why `->` before return type about mun HOT 2 CLOSED

Having a symbol at all is for consistency. We want a symbol to associate a type to a construct. We use : to ascribe a binding (let x:int: x is of type int) and -> to denote a return type (fn f(int) -> int applying f to an int results in an int).

The -> is used to distinguish the return type from the rest of the signature. We used to have : but we choose to revert to the same as Rust (partly because it was confusing for users coming from Rust).

There are a lot of languages that use -> (Mathematics, Rust, Swift, C++, Python) and there are a lot of languages using : (Typescript, Scala, Perl), there is no silver bullet. Here is a more formal explanation, which I think is also the reason Rust is using the return arrow. There are basically two cases where the return arrow makes an appearance:

1. Function item declaration: fn foo(x: int) -> int {}
2. Assignment of a function to a variable with explicit type: let x : fn(int) -> int = foo (not implemented yet)

One might say the arrow is clearer in the case where a function type is specified. To me let x : fn(T) -> U; is easier to understand than let x : fn(T) : U; but you may disagree.

All in all, I think its a matter of preference, we choose to use the return arrow.

from mun.

@baszalmstra i am not asking to use : . i am proposing not having a symbol at all. like Go or Zig.

from mun.