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How to manage part of a STRING? - Printable Version

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+---- Thread: How to manage part of a STRING? (/showthread.php?tid=836)

How to manage part of a STRING? - LukeBord1 - 01-08-2018

In standard Basic, we have this example correctly working:

Code:
10 LET a$="123456789012345678901234567890xy"
20 PRINT AT 0,0; a$
30 IF INKEY$="0" THEN LET a$=a$(32) + a$(1 TO 31)
40 GOTO 20

...but it doesn't seem to work in ZXB:

Code:
DIM test AS STRING
test="123456789012345678901234567890xy"
mainloop:
PRINT AT 0,0; test
IF INKEY="0" THEN
test=test(32) + test(1 TO 31)
END IF
GOTO mainloop

Thoughts?

Re: How to manage part of a STRING? - LukeBord1 - 01-09-2018

SOLVED by myself! :lol:

While in standard Basic the strings starts the count from "1", the ZXB syntax is "zero-based".

All works fine by simply shifting the TO values. Good...

Re: How to manage part of a STRING? - boriel - 01-09-2018

Well done! :!:
There's also another option, --string-base=1 to make the original BASIC code to work.
Also for arrays, --array-base=1

Check command line options for more flags: <!-- m --><a class="postlink" href="http://boriel.com/wiki/en/index.php/ZX_BASIC:Zxb#Command_Line_Options">http://boriel.com/wiki/en/index.php/ZX_ ... ne_Options</a><!-- m -->

Actually, for full compatibility with Sinclair BASIC, you can use --sinclair, which will enable the above plus --strict-boolean (boolean values always 0 or 1).
By default ZX BASIC uses base 0 and boolean values 0 for FALSE, and ANY other as true, because this allows better optimizations and performance.

Re: How to manage part of a STRING? - ShaunBebbers - 01-09-2019

Hello,

I am looking at string manipulation, particularly in terms of deleting the last character from a string.

My routine is as follows:

Code:
3 PRINT "Enter your number"; n$; "c:\>_";
   4 LET a$=INKEY$:
        IF a$=n$ AND b$<>"" THEN GO TO 9:
        END IF
   5 IF a$=""
        THEN GO TO 4:
        END IF
   6 IF (CODE a$=8 OR CODE a$=12)
        AND LEN(b$)>0 THEN LET a$="":
        GO SUB 2000:
        GO TO 8:
        END IF
   7 IF CODE a$<48 OR CODE a$>57
        THEN GO TO 4:
        END IF
   8 LET b$=b$+a$:
        PRINT AT 1,4; b$; "_ ":
        LET a$=INKEY$:
        GO SUB 1000:
        GO TO 4
   9 REM Rest of programme from here

The clear keyboard buffer routing is as follows:

Code:
1000 IF INKEY$<>"" THEN GO TO 1000:END IF
1001 RETURN

And the "delete last character" routine is:

Code:
2000 LET c$="":
2001 IF LEN(b$)>1
        THEN LET c$=b$(0 TO LEN(b$)-1):
        END IF
2002 LET b$=c$:
        RETURN

It's the "delete last character" routine that I'm having trouble with. the b$(0 TO LEN(b$)-1) isn't doing what I'm expecting, i.e., if the contents of b$ are:

Code:
12345

I want c$ to be:

Code:
1234

and therefore be passed back to the b$ string before returning.

Many thanks for any help or advice.

Regards,

Shaun.

Re: How to manage part of a STRING? - boriel - 02-07-2019

ShaunBebbers Wrote:Hello,

I am looking at string manipulation, particularly in terms of deleting the last character from a string.

...

It's the "delete last character" routine that I'm having trouble with. the b$(0 TO LEN(b$)-1) isn't doing what I'm expecting, i.e., if the contents of b$ are:

Code:
12345

I want c$ to be:

Code:
1234

and therefore be passed back to the b$ string before returning.

Many thanks for any help or advice.

Regards,

Shaun.

Have you tried with
Code:
b$(0 TO LEN(b$) - 2)
:?:

Since by default ZX Basic strings are 0-based (the standard in BASIC is 1-based, that is, starting from position 1), LEN(b$) - 1 is the position of the last character. So LEN(b$) - 2 is the 2nd to last.

Try this and tell me, please. :roll: