Why Val{...}?

[e3c6]

Why is Val{..} needed? Shouldn’t constant propagation make Val obsolete (https://github.com/JuliaLang/julia/pull/24362)?

[kristoffer.carlsson]

Val forces specialization which can sometimes be desired.

[StefanKarpinski]

Val also predates that kind of contant propagation.

[kristoffer.carlsson]

@StefanKarpinski

Val also predates that kind of contant propagation.

Sure, my point was just that even now, there are reasons why it is still useful.

[e3c6]

Is there an example, where constant propagation is not enough?

[kristoffer.carlsson]

@e3c6

Is there an example, where constant propagation is not enough?

You might not only want to specialize on constants.

Getproperty, decorations, inheritance in 0.7

How about if I want to dynamically specialise on a certain value? using StaticArrays function f(n::Int) b = rand(SVector{n}) for i in 1:10000 b += rand(SVector{n}) end return b end function f(_n::Val{n}) where n b = rand(SVector{n}) for i in 1:10000 b += rand(SVector{n}) end return b end g1() = f(rand(4:4)) g2() = f(Val(rand(4:4))) @time g1() @time g2() julia> @time g1(); 0.015060 seconds (140.02 k allocations: 8.851 MiB) julia> @time g2(…