62dca7c9ab
The amount of implementation detail really should not be the first thing in a prominent file called `trivial.nix`.
40 lines
1.4 KiB
Nix
40 lines
1.4 KiB
Nix
/* Helper function to implement a fallback for the bit operators
|
|
`bitAnd`, `bitOr` and `bitXOr` on older nix version.
|
|
See ./trivial.nix
|
|
*/
|
|
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)
|