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Manual Reference Pages  - i_is_prime (3)

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NAME

i_is_prime(3f) - [M_factor] Determine if a number is prime using Sieve of Erasthosthenes (LICENSE:???)

CONTENTS

Synopsis
Description
Version
Author
Parameters
Returns
Example

SYNOPSIS

function i_is_prime ( n )

    integer,intent(in) :: n

DESCRIPTION

A simple, unoptimized sieve of Erasthosthenes is used to check whether N can be divided by any integer between 2 and SQRT(N).

VERSION

29 November 1998

AUTHOR

John Burkardt

PARAMETERS

n	Input, integer N, the integer to be tested.

RETURNS

Output	logical I_IS_PRIME(3f) is TRUE if N is prime, and FALSE otherwise. Note that negative numbers and 0 are not considered prime.

EXAMPLE

sample program

   program demo_i_is_prime
   use M_factor, only: i_is_prime
   implicit none
   integer  :: i
   integer  :: icount=0
   integer  :: isum=0
   integer,parameter :: n= 10000
   do i=2, n
      if(i_is_prime(i))then
         icount=icount+1
         isum=isum+i
         write(*,*)icount,i
      endif
   enddo
   write(*,*)’number of primes between 2 and ’,n,’ is ’,icount
   write(*,*)’sum of primes between 2 and ’,n,’ is ’,isum
   write(*,*)i_is_prime([4,6,8,9,10,12,14,15,16,18])
   write(*,*)all(.not.i_is_prime([4,6,8,9,10,12,14,15,16,18]))
   write(*,*)any(.not.i_is_prime([4,6,8,9,10,12,14,15,16,18]))
   end program demo_i_is_prime

end program demo_i_is_prime

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i_is_prime (3)

March 11, 2021

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