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Mark
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Joined: 26/11/2022
Location: United States
Posts: 45

Posted: 01:53pm 08 Mar 2023

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Is the only way to include non-printable characters, such as TAB and the QUOTE delimiter in a MMBasic string constant with CHR$() and concatenation?

CONST S$ = CHR$(9) + "Preceded by TAB and followed by Quote." + CHR$(34)

It appears that the + concatenation doesn't work in DATA statements. Only the part up to the first + is READ.

Thanks,
Mark

thwill

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Joined: 16/09/2019
Location: United Kingdom
Posts: 4047

Posted: 02:39pm 08 Mar 2023

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Hi Mark,

If memory serves correctly then this is a known limitation; the syntax of DATA is a bit "iffy" and doesn't evaluate string expressions, something about a need to support unquoted strings in DATA statements for backward compatibility with earlier BASIC dialects.

What I have done previously is use some combination of printable characters in the DATA and then process the strings as I read them out of the DATA section to replace with the desired non-printable characters.

Best wishes,

Tom
Edited 2023-03-09 00:41 by thwill

Game*Mite, CMM2 Welcome Tape, Creaky old text adventures

Mixtel90

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Joined: 05/10/2019
Location: United Kingdom
Posts: 6814

Posted: 02:41pm 08 Mar 2023

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That's correct. You can't have a non-printable character on screen because it's non-printable. :) (This is actually a lie. You can PRINT CHR$(240) for example.)

Your example works ok for me.

PicoMiteVGA MMBasic Version 5.07.07b20

> CONST S$ = CHR$(9) + "Preceded by TAB and followed by Quote." + CHR$(34)
> ? s$
Preceded by TAB and followed by Quote."

You can also do silly stuff like:

> a$=" an experiment "
> poke var a$,1,9
> poke var a$,15,34
> ? a$
an experiment"
>

DATA statements are a different thing.
They store:
- unquoted text under certain conditions.
- quoted text.
- numeric values.
- numeric expressions.

They don't store string expressions.
Edited 2023-03-09 00:51 by Mixtel90

Mick

Zilog Inside! nascom.info for Nascom & Gemini
Preliminary MMBasic docs & my PCB designs

CaptainBoing

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Joined: 07/09/2016
Location: United Kingdom
Posts: 2080

Posted: 03:08pm 08 Mar 2023

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DATA statements can be made dynamic with the use of a variable.

try the following

Dim Integer aa=222,n,x

Data 1,aa,3

for n=1 to 3:read x:Print x:next

Very nice.

Unfortunately, this is confined to numeric varables:

Dim Integer aa=222,n
Dim s$="fred",x$

Data "!",s$,"3"

for n=1 to 3:read x$:Print x$:next

treats the data s$ as the literal characters s and $

As an aside, String CONSTants don't need to be explicitly typed e.g. when DIMing variables, the explicit type can be omitted if basic sees the type coming so

Dim String s="fred"

is fine, but

Dim s="fred" throws an error

counter-intuitively,

Const e=Chr$(27)+"["

is fine and e is used as a string of characters with no explicit type (i.e. e$)
Edited 2023-03-09 01:13 by CaptainBoing

Mixtel90

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Joined: 05/10/2019
Location: United Kingdom
Posts: 6814

Posted: 03:11pm 08 Mar 2023

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That'd the nice thing about standards. There are so many to choose from. :)

Mick

Zilog Inside! nascom.info for Nascom & Gemini
Preliminary MMBasic docs & my PCB designs

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