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|
{ lib }:
let
zipIntBits = f: x: y:
let
# (intToBits 6) -> [ 0 1 1 ]
intToBits = x:
if x==0 then
[]
else
let
headbit = if (x / 2) * 2 != x then 1 else 0; # x & 1
tailbits = if x < 0 then 9223372036854775807 + ((x+1) / 2) else x / 2; # x >>> 1
in
[headbit] ++ (intToBits tailbits);
# (bitsToInt [ 0 1 1 ]) -> 6
bitsToInt = l:
if l==[] then
0
else
(builtins.head l) + (2 * (bitsToInt (builtins.tail l)));
zipListsWith' = fst: snd:
if fst==[] && snd==[] then
[]
else if fst==[] then
[(f 0 (builtins.head snd))] ++ (zipListsWith' [] (builtins.tail snd))
else if snd==[] then
[(f (builtins.head fst) 0 )] ++ (zipListsWith' (builtins.tail fst) [] )
else
[(f (builtins.head fst) (builtins.head snd))] ++ (zipListsWith' (builtins.tail fst) (builtins.tail snd));
in
assert (builtins.isInt x) && (builtins.isInt y);
bitsToInt (zipListsWith' (intToBits x) (intToBits y));
in
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;
/* bitwise “and” */
bitAnd = builtins.bitAnd or zipIntBits (a: b: if a==1 && b==1 then 1 else 0);
/* bitwise “or” */
bitOr = builtins.bitOr or zipIntBits (a: b: if a==1 || b==1 then 1 else 0);
/* bitwise “xor” */
bitXor = builtins.bitXor or zipIntBits (a: b: if a!=b then 1 else 0);
/* 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
isInt add sub lessThan
seq deepSeq genericClosure;
inherit (lib.strings) fileContents;
release = fileContents ../.version;
versionSuffix = let suffixFile = ../.version-suffix; in
if pathExists suffixFile then fileContents suffixFile else "pre-git";
# Return the Nixpkgs version number.
version = release + versionSuffix;
nixpkgsVersion = builtins.trace "`lib.nixpkgsVersion` is deprecated, use `lib.version` instead!" version;
# 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));
/* C-style comparisons
a < b, compare a b => -1
a == b, compare a b => 0
a > b, compare a b => 1
*/
compare = a: b:
if a < b
then -1
else if a > b
then 1
else 0;
/* Split type into two subtypes by predicate `p`, take all elements
of the first subtype to be less than all the elements of the
second subtype, compare elements of a single subtype with `yes`
and `no` respectively.
Example:
let cmp = splitByAndCompare (hasPrefix "foo") compare compare; in
cmp "a" "z" => -1
cmp "fooa" "fooz" => -1
cmp "f" "a" => 1
cmp "fooa" "a" => -1
# while
compare "fooa" "a" => 1
*/
splitByAndCompare = p: yes: no: a: b:
if p a
then if p b then yes a b else -1
else if p b then 1 else no a b;
/* 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}";
# | Add metadata about expected function arguments to a function.
# The metadata should match the format given by
# builtins.functionArgs, i.e. a set from expected argument to a bool
# representing whether that argument has a default or not.
# setFunctionArgs : (a → b) → Map String Bool → (a → b)
#
# This function is necessary because you can't dynamically create a
# function of the { a, b ? foo, ... }: format, but some facilities
# like callPackage expect to be able to query expected arguments.
setFunctionArgs = f: args:
{ # TODO: Should we add call-time "type" checking like built in?
__functor = self: f;
__functionArgs = args;
};
# | Extract the expected function arguments from a function.
# This works both with nix-native { a, b ? foo, ... }: style
# functions and functions with args set with 'setFunctionArgs'. It
# has the same return type and semantics as builtins.functionArgs.
# setFunctionArgs : (a → b) → Map String Bool.
functionArgs = f: f.__functionArgs or (builtins.functionArgs f);
isFunction = f: builtins.isFunction f ||
(f ? __functor && isFunction (f.__functor f));
}
|