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Hamming numbers: Difference between revisions
→{{header|Clojure}}
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(cons 1 (smerge3 (map*n 2 hamming) (map*n 3 hamming) (map*n 5 hamming)))))</lang>
Note that this version uses a lot of space and time after calculating a few hundred thousand elements of the sequence. This is no doubt due to its "holding on to the head": it maintains the entire generated sequence in memory.
=={{header|D}}==
D V2 version, from the Java version. This version keeps the whole sequence in memory.
<lang d>import std.stdio: writeln;
import std.bigint: BigInt;
import std.algorithm: min, map;
import std.range: iota;
import std.array: array;
BigInt hamming(int limit) {
BigInt two = 2;
BigInt three = 3;
BigInt five = 5;
auto h = new BigInt[limit];
h[0] = 1;
BigInt x2 = 2;
BigInt x3 = 3;
BigInt x5 = 5;
int i, j, k;
foreach (ref el; h[1 .. $]) {
el = min(x2, x3, x5);
if (x2 == el)
x2 = two * h[++i];
if (x3 == el)
x3 = three * h[++j];
if (x5 == el)
x5 = five * h[++k];
}
return h[$ - 1];
}
const(char)[] bigIntRepr(BigInt i) {
const(char)[] result;
i.toString((const(char)[] s){ result = s; }, "d");
return result;
}
void main() {
writeln(array(map!bigIntRepr(map!hamming(iota(1, 21)))));
writeln(bigIntRepr(hamming(1691)));
writeln(bigIntRepr(hamming(1_000_000)));
}</lang>
Output:
<pre>1 2 3 4 5 6 8 9 10 12 15 16 18 20 24 25 27 30 32 36
2125764000
519312780448388736089589843750000000000000000000000000000000000000000000000000000000</pre>
=={{header|Factor}}==
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