[Harrison Pratt]

The code below causes a fatal error in the last line of clause:

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class predicates
    colorToBinary : (gdiplus_native::color Color) -> binary Binary. % a 4 byte binary within custom color binary
clauses
    colorToBinary(Color) = Binary :-
        R = Color:gdiplus::redPart(), % unsigned8
        G = Color:gdiplus::greenPart(),
        B = Color:gdiplus::bluePart(),
        A = Color:gdiplus::alphaPart(),
        Binary = binary::createAtomic(4),
        binary::setBinary(Binary, 0, $[R]),
        binary::setBinary(Binary, 1, $[G]),
        binary::setBinary(Binary, 2, $[B]),
        binary::setBinary(Binary, 3, $[A]). % fatal error c098 : Illegal binary element 'A'

But if I change the last few lines to this, it compiles without complaint!

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        ...
        binary::setBinary(Binary, 2, $[B]),
        binary::setBinary(Binary, 3, $[A]),
        succeed.

Am I not understanding something basic or is it a compiler quirk?

[Thomas Linder Puls]

It is clearly a bug in the compiler.

Regarding the code. It "nags" me that you create binaries (e.g. $[R]) just to set an unsigned8 in a binary.

I suggest you use setIndexed_unsigned8 this instead:

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        Binary = binary::createAtomic(4),
        binary::setIndexed_unsigned8(Binary, 0, R),
        binary::setIndexed_unsigned8(Binary, 1, G),
        binary::setIndexed_unsigned8(Binary, 2, B),
        binary::setIndexed_unsigned8(Binary, 3, A).

Or perhaps (a matter of taste):

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        Color2 = A << 24 ++ B << 16 ++ G << 8 ++ R, % 0x_AA_BB_GG_RR
        Binary = binary::createAtomic(4),
        binary::setIndexed_unsigned(Binary, 0, Color2).

[Thomas Linder Puls]

By the way if you need to create (larger) binaries in a specific format then I can suggest this approach:

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        S = outputStream_binary::new(),
        S:write(hasDomain(unsigned8, R)),
        S:write(hasDomain(unsigned8, G)),
        S:write(hasDomain(unsigned8, B)),
        S:write(hasDomain(unsigned8, A)),
        Binary = S:getBinary().

The usage of hasDomain is not necessary here, because the values have the correct type. But in more complex cases it is a good safety precaution to explicitly state the type you want to write.

[Harrison Pratt]

Thank you very much for the tips on working with binary structures, Thomas!
I have not worked with binaries before ... and it shows.