Rice coding: Difference between revisions
Made this into a draft task and added a Wren example.
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(Made this into a draft task and added a Wren example.) |
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{{draft task}}
'''Rice coding''' is a variant of [[w:Golomb coding|Golomb coding]] where the parameter is a power of two. This makes it easier to encode the remainder of the euclidean division.
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is $_, decode encode $_ for -N..N;
}</syntaxhighlight>
=={{header|Wren}}==
{{trans|Julia}}
{{libheader|Wren-math}}
{{libheader|Wren-check}}
{{libheader|Wren-fmt}}
<syntaxhighlight lang="ecmascript">import "./math" for Int, Math
import "./check" for Check
import "./fmt" for Fmt
class Rice {
static encode(n, k) {
Check.nonNegInt("n", n)
var m = 1 << k
var q = Int.quo(n, m)
var r = n % m
var res = List.filled(q, 1)
res.add(0)
var digits = Int.digits(r, 2)
var dc = digits.count
if (dc < k + 1) res.addAll([0] * (k + 1 - dc))
res.addAll(digits)
return res
}
static encodeEx(n, k) { encode(n < 0 ? -2 * n - 1 : 2 * n, k) }
static decode(a, k) {
var m = 1 << k
var q = a.indexOf(0)
if (q == -1) q = 0
var r = Math.evalPoly(a[q..-1], 2)
return q * m + r
}
static decodeEx(a, k) {
var i = decode(a, k)
return i % 2 == 1 ? -Int.quo(i+1, 2) : Int.quo(i, 2)
}
}
System.print("Basic Rice coding:")
for (i in 0..10) {
var res = Rice.encode(i, 2)
Fmt.print("$2d -> $-6s -> $d", i, res.join(""), Rice.decode(res, 2))
}
System.print("\nExtended Rice coding")
for (i in -10..10) {
var res = Rice.encodeEx(i, 2)
Fmt.print("$3d -> $-9s -> $ d", i, res.join(""), Rice.decodeEx(res, 2))
}</syntaxhighlight>
{{out}}
<pre>
Basic Rice coding:
0 -> 0000 -> 0
1 -> 0001 -> 1
2 -> 0010 -> 2
3 -> 0011 -> 3
4 -> 10000 -> 4
5 -> 10001 -> 5
6 -> 10010 -> 6
7 -> 10011 -> 7
8 -> 110000 -> 8
9 -> 110001 -> 9
10 -> 110010 -> 10
Extended Rice coding
-10 -> 11110011 -> -10
-9 -> 11110001 -> -9
-8 -> 1110011 -> -8
-7 -> 1110001 -> -7
-6 -> 110011 -> -6
-5 -> 110001 -> -5
-4 -> 10011 -> -4
-3 -> 10001 -> -3
-2 -> 0011 -> -2
-1 -> 0001 -> -1
0 -> 0000 -> 0
1 -> 0010 -> 1
2 -> 10000 -> 2
3 -> 10010 -> 3
4 -> 110000 -> 4
5 -> 110010 -> 5
6 -> 1110000 -> 6
7 -> 1110010 -> 7
8 -> 11110000 -> 8
9 -> 11110010 -> 9
10 -> 111110000 -> 10
</pre>
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