Function name with Type constraining

New to Julia
1

I met code as follow, anyone can give an syntactic explanation?

mutable struct WriteClosure{T, KW}
    buf::T
end
function (f::WriteClosure)(i, nm, TT, v; kw...)
end
2

If an object of type WriteClosure is called, then that function is called.

Example:

> wc = WriteClosure{T1, T2}(buf)
> wc(i, nm, TT, v) # calling the defined function
3 Likes
3

Thanks!
Well, is it a common syntax, and what’s the name ?

4

The relevant part of the Julia docs is here.
I’d say they are a commonly used feature of the language. Sometimes, they are referred to as “Functor” or “callable struct.”

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5

Method dispatch does not treat function-like objects differently from typical functions. Say in the call foo(a, b), the dispatch is occurring over the types of the callable and the arguments (foo, a, b) isa Tuple{typeof(foo), typeof(a), typeof(b)}. In fact, you can add methods to foo with the same syntax (::typeof(foo))(c) = "blah", but typical functions are conveniently given a const name and extra behaviors via subtyping Function. If the struct type isn’t singleton (has no fields), then you can’t give any of its instances a const name, but otherwise you could opt into much of function’s behaviors.

1 Like
6

Thanks!
I should read the docs more often.