Given a function and some argument types, it should be possible to know the return type without actually running the executing the method. How can I do that? Is there something like a functiontype(f,argtypes)? My goal is to be able to promote the type, given multiple functions and arguments as tupl…

In 0.6, you might want julia> Base.return_types(cos, Tuple{Float64}) 1-element Array{Any,1}: Float64 edit: Note that this is afaik intended for use in @generated functions, and not terribly fast for runtime use.

No it cannot be used in generated functions. It’s also not intended for use in what the OP wants. It’s there only for empty comprehensions.

What would be the recommended way of getting the type of a function’s output then? I am trying to allocate an array, and since values from those functions will get added up in there, I need to allocate the correct type to begin with.

[image] jebej: I am trying to allocate an array, and since values from those functions will get added up in there, I need to allocate the correct type to begin with. If you can, use something like map or a generator/comprehension or broadcast (or a dot call), since those functions will take c…

I’m confused as to why this is complicated: isn’t the return typed determined by inference at compile time? Assuming that the function is type-stable of course…

The reason is that inference isn’t part of the language, it’s part of the implementation. Consequently, as the implementation improves, it may also improve inference, changing the results. For example, suppose that you have a method which returns Union{Int64, Nothing}, but then version 1.1 of Julia…

[image] jebej: Assuming that the function is type-stable of course That’s precisely the rub. Not only could inference be disabled, but collecting things like: f() = rand() > 1 ? 1 : 1.0 [f() for _ in 1:3] used to return an Vector{Any} (a long long time ago). We’ve made inference better, s…

Obtaining a function's output type

General Usage

mbauman June 1, 2018, 6:33pm 6

Hah, we have the same thread going on over in #dev: Promote_op and preallocating result of linear operators - #4 by mbauman

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Obtaining a function's output type

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