mirror of
https://github.com/NixOS/nixpkgs.git
synced 2024-11-30 09:31:01 +00:00
4a91cfd32b
This is primarily useful in Nix expressions that are also intended to be used by nix-shell. It allows saying things like: buildInputs = [ ... ] ++ (if inNixShell then [ emacs ] else [ ]); This should not be used in Nixpkgs (since the question of what constitutes a useful nix-shell environment is very subjective).
54 lines
1.4 KiB
Nix
54 lines
1.4 KiB
Nix
with {
|
|
inherit (import ./lists.nix) deepSeqList;
|
|
inherit (import ./attrsets.nix) deepSeqAttrs;
|
|
};
|
|
|
|
rec {
|
|
|
|
# Identity function.
|
|
id = x: x;
|
|
|
|
# Constant function.
|
|
const = x: y: x;
|
|
|
|
# Named versions corresponding to some builtin operators.
|
|
concat = x: y: x ++ y;
|
|
or = x: y: x || y;
|
|
and = x: y: x && y;
|
|
mergeAttrs = x: y: x // y;
|
|
|
|
# Take a function and evaluate it with its own returned value.
|
|
fix = f: let result = f result; in result;
|
|
|
|
# Flip the order of the arguments of a binary function.
|
|
flip = f: a: b: f b a;
|
|
|
|
# `seq x y' evaluates x, then returns y. That is, it forces strict
|
|
# evaluation of its first argument.
|
|
seq = x: y: if x == null then y else y;
|
|
|
|
# Like `seq', but recurses into lists and attribute sets to force evaluation
|
|
# of all list elements/attributes.
|
|
deepSeq = x: y:
|
|
if builtins.isList x
|
|
then deepSeqList x y
|
|
else if builtins.isAttrs x
|
|
then deepSeqAttrs x y
|
|
else seq x y;
|
|
|
|
# Pull in some builtins not included elsewhere.
|
|
inherit (builtins)
|
|
pathExists readFile isBool isFunction
|
|
isInt add sub lessThan;
|
|
|
|
# Return the Nixpkgs version number.
|
|
nixpkgsVersion =
|
|
let suffixFile = ../.version-suffix; in
|
|
readFile ../.version
|
|
+ (if pathExists suffixFile then readFile suffixFile else "pre-git");
|
|
|
|
# Whether we're being called by nix-shell. This is useful to
|
|
inNixShell = builtins.getEnv "IN_NIX_SHELL" == "1";
|
|
|
|
}
|