUNCc"
DO
fun$ = MID$(func$, 5*INSTR(keys$, LCASE$(INKEY$)) + 1, 5)
CALL fun$
LOOP

SUB empty 'empty function, needed for no key press
END SUB

SUB FUNCa
?a
END SUB

SUB FUNCb
?b
END SUB

SUB FUNCc
?c
END SUB

Edited 2021-04-05 03:36 by jirsoft

Jiri
Napoleon Commander and SimplEd for CMM2 (GitHub), CMM2.fun

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