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Diffstat (limited to 'std/Number/Pairing.bruijn')
| -rw-r--r-- | std/Number/Pairing.bruijn | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/std/Number/Pairing.bruijn b/std/Number/Pairing.bruijn new file mode 100644 index 0000000..a3a7e4a --- /dev/null +++ b/std/Number/Pairing.bruijn @@ -0,0 +1,24 @@ +# MIT License, Copyright (c) 2024 Marvin Borner +# pairing functions for writing two integers as one, bijectionally + +:import std/Logic . +:import std/Pair . +:import std/Number . +:import std/Math . + +# strong Rosenberg pairing function +pair-ternary [[[0 ⋅ 0 + 0 + 2 - 1] (max 1 0)]] ⧗ Number → Number → Number + +:test ((pair-ternary (+0) (+0)) =? (+0)) (true) +:test ((pair-ternary (+0) (+1)) =? (+1)) (true) +:test ((pair-ternary (+1) (+0)) =? (+3)) (true) +:test ((pair-ternary (+2) (+1)) =? (+7)) (true) + +# strong Rosenberg unpairing function +unpair-ternary [[[go] (1 - (0 ⋅ 0))] (sqrt 0)] ⧗ Number → (Pair Number Number) + go (0 <? 1) (0 : 1) (1 : (1 ⋅ 1 + 1 + 1 - 2)) + +:test (strip <$> (unpair-ternary (+0))) ((+0) : (+0)) +:test (strip <$> (unpair-ternary (+1))) ((+0) : (+1)) +:test (strip <$> (unpair-ternary (+3))) ((+1) : (+0)) +:test (strip <$> (unpair-ternary (+7))) ((+2) : (+1)) |