diff options
Diffstat (limited to 'lib/trivial.nix')
| -rw-r--r-- | lib/trivial.nix | 43 |
1 files changed, 43 insertions, 0 deletions
diff --git a/lib/trivial.nix b/lib/trivial.nix index 251cb796db0..86e3c939dd6 100644 --- a/lib/trivial.nix +++ b/lib/trivial.nix @@ -1,4 +1,38 @@ { lib }: +let + zipIntBits = f: x: y: + let + # (intToBits 6) -> [ 0 1 1 ] + intToBits = x: + if x==0 then + [] + else + let + headbit = if (x / 2) * 2 != x then 1 else 0; # x & 1 + tailbits = if x < 0 then 9223372036854775807 + ((x+1) / 2) else x / 2; # x >>> 1 + in + [headbit] ++ (intToBits tailbits); + + # (bitsToInt [ 0 1 1 ]) -> 6 + bitsToInt = l: + if l==[] then + 0 + else + (builtins.head l) + (2 * (bitsToInt (builtins.tail l))); + + zipListsWith' = fst: snd: + if fst==[] && snd==[] then + [] + else if fst==[] then + [(f 0 (builtins.head snd))] ++ (zipListsWith' [] (builtins.tail snd)) + else if snd==[] then + [(f (builtins.head fst) 0 )] ++ (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)); +in rec { /* The identity function @@ -31,6 +65,15 @@ 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); + /* Convert a boolean to a string. Note that toString on a bool returns "1" and "". */ |