# package ppx_compose

## Install

## Dune Dependency

## Authors

## Maintainers

## Sources

`sha256=87f063215e9f06d4433302f492fb35c72b25f09737ba748d9df3542f562f9a7f`

`sha512=7c8c14f5b28c5173e74bec8176b59697cc1ec7f48ccbbab4656b083259fde6666b4399a74b13fc3605d50cb48ff4c11ff8b96fafa6ef4af5613eab5ccf5a49f1`

## README.md.html

## README.md

`ppx_compose`

- Inlined Function Composition

`ppx_compose`

is a simple syntax extension which rewrites code containing function compositions into composition-free code, effectively inlining the composition operators. The following two operators are supported

```
let (%) g f x = g (f x)
let (%>) f g x = g (f x)
```

Corresponding definitions are not provided, so partial applications of `(%)`

and `(%>)`

will be undefined unless you provide the definitions.

The following rewrites are done:

A composition occurring to the left of an application is reduced by applying each term of the composition from right to left to the argument, ignoring associative variations.

A composition which is not the left side of an application is first turned into one by η-expansion, then the above rule applies.

Any partially applied composition operators are passed though unchanged.

E.g.

```
h % g % f ==> (fun x -> h (f (g x)))
h % (g % f) ==> (fun x -> h (f (g x)))
(g % f) (h % h) ==> g (f (fun x -> h (h x)))
```

#### Is It Needed?

Recent flambda-enabled compilers can inline the following alternative definitions of the composition operators [1]:

```
let (%) g f = (); fun x -> g (f x)
let (%>) f g = (); fun x -> g (f x)
```

so this syntax extension will likely be retired at some point.