> abstract typeA
>
> immutable typeA1 <: typeA end
> immutable typeA2 <: typeA end
>
> type typeB1 end
> type typeB2 end
More Julian would be to write:
transformType(T::Type{typeA1}) = typeB1
transformType(T::Type{typeA2}) = typeB2
transformType(T::Type) = error("Cannot handle type $T")
> function transformType(T)
> if T == typeA1
> return typeB1
> elseif T == typeA2
> return typeB2
> end
> error("Cannot handle type $T")
> end
>
> function compute{T<:typeA}(a::transformType(T), b::transformType(T))
> return (a, b)
> end
>
> but it failed with the following error message
>
> ERROR: Cannot handle type T<:typeA
> in error at error.jl:21
> in transformType at /Users/bpiwowar/Desktop/test.jl:15
> in include at
> /opt/homebrew-cask/Caskroom/julia/0.3.5/Julia-0.3.5.app/Contents/Resources/julia/lib/julia/sys.dylib
> in include_from_node1 at loading.jl:128
> in process_options at
> /opt/homebrew-cask/Caskroom/julia/0.3.5/Julia-0.3.5.app/Contents/Resources/julia/lib/julia/sys.dylib
> in _start at
> /opt/homebrew-cask/Caskroom/julia/0.3.5/Julia-0.3.5.app/Contents/Resources/julia/lib/julia/sys.dylib
> while loading /Users/bpiwowar/Desktop/test.jl, in expression starting on
> line 18
>
> The type transformType(T)is hence computed when the method is defined, but
> not when the method is called. Is there any way to prevent this (to defer
> evaluation at compilation time?).
Have a look at stagedfunction (v0.4).
> The only other way (I can think of) to get this result would be to use
> macros and enumerate the different possible types, but if somebody can
> think of a better solution, thanks!
why not write:
type typeB1 <: typeB end
type typeB2 <: typeB end
compute(a::typeB, b::typeB) = return (a, b)
