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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";
}
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