DBP - Weird Compilation Error - Bug?

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Chris66

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Posted: 10th Dec 2010 16:28 Edited at: 11th Dec 2010 00:22

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Hi there,

I'am using DBP 7.5

Compiling the code below send back this error :

Quote: "Cannot declare 'BYTE' twice ar line 96"

+ Code Snippet


26   Tile_Depth as BYTE = 0

//   I Removed lines [27-92] for this post

93   If I$="B"
94       Tile_Depth = 8 : Global Dim Map(Map_W,Map_Y) as BYTE
95   Else
96       Tile_Depth = 16 : Global Dim Map(Map_W,Map_Y) as WORD
97   EndIf

And compiling these ones (slightly modifications) works perfectly...

+ Code Snippet


26   Tile_Depth as BYTE = 0

//   I Removed lines [27-92] for this post

93   If I$="B"
94       Tile_Depth = 8
95       Global Dim Map(Map_W,Map_Y) as BYTE
96   Else
97       Tile_Depth = 16
98       Global Dim Map(Map_W,Map_Y) as WORD
99   EndIf

The code below works too.

+ Code Snippet


If I$="B"
    Tile_Depth = 8
    Global Dim Map(Map_W,Map_Y) as BYTE
Else
    Tile_Depth = 16 : Global Dim Map(Map_W,Map_Y) as WORD
EndIf

And this latest one works fine too.

+ Code Snippet


If I$="B"
    Tile_Depth = 8 : Global Dim Map(Map_W,Map_Y) as BYTE
Else
    Tile_Depth = 16
    Global Dim Map(Map_W,Map_Y) as WORD
EndIf

I would like to understand if I made a mistake into the 1st version of the code (using ':'?) or if the error is related to a bug of the compiler.

Thanks.

Cheers,
Chris

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Green Gandalf

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Posted: 10th Dec 2010 18:45

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Quote: " or if the error is related to a bug of the compiler"

Looks like it. I can confirm the symptoms you describe - but I'm not convinced any version works the way you expect. If I recall correctly conditional compilation code sometimes compiles and sometimes doesn't. I forget the details.

You'll have to wait for IanM to look at this.

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IanM

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Posted: 10th Dec 2010 23:44

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That's not conditional compilation - therr's a runtime conditional in there though.

Basically, none of that code should compile. You shouldn't be able to DIM an array to multiple types - DBPro uses static typing, which basically means that all types are fixed at compile time, and in each of those pieces of code, it's being told that the array has two different types.

So yes there's a bug, but it's not the bug you think it is.

In the meantime, pick a type that covers both number ranges (basically, it's WORD), and DIM the array once.

One the other subject, conditional compilation can be done in DBPro, but not with the standard IF statement - you have to play some pretty unreadable tricks with the #CONSTANT keyword.

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Chris66

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Posted: 11th Dec 2010 00:21 Edited at: 11th Dec 2010 00:25

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Hi,

Quote: "That's not conditional compilation - therr's a runtime conditional in there though."

Yes, Indeed.

Quote: "DBPro uses static typing, which basically means that all types are fixed at compile time..."

It's an important information I didn't know, thanks!

Quote: "So yes there's a bug, but it's not the bug you think it is."

Well my problem was with the weird compilation behaviour related to the place of the commands, not with the error I made using the Dim instruction... as I didn't know there was an error at this point : call me jar jar binks.

Quote: "In the meantime, pick a type that covers both number ranges (basically, it's WORD), and DIM the array once."

It looks like to be the easier way, thanks again.

Cheers,
Chris

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Green Gandalf

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Posted: 11th Dec 2010 00:35

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Quote: "That's not conditional compilation - therr's a runtime conditional in there though."

Oops - not quite what I meant to say, "conditional runtime declaration" would be closer to what I meant.

Quote: "One the other subject, conditional compilation can be done in DBPro, but not with the standard IF statement - you have to play some pretty unreadable tricks with the #CONSTANT keyword."

Sounds like something best avoided.

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Chris66

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Posted: 11th Dec 2010 01:27 Edited at: 11th Dec 2010 12:15

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Hi again,

A precision to avoid confusion and misunderstood :

Quote: "Basically, none of that code should compile. You shouldn't be able to DIM an array to multiple types "

In fact, in the code I provided in the 1st post the 2 variables Map_W & Map_Y are the same type which is WORD (sorry I didn't give that precision).
So, what I'am trying to do with this code is to declare a 2 dimentional array using variables.

Here is a more complete version of the previous code :

+ Code Snippet

25   Global Map_W as WORD = 0 : Global Map_Y as WORD = 0
26   Tile_Depth as BYTE = 0

//   I Removed lines [27-92] for this post

//   I let the user define the values he wants for Map_W and Map_Y
//   Let's say Map_W=600 and Map_Y=400
//   Then I want to create the Map array as BYTE or WORD depending the Tile_Depth format the user choosed too (BYTE or WORD) :


93   If I$="B"
94       Tile_Depth = 8 : Global Dim Map(Map_W,Map_Y) as BYTE
95   Else
96       Tile_Depth = 16 : Global Dim Map(Map_W,Map_Y) as WORD
97   EndIf

BTW

Just to be sure that I've understood how to use the DIM command correctly...

Please, can you tell me if this piece of code is correct ?

+ Code Snippet


Global Map_Format as Byte = 0    
Global Map_W as Word = 600       // Map Width
Global Map_H as Word = 300       // Map Heigth

[...] // Other piece of code will be here

If I$="B"
   Map_Format=8         // If 8 bits mode is selected then I'll use this array
   Global Dim Map_08(Map_W,Map_H) as BYTE
Else
   Map_Format=16        // If 16 bits mode is selected then I'll use this array instead
   Global Dim Map_16(Map_W,Map_H) as WORD
EndIf

Thanks in advance!

Cheers,
Chris

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IanM

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Posted: 11th Dec 2010 12:13

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That's fine, but you are making work for yourself, having to write the same code once for each array. My advice is to use a single WORD array for both BYTE and WORD data.

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Chris66

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Posted: 11th Dec 2010 12:49 Edited at: 11th Dec 2010 12:58

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Thank you very much IanM!

Quote: "That's fine, but you are making work for yourself, having to write the same code once for each array. My advice is to use a single WORD array for both BYTE and WORD data."

You are right, this is not a good approach I made. So I modified the code this way using your advice :

I assume this is a wrong way to do (because I'am using a same array name in both DIM lines?)... but I definitely like this would be possible

:

+ Code Snippet


Global Map_Format as Byte = 0    
Global Map_W as Word = 600       // Map Width
Global Map_H as Word = 300       // Map Heigth

[...] // Other piece of code will be here

If I$="B"
   Map_Format=8         // If 8 bits mode is selected then I'll define the array as BYTE
   Global Dim Map(Map_W,Map_H) as BYTE
Else
   Map_Format=16        // If 16 bits mode is selected then I'll define the array as WORD
   Global Dim Map(Map_W,Map_H) as WORD
EndIf

The right way should be this one :

+ Code Snippet


Global Map_W as Word = 600       // Map Width
Global Map_H as Word = 300       // Map Heigth

[...] // Other piece of code will be here

Global Dim Map(Map_W,Map_H) as Word

Cheers
Chris

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Mobiius

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Posted: 16th Dec 2010 17:27

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Also,

Quote: "Global Dim ..."

You don't need go global dim variables. Dimmed variables are global anyway, even ones declared inside functions.

My signature is NOT a moderator plaything! Stop changing it!

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Chris66

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Posted: 17th Dec 2010 11:09 Edited at: 22nd Dec 2010 01:25

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Thanks Mobiius, so it seems I misunderstood what's explained into the "Data Types, Variables and Arrays" chapter of the help file.

Edit :

I made some tests and Local Dim declaration works fine when they are used into functions.

But indeed a Dim declaration made into the Main code (before "End") doesn't need to be declared as "Global".

+ Code Snippet


Test()                     // Works fine

//Print Test_Value(2,1)   // Of course, trying to compile the code including this command will crash at compilation.
                          // but don't trying to access Local Dims from out of their functions (which would be illogical)
                          // works perfectly.

End


// ------------------ Test --------------------

Function Test()

Local Dim Test_Value(2,2)
Test_Value(1,1) = 2 : Test_Value(1,2) = 4 : Test_Value(2,1) = 8 : Test_Value(2,2) = 16

Print Test_Value(2,1) : Sync : Wait Key

// Do your Stuff here...

// Undim Test_Value() : This will be necessary for correct code, but unsued here for the purpose of
                        // the test (when trying to compile with the "Print... " line of code).

Endfunction

Cheers,

Chris

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Bug Reports / DBP - Weird Compilation Error - Bug?