# package ppx_compose

## Install

## Dune Dependency

## Authors

## Maintainers

## Sources

`sha256=414f72a7659f2e85cf87ddcbf9981f793aa78ea3a607c35a8237e5ee305811b3`

`sha512=d69bfab88b4d4949bc5189724f954f33e1c2fa36d9fcf1dded351d379c241345533bf12bf493b26acbbcb6bd726674c22c934f037ec0b2820b6a5f99cfbc9ba3`

## 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.