From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.3 required=5.0 tests=BAYES_00,INVALID_MSGID
	autolearn=no autolearn_force=no version=3.4.4
X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,4117034ae215d480
X-Google-Attributes: gid103376,public
From: "E. Robert Tisdale" <edwin@netwood.net>
Subject: Re: Prime number program?
Date: 1999/12/04
Message-ID: <38499490.1C8AEE2B@netwood.net>#1/1
X-Deja-AN: 556680025
Content-Transfer-Encoding: 7bit
References: <82bk0d$55b$1@saturn.bton.ac.uk>
X-Accept-Language: en
Content-Type: text/plain; charset=us-ascii
X-Complaints-To: newsabuse@supernews.com
Organization: Posted via Supernews, http://www.supernews.com
MIME-Version: 1.0
Newsgroups: comp.lang.ada
Date: 1999-12-04T00:00:00+00:00
List-Id: <comp.lang.ada>

Oly wrote:

> I have to build an Ada program which tells the user
> if the number which they have entered is a prime number or not.
> I am still a newbie at Ada (and crap at maths)
> and have spent many wasted and frustrating hours
> trying to solve the problem.

I used Lycos to search for +prime +number +algorithm
and I found lots of stuff including

    http://www.utm.edu/research/primes/

It is very hard to determine whether or not a number n is prime
and that is one of the reasons why prime number figure
very prominently in encryption algorithms.
Suppose that the square root of n is not an integer.
Then you will need to test whether n/p is an integer
for every prime number p < sqrt(n)
which means that you need a list
of all the prime numbers p < sqrt(n).
Programs which find all the prime numbers
in a range of integers are called prime number sieves.
The one on my computer is called "primes."

    $ primes 0 10
    2
    3
    5
    7
    $

Hope this helps, E. Robert Tisdale <edwin@netwood.net>