REPLSTR$() Bug (Warning LB will Hang)

[Tasp]

Warning! LB will hang and need to be forced closed if you run this.

I needed to replace the spaces in my text with double spaces. the below code makes LB hang, with the mouse pointer flickering between an arrow and hourglass. it causes 40% CPU usage and never completes. Needs to be force closed.

Both code examples create the same issue.


a$ = "If you're ever being chased by a Police dog, try not to run thru a tunnel, over a see-saw and jump thru a fiery ring, they're trained for that stuff."



a$ = replstr$(a$, " ", "  ")



PRINT a$



a$ = "If you're ever being chased by a Police dog, try not to run thru a tunnel, over a see-saw and jump thru a fiery ring, they're trained for that stuff."



b$ = replstr$(a$, " ", SPACE$(2))



PRINT b$



Change that double space to any other char and it's fine.
Change the first a$ to anything else and it still fails.

Did a search, didn't see this reported. Hope this helps.

[PaulDZ]

The reason your program is hanging is because you are changing the " " to a double " ". When the REPSTR$() command finishes with the first change, it repeats and finds the first space of the double space you just created.  One easy fix is to turn it into a two step process. First change to a different character (that wouldn't ever be part of the original string) and then change that to a double space. 

Here's an example of what I mean:


a$ = "If you're ever being chased by a Police dog, try not to run thru a tunnel, over a see-saw and jump thru a fiery ring, they're trained for that stuff."

print a$

a$ = replstr$(a$, " ", "QQ")
a$ = replstr$(a$, "QQ", "  ")

PRINT a$




Using this method will eliminate the problem.

Note: I used the character sequence "QQ" since it is NEVER used in the American English Language. In normal text, you could as easily use a CHR$(7) (ASCII BEEP) or other unprintable character if you wanted.

I hope this helps.

[Tasp]

Yep, I understand what's happening. But I reporting this as a bug, because I'm not convinced this is intended behaviour.

I would expect it to replace every " " with " ".

I assume that in Smalltalk, Carl has written this as a function that starts from the beginning of the string each time it replaces a found match, rather than continuing on from where it left off.

[Carl Gundel]

Sept 17, 2023 14:12:35 GMT -5 Tasp said:

Yep, I understand what's happening. But I reporting this as a bug, because I'm not convinced this is intended behaviour.

I would expect it to replace every " " with " ".

I assume that in Smalltalk, Carl has written this as a function that starts from the beginning of the string each time it replaces a found match, rather than continuing on from where it left off.

I think it's fair to call that a bug.

[Walt Decker]

Why use 2-step process?

'
Mstr$ = "PETER PIPER PICKED A PECK OF"
Repl$ = " "
With$ = "  "
A$ = ""

A$ = FN.ReplaceString$(Mstr$, Repl$, With$)
PRINT A$
Mstr$ = A$
Repl$ = "  "
With$ = " "
A$ = ""
A$ = FN.ReplaceString$(Mstr$, Repl$, With$)
PRINT A$
WAIT
END

FUNCTION FN.ReplaceString$(MainStr$, StrToRepl$, ReplWith$)

ReplLen = 0
WithLen = 0
Found   = 0
StrtPos = 0

TmpStr$ = ""
Lft$ = ""
Rgt$ = ""

TmpStr$ = MainStr$
ReplLen = LEN(StrToRepl$)
WithLen = LEN(ReplWith$)

StrtPos = 1
 [STRT.REPLACE]
Found = INSTR(TmpStr$, StrToRepl$, StrtPos)

IF Found THEN
 Lft$ = LEFT$(TmpStr$, Found - 1)
 Rgt$ = MID$(TmpStr$, Found + ReplLen)
 TmpStr$ = Lft$ + ReplWith$ + Rgt$
 StrtPos = Found + WithLen
 GOTO [STRT.REPLACE]
END IF

FN.ReplaceString$ = TmpStr$
END FUNCTION
'

WARNING: INSTR() is case sensitive!!!

[Brandon Parker]

Sept 17, 2023 16:34:40 GMT -5 Carl Gundel said:

Sept 17, 2023 14:12:35 GMT -5 Tasp said:

Yep, I understand what's happening. But I reporting this as a bug, because I'm not convinced this is intended behaviour.

I would expect it to replace every " " with " ".

I assume that in Smalltalk, Carl has written this as a function that starts from the beginning of the string each time it replaces a found match, rather than continuing on from where it left off.

I think it's fair to call that a bug.

This appears to be the same bug presented three years ago...

libertybasiccom.proboards.com/thread/827/replstr-single-quote


{:0)

Brandon Parker