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TheXploder

Fri Feb 20, 2004 12:39 pm


Prime Number Finder

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Here is a program that finds prime numbers (divisible by itself and 1):


var c, number : int := 0

loop
    for decreasing i : number - 1 .. 2
        if number mod i > 0 then
            c := c + 1
        end if
    end for

    if c = number - 2 then
        put "Number: ", number, ", Prime number."
        c := 0
    else
        put "Number: ", number, ", is not a Prime number."
        c := 0
    end if

    number := number + 1
    delay(10)
end loop


This could be sead up a bit, if I cancel out all numbers with a 5 or 0 at the end, or the numbers that are divisible by a previous prime number, can't be prime anymore...

I used this website to check them aswell: http://www.utm.edu/research/primes/lists/small/1000.txt

If you like please play around with it and try to beat me at finding the prime numbers: I am currently at prime number: 12739

:D  :D  :D  :D  :D  :D  :D  :D  :D  :D  :D  :D  :D 

ohh, wait: 16229


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Tony

Fri Feb 20, 2004 2:10 pm



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maybe you should check out this [url=http://www.compsci.ca/v2/viewtopic.php?t=297&highlight=prime]tutorial :lol:


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the_short1

Sat Feb 21, 2004 11:11 pm



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hahah... yea Tony's prog... it worked in 12 sec to produce to 1million

produces a text file will all prime numbers in it...
from 2 > million
(with a 120 MHZ peice of crap)


WOW... that post is old too... 1y... at time when admins didnl;t have steady 2000 bits


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TheXploder

Sat Feb 21, 2004 11:46 pm



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thanx for that program Tony...


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Andy

Sun Feb 22, 2004 2:00 pm



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if u want a really good one, do some string manipulation, so u can store 255 digit numbers


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Tony

Sun Feb 22, 2004 11:47 pm



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why not just use a char array then? you can make your arrays much larger then 255 :lol:


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Andy

Mon Feb 23, 2004 10:49 am



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good point


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Andy

Mon Feb 23, 2004 10:50 am



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how about a flexiable array of strings?


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rizzix

Tue Feb 24, 2004 11:59 pm



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aah but turing arrays have a limit of 1M elements.

using a string class i created will let u manipulate on an infinite number of characters.  :P (or maybe untill u exhaust all the free memory in RAM)


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Tony

Wed Feb 25, 2004 12:58 am



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you can always start writing numbers down on your harddrive :lol:


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BlAcK TuRtLe

Sun Feb 29, 2004 2:34 pm



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This is a variation of your code which lets the user enter a number then finds out whether or not its prime.

var x, num : int := 0
loop
    put "Enter a number(-99 to exit)"
    get num
    exit when num = -99
    for decreasing y : num - 1 .. 2
        if num mod y > 0 then
            x := x + 1
        end if
    end for
    if x = num - 2 then
        put num, ", is a prime number."
        x := 0
    else
        put num, ", is not a Prime number."
        x := 0
    end if
    delay (2000)
    cls
end loop
cls