diff options
Diffstat (limited to 'lib')
| -rw-r--r-- | lib/attrsets.nix | 9 | ||||
| -rw-r--r-- | lib/default.nix | 4 | ||||
| -rw-r--r-- | lib/fixed-points.nix | 10 |
3 files changed, 21 insertions, 2 deletions
diff --git a/lib/attrsets.nix b/lib/attrsets.nix index 2a1b866dbc5..d374d229f59 100644 --- a/lib/attrsets.nix +++ b/lib/attrsets.nix @@ -94,6 +94,15 @@ rec { attrValues = builtins.attrValues or (attrs: attrVals (attrNames attrs) attrs); + /* Given a set of attribute names, return the set of the corresponding + attributes from the given set. + + Example: + getAttrs [ "a" "b" ] { a = 1; b = 2; c = 3; } + => { a = 1; b = 2; } + */ + getAttrs = names: attrs: genAttrs names (name: attrs.${name}); + /* Collect each attribute named `attr' from a list of attribute sets. Sets that don't contain the named attribute are ignored. diff --git a/lib/default.nix b/lib/default.nix index d7a05fec833..e4e3e7d325a 100644 --- a/lib/default.nix +++ b/lib/default.nix @@ -61,10 +61,10 @@ let boolToString mergeAttrs flip mapNullable inNixShell min max importJSON warn info nixpkgsVersion version mod compare splitByAndCompare functionArgs setFunctionArgs isFunction; - inherit (fixedPoints) fix fix' extends composeExtensions + inherit (fixedPoints) fix fix' converge extends composeExtensions makeExtensible makeExtensibleWithCustomName; inherit (attrsets) attrByPath hasAttrByPath setAttrByPath - getAttrFromPath attrVals attrValues catAttrs filterAttrs + getAttrFromPath attrVals attrValues getAttrs catAttrs filterAttrs filterAttrsRecursive foldAttrs collect nameValuePair mapAttrs mapAttrs' mapAttrsToList mapAttrsRecursive mapAttrsRecursiveCond genAttrs isDerivation toDerivation optionalAttrs diff --git a/lib/fixed-points.nix b/lib/fixed-points.nix index 7169c46fcbb..2f818c88de5 100644 --- a/lib/fixed-points.nix +++ b/lib/fixed-points.nix @@ -24,6 +24,16 @@ rec { # for a concrete example. fix' = f: let x = f x // { __unfix__ = f; }; in x; + # Return the fixpoint that `f` converges to when called recursively, starting + # with the input `x`. + # + # nix-repl> converge (x: x / 2) 16 + # 0 + converge = f: x: + if (f x) == x + then x + else converge f (f x); + # Modify the contents of an explicitly recursive attribute set in a way that # honors `self`-references. This is accomplished with a function # |