The amount of implementation detail really should not be the first thing in a prominent file called `trivial.nix`.wip/yesman
parent
af10842940
commit
62dca7c9ab
@ -0,0 +1,39 @@ |
||||
/* 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) |
Loading…
Reference in new issue