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Pythagorean triples: Difference between revisions
→{{header|Forth}}
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</lang>
=={{header|Fortran}}==
{{works with|Fortran|90 and later}}
{{trans|C efficient method}}
<lang fortran>module triples
implicit none
integer :: max_peri, prim, total
integer :: u(9,3) = reshape((/ 1, -2, 2, 2, -1, 2, 2, -2, 3, &
1, 2, 2, 2, 1, 2, 2, 2, 3, &
-1, 2, 2, -2, 1, 2, -2, 2, 3 /), &
(/ 9, 3 /))
contains
recursive subroutine new_tri(in)
integer, intent(in) :: in(:)
integer :: i
integer :: t(3), p
p = sum(in)
if (p > max_peri) return
prim = prim + 1
total = total + max_peri / p
do i = 1, 3
t(1) = sum(u(1:3, i) * in)
t(2) = sum(u(4:6, i) * in)
t(3) = sum(u(7:9, i) * in)
call new_tri(t);
end do
end subroutine new_tri
end module triples
program Pythagorean
use triples
implicit none
integer :: seed(3) = (/ 3, 4, 5 /)
max_peri = 10
do
total = 0
prim = 0
call new_tri(seed)
write(*, "(a, i10, 2(i10, a))") "Up to", max_peri, total, " triples", prim, " primitives"
if(max_peri == 100000000) exit
max_peri = max_peri * 10
end do
end program Pythagorean</lang>
Output:<pre>Up to 10 0 triples 0 primitives
Up to 100 17 triples 7 primitives
Up to 1000 325 triples 70 primitives
Up to 10000 4858 triples 703 primitives
Up to 100000 64741 triples 7026 primitives
Up to 1000000 808950 triples 70229 primitives
Up to 10000000 9706567 triples 702309 primitives
Up to 100000000 113236940 triples 7023027 primitives</pre>
=={{header|Fortran}}==
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