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Active Forums => QB64 Discussion => Topic started by: daro on May 17, 2021, 08:51:48 am

Title: Error with Constant comparison in SELECT CASE?
Post by: daro on May 17, 2021, 08:51:48 am
I'm finding this strange error when using a constant inside of a select case, any ideas why?
I've tried many different ways but it seems to be the use of a CONST inside of the SELECT CASE giving the error.

Expected string expression on line 12
Caused by (or after) CASE "A", 1 , "a",1 , KEY_ARROW_LEFT


Code: QB64: [Select]
  1. Const KEY_ARROW_LEFT = Chr$(0) + Chr$(72)
  2. Const KEY_ARROW_UP = Chr$(0) + Chr$(72)
  3. Const KEY_ARROW_RIGHT = Chr$(0) + Chr$(77)
  4. Const KEY_ARROW_DOWN = Chr$(0) + Chr$(80)
  5. Const KEY_PAGE_UP = Chr$(0) + Chr$(73)
  6. Const KEY_PAGE_DOWN = Chr$(0) + Chr$(81)
  7.  
  9.  
  10.     keyp$ = InKey$
  11.     Select Case keyp$
  12.         Case "A", "a", KEY_ARROW_LEFT
  13.             Print " Left ";
  14.         Case "W", "w", KEY_ARROW_UP
  15.             Print " Up   ";
  16.         Case "D", "d" , KEY_ARROW_RIGHT
  17.             Print " Right";
  18.         Case "S", "s", KEY_ARROW_DOWN
  19.             Print " Down ";
  20.         Case "Z", "z", KEY_PAGE_DOWN
  21.             Print " P.Up ";
  22.         Case "X","x", KEY_PAGE_UP
  23.             Print "P.Down ";
  24.         Case KEY_ESCAPE
  25.             Exit Do
  26.     End Select
  27.  
Title: Re: Error with Constant comparison in SELECT CASE?
Post by: FellippeHeitor on May 17, 2021, 09:56:15 am
@daro Looks indeed like a bug. We'll have a look.

In the meantime, make those DIM SHARED AS STRING instead of CONSTs, for the same expected effect:

Code: QB64: [Select]
  1. DIM SHARED AS STRING KEY_ARROW_LEFT, KEY_ARROW_UP, KEY_ARROW_RIGHT, KEY_ARROW_DOWN, KEY_PAGE_UP, KEY_PAGE_DOWN
  2. KEY_ARROW_LEFT = Chr$(0) + Chr$(72)
  3. KEY_ARROW_UP = Chr$(0) + Chr$(72)
  4. KEY_ARROW_RIGHT = Chr$(0) + Chr$(77)
  5. KEY_ARROW_DOWN = Chr$(0) + Chr$(80)
  6. KEY_PAGE_UP = Chr$(0) + Chr$(73)
  7. KEY_PAGE_DOWN = Chr$(0) + Chr$(81)
  8.  

Welcome aboard.
Title: Re: Error with Constant comparison in SELECT CASE?
Post by: Cobalt on May 17, 2021, 02:31:06 pm
I would recommend using _KEYHIT or _KEYDOWN over INKEY$ and changing that SELECT CASE into IF THENs.


@FellippeHeitor
Doesn't CONST have issues when using variables as assignments?
Wasn't there something not that long ago about using a variable to assign constant?
something like:
A%=15-3
CONST VALUE = A%

I can't quite remember now. not having any luck with the search either, but I could swear we've had something like this before.
Title: Re: Error with Constant comparison in SELECT CASE?
Post by: bplus on May 17, 2021, 02:36:39 pm
Quote from: Cobalt on May 17, 2021, 02:31:06 pm
I would recommend using _KEYHIT or _KEYDOWN over INKEY$ and changing that SELECT CASE into IF THENs.


@FellippeHeitor
Doesn't CONST have issues when using variables as assignments?
Wasn't there something not that long ago about using a variable to assign constant?
something like:
A%=15-3
CONST VALUE = A%

I can't quite remember now. not having any luck with the search either, but I could swear we've had something like this before.

We've had trouble using Functions and doing math but I think it's been fixed. Maybe not all string stuff is, I think we are using Steve Math Evaluator?
Title: Re: Error with Constant comparison in SELECT CASE?
Post by: FellippeHeitor on May 21, 2021, 08:09:26 pm
Turns out the CONST evaluator was never meant to be used with string functions, like Chr$, Space$, etc. - but Chr$ had been left there as valid - just a slip. The latest dev build generated today fixes that by not allowing string functions in CONSTs. This is a list of the functions that can be used in CONSTs. The wiki page for CONST is getting updated too.

Code: QB64: [Select]
Title: Re: Error with Constant comparison in SELECT CASE?
Post by: FellippeHeitor on May 21, 2021, 08:30:00 pm
Quote from: Cobalt on May 17, 2021, 02:31:06 pm
I would recommend using _KEYHIT or _KEYDOWN over INKEY$ and changing that SELECT CASE into IF THENs.


@FellippeHeitor
Doesn't CONST have issues when using variables as assignments?
Wasn't there something not that long ago about using a variable to assign constant?
something like:
A%=15-3
CONST VALUE = A%

I can't quite remember now. not having any luck with the search either, but I could swear we've had something like this before.

It was never really allowed with variables, but we did have a problem recently (fixed in 1.5) that would cause issues when referencing existing CONSTs in a new CONST assignment.
Title: Re: Error with Constant comparison in SELECT CASE?
Post by: bplus on May 22, 2021, 10:46:42 am
edit: OP wanted strings not numbers
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