Manual Reference Pages - ncr (3)
NAME
ncr(3f) - [M_math] Calculate the number of unique combinations of r objects out of n.
CONTENTS
Synopsis
Description
Options
Example
Author
SYNOPSIS
subroutine ncr(n,r,ncomb,ier)
integer, intent(in) :: n
integer, intent(in) :: r
!!integer, parameter :: dp = selected_real_kind(12, 60)
integer, parameter :: dp = kind(0.0d0)
real (dp), intent(out) :: ncomb
integer, intent(out) :: ier
DESCRIPTION
Calculate the number of unique combinations of r objects out of n.
OPTIONS
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ier |
returns error code
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o
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0 if no error is detected
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o
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1 if n < 1
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o
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2 if r < 0
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o
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3 if r > n
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o
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4 if nCr > 1.e+308, i.e. if it overflows. In this case, the
natural log of nCr is returned.
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EXAMPLE
Sample program:
program demo_ncr
use m_math, only : ncr
implicit none
integer, parameter :: dp = selected_real_kind(12, 60)
integer :: n, r, ier
real (dp) :: result
do
write(*, ’(a)’, advance=’no’) ’ Enter n, r : ’
read(*, *) n, r
call ncr(n, r, result, ier)
if (ier /= 0) then
write(*, *) ’ Error, IER = ’, ier
if (ier == 4) write(*, ’(a, f12.5)’) ’ ln(ncr) = ’, result
else
write(*, ’(a, g16.8)’) ’ ncr = ’, result
endif
enddo
end program demo_ncr
AUTHOR
Alan Miller
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