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Merge branch 'composeExtensions'

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This commit is contained in:
Shea Levy 2017-04-11 11:16:29 -04:00
commit 52f998a2ce
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lib/trivial.nix
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@ -80,6 +80,15 @@ rec {
# argument, but it's nice this way if several uses of `extends` are cascaded.
extends = f: rattrs: self: let super = rattrs self; in super // f self super;
# Compose two extending functions of the type expected by 'extends'
# into one where changes made in the first are available in the
# 'super' of the second
composeExtensions =
f: g: self: super:
let fApplied = f self super;
super' = super // fApplied;
in fApplied // g self super';
# Create an overridable, recursive attribute set. For example:
#
# nix-repl> obj = makeExtensible (self: { })