diff options
Diffstat (limited to 'lib/trivial.nix')
| -rw-r--r-- | lib/trivial.nix | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/lib/trivial.nix b/lib/trivial.nix index 3e606f0df48f3..a0c31757ba7ae 100644 --- a/lib/trivial.nix +++ b/lib/trivial.nix @@ -53,6 +53,27 @@ 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; + # Create an overridable, recursive attribute set. For example: + # + # nix-repl> obj = makeExtensible (self: { }) + # + # nix-repl> obj + # { __unfix__ = «lambda»; extend = «lambda»; } + # + # nix-repl> obj = obj.extend (self: super: { foo = "foo"; }) + # + # nix-repl> obj + # { __unfix__ = «lambda»; extend = «lambda»; foo = "foo"; } + # + # nix-repl> obj = obj.extend (self: super: { foo = super.foo + " + "; bar = "bar"; foobar = self.foo + self.bar; }) + # + # nix-repl> obj + # { __unfix__ = «lambda»; bar = "bar"; extend = «lambda»; foo = "foo + "; foobar = "foo + bar"; } + makeExtensible = rattrs: + fix' rattrs // { + extend = f: makeExtensible (extends f rattrs); + }; + # Flip the order of the arguments of a binary function. flip = f: a: b: f b a; |