Is it possible to dispatch on the arity of a function?

[xiaodai]

Say I want to dispatch fn(gn::Function) base on the arity of gn. Is it possible?

[pablosanjose]

Check out this thread

Finding the number of arguments of an anonymous function

I have an API wherein a kwarg is a function. function apifunc(; f::Function = identity) ... end I would like to do something different depending on the number of arguments of f, so that apifunc(f = x -> 2) calls _apifunc1(f) but apifunc(f = (x,y) -> 2) calls _apifunc2(f). Is there a way to achieve that, preferably in a non-dynamical way? In other words, is there any way to do introspection on the allowed signatures of a function’s methods?

TL;DR: isapplicable applicable is probably your best approach for this

[giordano]

Methods are not first-class citizens in Julia, so you can’t directly dispatch on the signature of a function. Using isapplicabile in the body of the function is an option, FunctionWrappers.jl is also often recommended in these cases, depending on what you exactly want to achieve

[chakravala]

@pablosanjose

TL;DR: isapplicable is probably your best approach for this

That is incorrect, according to the thread it is applicable instead of isapplicable:

@pfitzseb

FWIW, applicable seems to fare fairly well and should be safe:

[pablosanjose]

Yep, my bad