The amount of implementation detail really should not be the first thing in a prominent file called `trivial.nix`.wip/yesman
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/* Helper function to implement a fallback for the bit operators |
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`bitAnd`, `bitOr` and `bitXOr` on older nix version. |
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See ./trivial.nix |
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*/ |
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f: x: y: |
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let |
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# (intToBits 6) -> [ 0 1 1 ] |
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intToBits = x: |
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if x == 0 || x == -1 then |
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[] |
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else |
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let |
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headbit = if (x / 2) * 2 != x then 1 else 0; # x & 1 |
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tailbits = if x < 0 then ((x + 1) / 2) - 1 else x / 2; # x >> 1 |
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in |
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[headbit] ++ (intToBits tailbits); |
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# (bitsToInt [ 0 1 1 ] 0) -> 6 |
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# (bitsToInt [ 0 1 0 ] 1) -> -6 |
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bitsToInt = l: signum: |
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if l == [] then |
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(if signum == 0 then 0 else -1) |
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else |
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(builtins.head l) + (2 * (bitsToInt (builtins.tail l) signum)); |
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xsignum = if x < 0 then 1 else 0; |
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ysignum = if y < 0 then 1 else 0; |
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zipListsWith' = fst: snd: |
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if fst==[] && snd==[] then |
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[] |
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else if fst==[] then |
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[(f xsignum (builtins.head snd))] ++ (zipListsWith' [] (builtins.tail snd)) |
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else if snd==[] then |
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[(f (builtins.head fst) ysignum )] ++ (zipListsWith' (builtins.tail fst) [] ) |
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else |
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[(f (builtins.head fst) (builtins.head snd))] ++ (zipListsWith' (builtins.tail fst) (builtins.tail snd)); |
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in |
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assert (builtins.isInt x) && (builtins.isInt y); |
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bitsToInt (zipListsWith' (intToBits x) (intToBits y)) (f xsignum ysignum) |
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