mirror of
https://github.com/anoma/juvix.git
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52 lines
2.4 KiB
Plaintext
52 lines
2.4 KiB
Plaintext
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-- This file implements the mid-square hashing function in JuvixCore. See:
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-- https://research.cs.vt.edu/AVresearch/hashing/midsquare.php
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--
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-- The implementation is for hashing natural numbers with maximum 16 bits into 6
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-- bits. In order to facilitate the translation to the current version of the
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-- GEB backend, no recursion is used (it is manually unrolled).
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--
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-- `powN` is 2 ^ N
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def pow0 : Int := 1;
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def pow1 : Int := 2 * pow0;
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def pow2 : Int := 2 * pow1;
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def pow3 : Int := 2 * pow2;
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def pow4 : Int := 2 * pow3;
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def pow5 : Int := 2 * pow4;
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def pow6 : Int := 2 * pow5;
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def pow7 : Int := 2 * pow6;
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def pow8 : Int := 2 * pow7;
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def pow9 : Int := 2 * pow8;
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def pow10 : Int := 2 * pow9;
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def pow11 : Int := 2 * pow10;
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def pow12 : Int := 2 * pow11;
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def pow13 : Int := 2 * pow12;
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def pow14 : Int := 2 * pow13;
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def pow15 : Int := 2 * pow14;
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def pow16 : Int := 2 * pow15;
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-- `hashN` hashes a number with max N bits (i.e. smaller than 2^N) into 6 bits
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-- (i.e. smaller than 64) using the mid-square algorithm.
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def hash0 : Int -> Int := \(x : Int) 0;
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def hash1 : Int -> Int := \(x : Int) x * x;
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def hash2 : Int -> Int := \(x : Int) x * x;
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def hash3 : Int -> Int := \(x : Int) x * x;
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def hash4 : Int -> Int := \(x : Int) if x < pow3 then hash3 x else ((x * x) / pow1) % pow6;
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def hash5 : Int -> Int := \(x : Int) if x < pow4 then hash4 x else ((x * x) / pow2) % pow6;
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def hash6 : Int -> Int := \(x : Int) if x < pow5 then hash5 x else ((x * x) / pow3) % pow6;
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def hash7 : Int -> Int := \(x : Int) if x < pow6 then hash6 x else ((x * x) / pow4) % pow6;
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def hash8 : Int -> Int := \(x : Int) if x < pow7 then hash7 x else ((x * x) / pow5) % pow6;
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def hash9 : Int -> Int := \(x : Int) if x < pow8 then hash8 x else ((x * x) / pow6) % pow6;
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def hash10 : Int -> Int := \(x : Int) if x < pow9 then hash9 x else ((x * x) / pow7) % pow6;
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def hash11 : Int -> Int := \(x : Int) if x < pow10 then hash10 x else ((x * x) / pow8) % pow6;
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def hash12 : Int -> Int := \(x : Int) if x < pow11 then hash11 x else ((x * x) / pow9) % pow6;
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def hash13 : Int -> Int := \(x : Int) if x < pow12 then hash12 x else ((x * x) / pow10) % pow6;
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def hash14 : Int -> Int := \(x : Int) if x < pow13 then hash13 x else ((x * x) / pow11) % pow6;
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def hash15 : Int -> Int := \(x : Int) if x < pow14 then hash14 x else ((x * x) / pow12) % pow6;
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def hash16 : Int -> Int := \(x : Int) if x < pow15 then hash15 x else ((x * x) / pow13) % pow6;
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def hash : Int -> Int := hash16;
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hash 1367
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-- result: 3
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