I have been programming in PicoMite BASIC 6.02 and really enjoy it. I've been experimenting with the new STRUCT's and find them powerful.  I find that arrays of STRUCTs inside a STRUCT don't behave as I am expecting;



This works, but there are couple things that don't work the way I expect based on my experience with other languages.  When declaring an array outside of a STRUCT, you can define a CONST and use that to define the array size, but inside a STRUCT (KeyLInks), it seems like. you have to use a number.

It seems like you can't use a subscript to access a KeyLinks member:



This always seems to assign the value off T.KeyLinks(0) regardless of the subscript, but code like



Seems to work as expected.

  Mark said  

I have been programming in PicoMite BASIC 6.02 and really enjoy it. I've been experimenting with the new STRUCT's and find them powerful.  I find that arrays of STRUCTs inside a STRUCT don't behave as I am expecting;

TYPE KeyLink
 Link AS INTEGER
 Key AS STRING LENGTH 15
END TYPE

TYPE Tree
 TreeD AS INTEGER
 KeyLinks(20) AS KeyLink
END TYPE

DIM T as Tree, KL AS KeyLink
DIM L as INTEGER, K as STRING

This works, but there are couple things that don't work the way I expect based on my experience with other languages.  When declaring an array outside of a STRUCT, you can define a CONST and use that to define the array size, but inside a STRUCT (KeyLInks), it seems like. you have to use a number.

It seems like you can't use a subscript to access a KeyLinks member:

KL = T.KeyLinks(10)

This always seems to assign the value off T.KeyLinks(0) regardless of the subscript, but code like

L = T.KeyLInks(10).Link
K = T.KeyLinks(10).Key

Seems to work as expected.

I wouldn't expect T.KeyLinks(10) to work. Each KeyLinks element is made up of a Link and a Key. You have to specify which one you want when referencing KeyLinks

Thanks for responding.

What I want to do is copy both the Key and Link parts of the KeyLink STRUCT at element 10 of the KeyLinks() array to the Key and Link parts of a scalar (non array) KeyLink variable. Why don't you expect it to work? (It doesn't).

Mark

  Mark said  

I have been programming in PicoMite BASIC 6.02 and really enjoy it. I've been experimenting with the new STRUCT's and find them powerful.  I find that arrays of STRUCTs inside a STRUCT don't behave as I am expecting;

TYPE KeyLink
 Link AS INTEGER
 Key AS STRING LENGTH 15
END TYPE

TYPE Tree
 TreeD AS INTEGER
 KeyLinks(20) AS KeyLink
END TYPE

DIM T as Tree, KL AS KeyLink
DIM L as INTEGER, K as STRING

This works, but there are couple things that don't work the way I expect based on my experience with other languages.  When declaring an array outside of a STRUCT, you can define a CONST and use that to define the array size, but inside a STRUCT (KeyLInks), it seems like. you have to use a number.

Sometime during the development phase of "Structs" in MMBasic, I also had some idea, but Peter said it was impossible because the UDTs (Type .. End Type) are created in a "pre-scan phase" even before the program is finally started. Constants defined with 'CONST' are treated essentially the same way as variables, meaning they receive their value at runtime. They just can't be changed later with [LET] constName=<expression>. Therefore, it makes sense that arrays within 'Type .. End Type' must have a literal as their MaxIndex. As I see it, MS-VBA handles it the same way:

https://learn.microsoft.com/en-us/office/vba/language/reference/user-interface-help/type-statement

Surprisingly (I didn't know this), MS then switched from 'Type .. End Type' to 'Structure .. End Structure' in VB.NET, possibly to get closer to C/C++. No need to understand it — MS logic...

https://learn.microsoft.com/en-us/dotnet/visual-basic/language-reference/data-types/user-defined-data-type
https://learn.microsoft.com/en-us/dotnet/visual-basic/language-reference/statements/structure-statement

  Mark said  

It seems like you can't use a subscript to access a KeyLinks member:

KL = T.KeyLinks(10)

This always seems to assign the value off T.KeyLinks(0) regardless of the subscript, but code like

L = T.KeyLInks(10).Link
K = T.KeyLinks(10).Key

Seems to work as expected.

@Peter: This seems to be a bug - would also expect

to work..

Regards, bfwolf
Edited 2026-03-18 19:22 by bfwolf

More playing with STRUCTs.

This is just information, STRUCTs are working fine. I appreciate all the work that has gone into PicoMite BASIC. I'm treating my PicoMite as a retro computer and having a blast programming as I did (or should have) in the 1980's.

Outside of STRUCTs, BASIC doesn't like array with 1 element.



and



Both cause



But



Is fine.

However, it appears that MMBASIC treats this as if the I array has two elements.



Prints 0 and 1 as expected.



Reports the same size (16) regardless of whether you use I(0) or I(1). If I add an additional element to the STRUCT





Reports 16, regardless of I(0) or I(1).

Note, I noticed this behavior with a more complex STRUCT and simplified it for this post. These examples aren't intended to be useful code.

Thanks
Edited 2026-03-18 21:32 by Mark

Both will be fixed in next RC

Thanks for the information.