Specific function type

New to Julia
2

I don’t think you can generally get more specific than Function by default, because the output type and implementation of a function can depend on its input values. However, you can use callable structs to essentially append metadata to a function.

Example:

struct FunctionWrapper
  input_types::Vector{DataType}
  output_type::DataType
  f::Function
end

# Callable struct syntax
function (fw::FunctionWrapper)(args...)
  @assert all(isa.(args, fw.input_types)) 
  output = fw.f(args...)
  @assert output isa fw.output_type
  return output
end

foo(x::Int) = x + 1
foo2 = FunctionWrapper([Int], Int, foo)

julia> foo2(5)
6

julia> foo2(5.0)
ERROR: AssertionError: all(isa.(args, fw.input_types))

This is obviously a lot of extra code so you would only do it in a few cases where you really needed that extra metadata.

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