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

* 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

View file

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

View file

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

View file

@ -1,4 +1,41 @@
{ lib }: { 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 { rec {
/* The identity function /* The identity function
@ -31,6 +68,18 @@ rec {
/* boolean and */ /* boolean and */
and = x: y: x && y; 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. /* Convert a boolean to a string.
Note that toString on a bool returns "1" and "". Note that toString on a bool returns "1" and "".
*/ */