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|
{lib}: let
/*
Converts `number` from a binary number to a decimal one.
The input is indented to be a number composed only of `1`s and `0` (e.g., 10010.)
# Type
binaryToDecimal :: Int -> Int
# Arguments
number
: The sequence of `1`s and `0`s defining a binary number, in little endian.
# Examples
binaryToDecimal 1001
=> 9
*/
binaryToDecimal = number: let
binaryList =
builtins.map lib.strings.toInt (lib.lists.reverseList (lib.strings.stringToCharacters (builtins.toString number)));
in
builtins.foldl' (acc: num: acc + num) 0
(lib.lists.imap0 (index: elem: elem * (pow 2 index)) binaryList);
/*
Converts `string` to a (probably) unique numerical id.
This is achieved by hashing the string and returning the first six hex-digits
converted to a base 10 number.
# Type
idFromString :: String -> Int
# Arguments
string
: The string to use as seed for the id generation.
# Examples
idFromString "3d-printer"
=> 10365713
*/
idFromString = string: let
inputSeed =
builtins.concatStringsSep ""
(lib.lists.take 6
(lib.strings.stringToCharacters (builtins.hashString "sha256" string)));
in
lib.trivial.fromHexString inputSeed;
/*
source: https://github.com/NixOS/nix/issues/10387#issuecomment-2494597690
Raises the `base` to the power of `power`.
Considering the small input size and the lack of a built-in power function [2],
this naive power implementation should satisfy reasonable performance
requirements.
Due to the lack of a modulo and bitwise AND operator, it is questionable whether
the recursive exponentiation by squaring [1] implementation would even be
faster.
[1]: https://en.wikipedia.org/wiki/Exponentiation_by_squaring
[2]: https://github.com/NixOS/nix/issues/10387
# Type
pow :: Number -> Number -> Number
# Arguments
base
: The base number to be raised.
power
: The exponent to raise `base` to.
# Examples
pow 2 5
=> 32
*/
pow = base: power:
if power == 0
then 1
else if power > 0
then (base * (pow base (power - 1)))
else builtins.throw "Negative powers are not supported";
in {
inherit binaryToDecimal idFromString pow;
}
|
