mirror of
https://github.com/NixOS/nixpkgs.git
synced 2024-12-11 07:04:28 +00:00
103 lines
2.5 KiB
Nix
103 lines
2.5 KiB
Nix
{ lib }:
|
|
rec {
|
|
|
|
/* The identity function
|
|
For when you need a function that does “nothing”.
|
|
|
|
Type: id :: a -> a
|
|
*/
|
|
id = x: x;
|
|
|
|
/* The constant function
|
|
Ignores the second argument.
|
|
Or: Construct a function that always returns a static value.
|
|
|
|
Type: const :: a -> b -> a
|
|
Example:
|
|
let f = const 5; in f 10
|
|
=> 5
|
|
*/
|
|
const = x: y: x;
|
|
|
|
|
|
## Named versions corresponding to some builtin operators.
|
|
|
|
/* Concat two strings */
|
|
concat = x: y: x ++ y;
|
|
|
|
/* boolean “or” */
|
|
or = x: y: x || y;
|
|
|
|
/* boolean “and” */
|
|
and = x: y: x && y;
|
|
|
|
/* Convert a boolean to a string.
|
|
Note that toString on a bool returns "1" and "".
|
|
*/
|
|
boolToString = b: if b then "true" else "false";
|
|
|
|
/* Merge two attribute sets shallowly, right side trumps left
|
|
|
|
Example:
|
|
mergeAttrs { a = 1; b = 2; } { b = 3; c = 4; }
|
|
=> { a = 1; b = 3; c = 4; }
|
|
*/
|
|
mergeAttrs = x: y: x // y;
|
|
|
|
# Flip the order of the arguments of a binary function.
|
|
flip = f: a: b: f b a;
|
|
|
|
# Apply function if argument is non-null
|
|
mapNullable = f: a: if isNull a then a else f a;
|
|
|
|
# Pull in some builtins not included elsewhere.
|
|
inherit (builtins)
|
|
pathExists readFile isBool isFunction
|
|
isInt add sub lessThan
|
|
seq deepSeq genericClosure;
|
|
|
|
inherit (lib.strings) fileContents;
|
|
|
|
# Return the Nixpkgs version number.
|
|
nixpkgsVersion =
|
|
let suffixFile = ../.version-suffix; in
|
|
fileContents ../.version
|
|
+ (if pathExists suffixFile then fileContents suffixFile else "pre-git");
|
|
|
|
# Whether we're being called by nix-shell.
|
|
inNixShell = builtins.getEnv "IN_NIX_SHELL" != "";
|
|
|
|
# Return minimum/maximum of two numbers.
|
|
min = x: y: if x < y then x else y;
|
|
max = x: y: if x > y then x else y;
|
|
|
|
/* Integer modulus
|
|
|
|
Example:
|
|
mod 11 10
|
|
=> 1
|
|
mod 1 10
|
|
=> 1
|
|
*/
|
|
mod = base: int: base - (int * (builtins.div base int));
|
|
|
|
/* Reads a JSON file. */
|
|
importJSON = path:
|
|
builtins.fromJSON (builtins.readFile path);
|
|
|
|
/* See https://github.com/NixOS/nix/issues/749. Eventually we'd like these
|
|
to expand to Nix builtins that carry metadata so that Nix can filter out
|
|
the INFO messages without parsing the message string.
|
|
|
|
Usage:
|
|
{
|
|
foo = lib.warn "foo is deprecated" oldFoo;
|
|
}
|
|
|
|
TODO: figure out a clever way to integrate location information from
|
|
something like __unsafeGetAttrPos.
|
|
*/
|
|
warn = msg: builtins.trace "WARNING: ${msg}";
|
|
info = msg: builtins.trace "INFO: ${msg}";
|
|
}
|