Loops/Increment loop index within loop body: Difference between revisions
Loops/Increment loop index within loop body (view source)
Revision as of 14:17, 17 March 2019
, 5 years agoRealize in F#
(Undo revision 278942 by Nigel Galloway (talk)) |
(Realize in F#) |
||
Line 425:
</pre>
=={{header|F_Sharp|F#}}==
This task uses [http://www.rosettacode.org/wiki/Extensible_prime_generator#The_function Extensible Prime Generator (F#)]
<lang fsharp>
// Well I don't do loops. Nigel Galloway: March 17th., 2019. Let me try to explain where the loopy variables are, for the imperatively constrained.
// cUL allows me to claim the rather trivial extra credit (commas in the numbers)
let cUL=let g=System.Globalization.CultureInfo("en-GB") in (fun (n:uint64)->n.ToString("N0",g))
// fN is primality by trial division
let fN g=pCache|>Seq.map uint64|>Seq.takeWhile(fun n->n*n<g)|>Seq.forall(fun n->g%n>0UL)
// unfold is sort of a loop incremented by 1 in this case
let fG n=Seq.unfold(fun n->Some(n,(n+1UL))) n|>Seq.find(fN)
// unfold is sort of a loop with fG as an internal loop incremented by twice the exit value of the internal loop in this case.
Seq.unfold(fun n->let n=fG n in Some(n,n+n)) 42UL|>Seq.take 42|>Seq.iteri(fun n g->printfn "%2d -> %s" (n+1) (cUL g))
</lang>
{{out}}
<pre>
1 -> 43
2 -> 89
3 -> 179
4 -> 359
5 -> 719
6 -> 1,439
7 -> 2,879
8 -> 5,779
9 -> 11,579
10 -> 23,159
11 -> 46,327
12 -> 92,657
13 -> 185,323
14 -> 370,661
15 -> 741,337
16 -> 1,482,707
17 -> 2,965,421
18 -> 5,930,887
19 -> 11,861,791
20 -> 23,723,597
21 -> 47,447,201
22 -> 94,894,427
23 -> 189,788,857
24 -> 379,577,741
25 -> 759,155,483
26 -> 1,518,310,967
27 -> 3,036,621,941
28 -> 6,073,243,889
29 -> 12,146,487,779
30 -> 24,292,975,649
31 -> 48,585,951,311
32 -> 97,171,902,629
33 -> 194,343,805,267
34 -> 388,687,610,539
35 -> 777,375,221,081
36 -> 1,554,750,442,183
37 -> 3,109,500,884,389
38 -> 6,219,001,768,781
39 -> 12,438,003,537,571
40 -> 24,876,007,075,181
41 -> 49,752,014,150,467
42 -> 99,504,028,301,131
</pre>
=={{header|Factor}}==
Explicit loop indices are non-idiomatic, but Factor is certainly capable of using them. Factor has a for loop near-equivalent, <code><range> [ ] each</code>, but since it doesn't mesh well with mutation, a while loop is used.
| |||