Promotional Modifiers

[Timbo]

Hi,

I'm new to firewing at the language syntax in general, reading the manual I have come across "Promotional Modifiers"

Variable Type Legal
Â
Byte, SByte, Char AsUShort,
UShort, Short


Promotional Modifiers
Â
AsShort, AsUInteger, AsInteger, AsSingle
AsUInteger, AsInteger, AsSingle

Now my question is what exactly does it do and how is it used?

Thanks

[David John Barker]

Promotional modifiers "promote" a value (for example, a byte varaible) to a word or long word value. For example

Code: Select all

Dim array(8) As Byte
Dim value As array(0).AsUInteger
value = &H01020304

It was originally intended for fast access to blocks within an array. In the example above, array(0) <= 4, array(1) <= 3 and so on.

There is one caveat though when using 16 bit parts. Word and long word data access must fall on even address values. If the start of a byte array "falls" on an odd address value, the compiler will generate an error, as it cannot move a long word value to an odd address. Promotional modifiers can still be useful and you should not have any difficulty with promoting word types. However, this feature was left in the compiler when Firewing was targeting 8 bit devices. If writing new code for 16 parts, I would personally not use this particular feature.

[Timbo]

Many thanks for that.

Hopefully soon I will get the hang of it all.

My biggest issue will be when I want to start writing modules and understanding what to include.

Cheers....

[David John Barker]

I wouldn't worry about it - just write your code in a normal program block and test. When you have finished:

• Make all declarations, including subroutines, you want other modules or programs to see "public"
• Make all declarations, including subroutines, you don't want to be seen "private"
• Add "module <name>" at the top of the module
• Add "end module" at the bottom

That's pretty much it to get started with...