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lib: bitAnd, bitOr, bitXor (bitsize-agnostic fallback function) (#41491)

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* lib: bitAnd, bitOr, bitXor

* lib: test for bitAnd, bitOr, bitXor

* lib: bitsize-agnostic zipIntBits

* lib: bitNot

* lib: bitNot
This commit is contained in:
volth 2018-06-10 19:25:48 +00:00 committed by xeji
parent e544e4f564
commit 3c2bbe217c
3 changed files with 68 additions and 4 deletions
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8
lib/default.nix
View File

@ -56,10 +56,10 @@ let
hasAttr head isAttrs isBool isInt isList isString length
lessThan listToAttrs pathExists readFile replaceStrings seq
stringLength sub substring tail;
inherit (trivial) id const concat or and boolToString mergeAttrs
flip mapNullable inNixShell min max importJSON warn info
nixpkgsVersion version mod compare splitByAndCompare
functionArgs setFunctionArgs isFunction;
inherit (trivial) id const concat or and bitAnd bitOr bitXor bitNot
boolToString mergeAttrs flip mapNullable inNixShell min max
importJSON warn info nixpkgsVersion version mod compare
splitByAndCompare functionArgs setFunctionArgs isFunction;
inherit (fixedPoints) fix fix' extends composeExtensions
makeExtensible makeExtensibleWithCustomName;

15
lib/tests/misc.nix
View File

@ -45,6 +45,21 @@ runTests {
expected = true;
};
testBitAnd = {
expr = (bitAnd 3 10);
expected = 2;
};
testBitOr = {
expr = (bitOr 3 10);
expected = 11;
};
testBitXor = {
expr = (bitXor 3 10);
expected = 9;
};
# STRINGS
testConcatMapStrings = {

49
lib/trivial.nix
View File

@ -1,4 +1,41 @@
{ lib }:
let
zipIntBits = f: x: y:
let
# (intToBits 6) -> [ 0 1 1 ]
intToBits = x:
if x == 0 || x == -1 then
[]
else
let
headbit = if (x / 2) * 2 != x then 1 else 0; # x & 1
tailbits = if x < 0 then ((x + 1) / 2) - 1 else x / 2; # x >> 1
in
[headbit] ++ (intToBits tailbits);
# (bitsToInt [ 0 1 1 ] 0) -> 6
# (bitsToInt [ 0 1 0 ] 1) -> -6
bitsToInt = l: signum:
if l == [] then
(if signum == 0 then 0 else -1)
else
(builtins.head l) + (2 * (bitsToInt (builtins.tail l) signum));
xsignum = if x < 0 then 1 else 0;
ysignum = if y < 0 then 1 else 0;
zipListsWith' = fst: snd:
if fst==[] && snd==[] then
[]
else if fst==[] then
[(f xsignum (builtins.head snd))] ++ (zipListsWith' [] (builtins.tail snd))
else if snd==[] then
[(f (builtins.head fst) ysignum )] ++ (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)) (f xsignum ysignum);
in
rec {
/* The identity function
@ -31,6 +68,18 @@ rec {
/* 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);
/* bitwise “not” */
bitNot = builtins.sub (-1);
/* Convert a boolean to a string.
Note that toString on a bool returns "1" and "".
*/