diff options
Diffstat (limited to 'pkgs/lib/default.nix')
| -rw-r--r-- | pkgs/lib/default.nix | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/pkgs/lib/default.nix b/pkgs/lib/default.nix index 829f8e52a208..da279302306f 100644 --- a/pkgs/lib/default.nix +++ b/pkgs/lib/default.nix @@ -61,6 +61,16 @@ rec { fold (x: y: if pred x then [x] ++ y else y) [] list; + # Find the sole element in the list matching the specified + # predicate, or returns the default value. + findSingle = pred: default: list: + let found = filter pred list; + in if found == [] then default + else if tail found != [] then + abort "Multiple elements match predicate in findSingle." + else head found; + + # Return true if each element of a list is equal, false otherwise. eqLists = xs: ys: if xs == [] && ys == [] then true |