Optimize arity wrapper for << and >> #1145
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Prior to this, << (and similarly >>) would be compiled to
var $elm$core$Basics$composeL = F3(function (g, f, x) { ... })
which doesn't match the call sites, which is always of the shape
A2($elm$core$Basics$composeL, f, g)
This change makes it so that composeL/composeR are now wrapped with A2, which improves the performance by about 30%.
Here is the benchmark that I have been using: https://github.com/jfmengels/elm-benchmarks/blob/master/src/WhatIsFaster/FunctionComposition.elm (where I compare
>>
and lambdas)Prior to the change:
After the change:
A further improvement to this (not in this PR, and more in the scope of the compiler would be to replacing
A2(composeL, f, g)
bycomposeL(f, g)
:PS: At some point in the past, the Elm compiler turned composition into lambdas, but it removed that in elm/compiler@6ae0168.