diff --git a/lib/trivial.nix b/lib/trivial.nix index a36056253d7..b75e81eb735 100644 --- a/lib/trivial.nix +++ b/lib/trivial.nix @@ -1,41 +1,5 @@ { 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 { ## Simple (higher order) functions @@ -71,13 +35,19 @@ rec { and = x: y: x && y; /* bitwise “and” */ - bitAnd = builtins.bitAnd or zipIntBits (a: b: if a==1 && b==1 then 1 else 0); + bitAnd = builtins.bitAnd + or import ./zip-int-bits.nix + (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); + bitOr = builtins.bitOr + or import ./zip-int-bits.nix + (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); + bitXor = builtins.bitXor + or import ./zip-int-bits.nix + (a: b: if a!=b then 1 else 0); /* bitwise “not” */ bitNot = builtins.sub (-1); diff --git a/lib/zip-int-bits.nix b/lib/zip-int-bits.nix new file mode 100644 index 00000000000..edbcdfe1e68 --- /dev/null +++ b/lib/zip-int-bits.nix @@ -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)