Pseudo-random numbers/Middle-square method: Difference between revisions
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=={{header|C++}}== |
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<lang cpp>#include <exception> |
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#include <iostream> |
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using ulong = unsigned long; |
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class MiddleSquare { |
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private: |
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ulong state; |
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ulong div, mod; |
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public: |
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MiddleSquare() = delete; |
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MiddleSquare(ulong start, ulong length) { |
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if (length % 2) throw std::invalid_argument("length must be even"); |
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div = mod = 1; |
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for (ulong i=0; i<length/2; i++) div *= 10; |
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for (ulong i=0; i<length; i++) mod *= 10; |
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state = start % mod; |
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} |
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ulong next() { |
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return state = state * state / div % mod; |
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} |
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}; |
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int main() { |
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MiddleSquare msq(675248, 6); |
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for (int i=0; i<5; i++) |
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std::cout << msq.next() << std::endl; |
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return 0; |
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}</lang> |
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{{out}} |
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<pre>959861 |
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333139 |
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981593 |
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524817 |
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432883</pre> |
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=={{header|CLU}}== |
=={{header|CLU}}== |
Revision as of 19:45, 2 January 2022
You are encouraged to solve this task according to the task description, using any language you may know.
- Middle-square_method Generator
- The Method
To generate a sequence of n-digit pseudorandom numbers, an n-digit starting value is created and squared, producing a 2n-digit number. If the result has fewer than 2n digits, leading zeroes are added to compensate. The middle n digits of the result would be the next number in the sequence and returned as the result. This process is then repeated to generate more numbers.
- Pseudo code
var seed = 675248 function random() var s = str(seed * seed) 'str: turn a number into string do while not len(s) = 12 s = "0" + s 'add zeroes before the string end do seed = val(mid(s, 4, 6)) 'mid: string variable, start, length 'val: turn a string into number return seed end function
- Middle-square method use
for i = 1 to 5 print random() end for
- Task
- Generate a class/set of functions that generates pseudo-random
numbers (6 digits) as shown above.
- Show the first five integers generated with the seed 675248 as shown above.
- Show your output here, on this page.
ALGOL 68
Uses (long) integers. <lang algol68>BEGIN # generate random numbers by the middle-square method #
INT seed := 675248; # returns the next middle-square random number # PROC ms random = INT: seed := SHORTEN( ( ( LONG INT( seed ) * LONG INT( seed ) ) OVER 1000 ) MOD 1 000 000 ); # test the ms random procedure # FOR i TO 5 DO print( ( " ", whole( ms random, 0 ) ) ) OD
END</lang>
- Output:
959861 333139 981593 524817 432883
C++
<lang cpp>#include <exception>
- include <iostream>
using ulong = unsigned long;
class MiddleSquare { private:
ulong state; ulong div, mod;
public:
MiddleSquare() = delete; MiddleSquare(ulong start, ulong length) { if (length % 2) throw std::invalid_argument("length must be even"); div = mod = 1; for (ulong i=0; i<length/2; i++) div *= 10; for (ulong i=0; i<length; i++) mod *= 10; state = start % mod; } ulong next() { return state = state * state / div % mod; }
};
int main() {
MiddleSquare msq(675248, 6); for (int i=0; i<5; i++) std::cout << msq.next() << std::endl; return 0;
}</lang>
- Output:
959861 333139 981593 524817 432883
CLU
<lang clu>middle_square = cluster is seed, next
rep = null own state: int seed = proc (s: int) state := s end seed next = proc () returns (int) state := (state ** 2) / 1000 // 1000000 return(state) end next
end middle_square
start_up = proc ()
po: stream := stream$primary_output() middle_square$seed(675248) for i: int in int$from_to(1, 5) do stream$putl(po, int$unparse(middle_square$next())) end
end start_up</lang>
- Output:
959861 333139 981593 524817 432883
COBOL
<lang cobol> IDENTIFICATION DIVISION.
PROGRAM-ID. MIDDLE-SQUARE. DATA DIVISION. WORKING-STORAGE SECTION. 01 STATE. 03 SEED PIC 9(6) VALUE 675248. 03 SQUARE PIC 9(12). 03 FILLER REDEFINES SQUARE. 05 FILLER PIC 9(3). 05 NEXT-SEED PIC 9(6). 05 FILLER PIC 9(3). PROCEDURE DIVISION. BEGIN. PERFORM SHOW-NUM 5 TIMES. STOP RUN. SHOW-NUM. PERFORM MAKE-RANDOM. DISPLAY SEED. MAKE-RANDOM. MULTIPLY SEED BY SEED GIVING SQUARE. MOVE NEXT-SEED TO SEED.</lang>
- Output:
959861 333139 981593 524817 432883
FreeBASIC
<lang freebasic>Dim Shared seed As Integer = 675248 Dim i As Integer Declare Function Rand As Integer For i = 1 To 5 Print Rand Next i Sleep
Function Rand As Integer Dim s As String s = Str(seed ^ 2) Do While Len(s) <> 12 s = "0" + s Loop seed = Val(Mid(s, 4, 6)) Rand = seed End Function </lang>
Perl
<lang perl>#!/usr/bin/perl
use strict; # https://rosettacode.org/wiki/Pseudo-random_numbers/Middle-square_method use warnings;
sub msq
{ use feature qw( state ); state $seed = 675248; $seed = sprintf "%06d", $seed ** 2 / 1000 % 1e6; }
print msq, "\n" for 1 .. 5;</lang>
- Output:
959861 333139 981593 524817 432883
Phix
You don't actually have to use strings, but should you so desire the commented-out line gives exactly the same results. Output matches Python.
with javascript_semantics integer seed = 675248 function random() seed = remainder(floor(seed*seed/1000),1e6) -- seed = to_integer(sprintf("%012d",seed*seed)[4..9]) return seed end function for i=1 to 5 do ?random() end for
Python
<lang python>seed = 675248 def random():
global seed s = str(seed ** 2) while len(s) != 12: s = "0" + s seed = int(s[3:9]) return seed
for i in range(0,5):
print(random())
</lang>
- Output:
959861 333139 981593 524817 432883
Raku
<lang perl6>sub msq {
state $seed = 675248; $seed = $seed² div 1000 mod 1000000;
}
say msq() xx 5;</lang>
- Output:
(959861 333139 981593 524817 432883)
Wren
<lang ecmascript>var random = Fn.new { |seed| ((seed * seed)/1e3).floor % 1e6 }
var seed = 675248 for (i in 1..5) System.print(seed = random.call(seed))</lang>
- Output:
959861 333139 981593 524817 432883