ppx_compose
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.
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