Calling member functions like C++

[L4stR1t3s]

From https://github.com/carbon-language/carbon-lang/blob/trunk/docs/design/classes.md#methods:

Methods are called using the dot . member syntax, c.Diameter() and c.Expand(...).

I suggest also allowing calling methods like this: Diameter(c) and Expand(c, ...), like some C++ STL functions.

begin(), end(), size(), empty(), ... are defined in the STL to access them like begin(vec) for example. begin() and end() for example also have implementations for C style arrays. This means it is possible to write generic code that works for both STL containers and C style arrays.

If Carbon made member functions by default available as func(object), there would be no need to define template functions to access member functions, if you want to do this.

This can especially come in handy when writing templated code:

void print(int x) { ... }
struct Object {
    void print() { ... }
}
template <typename T>
void func(T x) {
    ...
    print(x);
    ...
}

[geoffromer]

I'm fairly sure C++ doesn't allow calling member functions that way, so I'd suggest changing the issue title to something like "Calling member functions as free functions".

I think adapters already address the template use case for this feature in a more general way.

[L4stR1t3s]

I'm fairly sure C++ doesn't allow calling member functions that way, so I'd suggest changing the issue title to something like "Calling member functions as free functions".

Uh, right. Was writing this, and then was called away and when I came back I assumed I had already written more than I apparently had...

I forgot to mention that the C++ STL offers a whole range of template functions to call common member functions like begin(), end(), empty(), size(), ... so you can use them like func(object). begin() and end() for example also have an implementation for C style arrays, meaning you can write generic code that loops over STL containers as well as C style arrays.

I was thinking that this could be a generic feature for Carbon.

I will update the initial post.

[geoffromer]

I forgot to mention that the C++ STL offers a whole range of template functions to call common member functions like begin(), end(), empty(), size(), ... so you can use them like func(object). begin() and end() for example also have an implementation for C style arrays, meaning you can write generic code that loops over STL containers as well as C style arrays.

The C++ standard library has to do this to work around limitations of C++ that don't apply to Carbon. C style arrays are not library types or class types, so they can't be extended to support method calls. In Carbon, our intent is that all object types (including array types) are library types, so for example, if container iteration in Carbon is defined in terms of Begin and End methods, we can define those methods on the array type. So it seems like this feature would be much less useful in Carbon than in C++.

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