promotion change?: promote(Int,Float32) = Float32

[StefanKarpinski]

Spurred by this discussion we should consider allowing Float32 computations to "persist" more easily in the presence of Int values.

[JeffBezanson]

I have also thought that operations on Float32 arrays should more readily keep the Float32 type, for example Matrix{Float32}+Float64 should probably give a Float32 matrix for space reasons.

[StefanKarpinski]

Seems like a good idea to me.

[staticfloat]

This seems in line with most of the rest of Julia's philosophy regarding types, I must say I myself have been guilty of writing code such as Gunnar's function definition, and this seems more natural.

I'm not sure sure about Matrix{Float32} + Float64 yielding Float32 though, because Float32 + Float64 yields Float64. Having matrices with different promotion rules from the elementary types they are defined on seems deceptive.

[StefanKarpinski]

We already do that though:

julia> v = Int8[1,2,3]
3-element Int8 Array:
 1
 2
 3

julia> v + v
3-element Int8 Array:
 2
 4
 6

This gave me pause at first, but it's really the behavior you want for arrays because you definitely don't want to blow up memory by accident when you're working with them. We should make it a consistent policy.

[staticfloat]

Excellent counter-example; I agree what you propose seems like the "best" way to handle this consistently.