lib: add the toHex and toBase utility functions

`toHex` converts the given positive integer to a string of the hexadecimal
representation of that integer. For example:

```
toHex 0 => "0"

toHex 16 => "10"

toHex 250 => "FA"
```

`toBase base i` converts the positive integer `i` to a list of it
digits in the given `base`. For example:

```
toBase 10 123 => [ 1 2 3 ]

toBase 2 6 => [ 1 1 0 ]

toBase 16 250 => [ 15 10 ]
```
This commit is contained in:
Bas van Dijk 2020-04-20 12:00:23 +02:00
parent d0c12dc612
commit 00022fbeda
3 changed files with 62 additions and 1 deletions

View file

@ -67,7 +67,7 @@ let
inherit (trivial) id const pipe concat or and bitAnd bitOr bitXor
bitNot boolToString mergeAttrs flip mapNullable inNixShell min max
importJSON warn info showWarnings nixpkgsVersion version mod compare
splitByAndCompare functionArgs setFunctionArgs isFunction;
splitByAndCompare functionArgs setFunctionArgs isFunction toHex toBase;
inherit (fixedPoints) fix fix' converge extends composeExtensions
makeExtensible makeExtensibleWithCustomName;
inherit (attrsets) attrByPath hasAttrByPath setAttrByPath

View file

@ -102,6 +102,16 @@ runTests {
expected = 9;
};
testToHex = {
expr = toHex 250;
expected = "FA";
};
testToBase = {
expr = toBase 2 6;
expected = [ 1 1 0 ];
};
# STRINGS
testConcatMapStrings = {

View file

@ -332,4 +332,55 @@ rec {
*/
isFunction = f: builtins.isFunction f ||
(f ? __functor && isFunction (f.__functor f));
/* Convert the given positive integer to a string of its hexadecimal
representation. For example:
toHex 0 => "0"
toHex 16 => "10"
toHex 250 => "FA"
*/
toHex = i:
let
toHexDigit = d:
if d < 10
then toString d
else
{
"10" = "A";
"11" = "B";
"12" = "C";
"13" = "D";
"14" = "E";
"15" = "F";
}.${toString d};
in
lib.concatMapStrings toHexDigit (toBase 16 i);
/* `toBase base i` converts the positive integer i to a list of its
digits in the given base. For example:
toBase 10 123 => [ 1 2 3 ]
toBase 2 6 => [ 1 1 0 ]
toBase 16 250 => [ 15 10 ]
*/
toBase = base: i:
let
go = i:
if i < base
then [i]
else
let
r = i - ((i / base) * base);
q = (i - r) / base;
in
[r] ++ go q;
in
assert (base >= 2);
assert (i >= 0);
lib.reverseList (go i);
}