Hi, is there any other function composition operators except -> ?

For example, I’m looking for >> operator (like in F#)

Could you please provide more function composition examples?

Thnaks a lot!

Hi, is there any other function composition operators except -> ?

For example, I’m looking for >> operator (like in F#)

Could you please provide more function composition examples?

Thnaks a lot!

4 Likes

There’s no function composition operator in rescript.

You can define your own if you use legacy syntax but custom infix ops are not supported by rescript.

this is reason syntax for example:

`let (>>) = (f,g,x) => g(f(x));`

note that there’s a runtime cost when you use this. I think it’s better to stick with `->`

which is a syntax transform.

2 Likes

Thanks for clarification!

Wasn’t a subset of infix operators going to be supported? If so, `>>`

is a pretty common one so maybe it will be included.

2 Likes

The cost comes from the composition of high order function and curried by default – (the compiler can not infer the arity of `f`

, `g`

since we don’t see the source).

If you use uncurried style, the cost is affordable.

```
let (>>) = (. f,g,x) => g(. f(. x));
```

This doesn’t seem to work:

```
let succ2 = succ >> succ;
```

Error:

```
This is an uncurried BuckleScript function. It must be applied with a dot.
Like this: foo(. a, b)
Not like this: foo(a, b)
```

But admittedly I’m checking in the Reason Playground. Perhaps this has been fixed in the latest ReScript?

indeed. the closet thing is

```
let (>>) = ( f,g,x) => g(. f(. x));
let u = ((.x)=> x+1)>>((.x)=>x + 1);
```