b53ef57554
* Added a function mapAttrsRecursive, which is like mapAttrs, but recursively applies itself to attribute sets. * Commented and cleaned up some functions. svn path=/nixpkgs/trunk/; revision=14495
102 lines
3 KiB
Nix
102 lines
3 KiB
Nix
# Operations on attribute sets.
|
|
|
|
with {
|
|
inherit (builtins) head tail;
|
|
inherit (import ./default.nix) fold;
|
|
inherit (import ./strings.nix) concatStringsSep;
|
|
};
|
|
|
|
rec {
|
|
inherit (builtins) attrNames listToAttrs hasAttr isAttrs;
|
|
|
|
|
|
/* Return an attribute from nested attribute sets. For instance
|
|
["x" "y"] applied to some set e returns e.x.y, if it exists. The
|
|
default value is returned otherwise. !!! there is also
|
|
builtins.getAttr (is there a better name for this function?)
|
|
*/
|
|
getAttr = attrPath: default: e:
|
|
let attr = head attrPath;
|
|
in
|
|
if attrPath == [] then e
|
|
else if builtins ? hasAttr && hasAttr attr e
|
|
then getAttr (tail attrPath) default (builtins.getAttr attr e)
|
|
else default;
|
|
|
|
|
|
getAttrFromPath = attrPath: set:
|
|
let errorMsg = "cannot find attribute `" + concatStringsSep "." attrPath + "'";
|
|
in getAttr attrPath (abort errorMsg) set;
|
|
|
|
|
|
/* Return the specified attributes from a set.
|
|
|
|
Example:
|
|
attrVals ["a" "b" "c"] as
|
|
=> [as.a as.b as.c]
|
|
*/
|
|
attrVals = nameList: set:
|
|
map (x: builtins.getAttr x set) nameList;
|
|
|
|
|
|
/* Return the values of all attributes in the given set, sorted by
|
|
attribute name.
|
|
|
|
Example:
|
|
attrValues {c = 3; a = 1; b = 2;}
|
|
=> [1 2 3]
|
|
*/
|
|
attrValues = attrs: attrVals (attrNames attrs) attrs;
|
|
|
|
|
|
/* Collect each attribute named `attr' from a list of attribute
|
|
sets. Sets that don't contain the named attribute are ignored.
|
|
|
|
Example:
|
|
catAttrs "a" [{a = 1;} {b = 0;} {a = 2;}]
|
|
=> [1 2]
|
|
*/
|
|
catAttrs = attr: l: fold (s: l: if hasAttr attr s then [(builtins.getAttr attr s)] ++ l else l) [] l;
|
|
|
|
|
|
/* Utility function that creates a {name, value} pair as expected by
|
|
builtins.listToAttrs. */
|
|
nameValuePair = name: value: { inherit name value; };
|
|
|
|
|
|
/* Apply a function to each element in an attribute set. The
|
|
function takes two arguments --- the attribute name and its value
|
|
--- and returns the new value for the attribute. The result is a
|
|
new attribute set.
|
|
|
|
Example:
|
|
mapAttrs (name: value: name + "-" + value)
|
|
{x = "foo"; y = "bar";}
|
|
=> {x = "x-foo"; y = "y-bar";}
|
|
*/
|
|
mapAttrs = f: set:
|
|
listToAttrs (map (attr: nameValuePair attr (f attr (builtins.getAttr attr set))) (attrNames set));
|
|
|
|
|
|
/* Like `mapAttrs', except that it recursively applies itself to
|
|
values that attribute sets. Also, the first argument is a *list*
|
|
of the names of the containing attributes.
|
|
|
|
Example:
|
|
mapAttrsRecursive (path: value: concatStringsSep "-" (path ++ [value]))
|
|
{ n = { a = "A"; m = { b = "B"; c = "C"; }; }; d = "D"; }
|
|
=> { n = { a = "n-a-A"; m = { b = "n-m-b-B"; c = "n-m-c-C"; }; }; d = "d-D"; }
|
|
*/
|
|
mapAttrsRecursive =
|
|
let
|
|
recurse = path: f: set:
|
|
let
|
|
g =
|
|
name: value:
|
|
if isAttrs value
|
|
then recurse (path ++ [name]) f value
|
|
else f (path ++ [name]) value;
|
|
in mapAttrs g set;
|
|
in recurse [];
|
|
|
|
}
|