Manual Reference Pages - swap (3)
NAME
swap(3f) - [M_sort] elemental subroutine swaps two standard type variables of like type
CONTENTS
Synopsis
Description
Example
SYNOPSIS
subroutine swap(X,Y)
DESCRIPTION
Generic subroutine SWAP(GEN1,GEN2) swaps two variables of like type (real, integer, complex, character, double, logical).On output, the values of X and Y have been interchanged. Swapping is commonly required in procedures that sort data.
SWAP(3f) is elemental, so it can operate on vectors and arrays as well as scalar values.
EXAMPLE
Example program:
program demo_swap use M_sort, only : swap integer :: iarray(2)=[10,20] real :: rarray(2)=[11.11,22.22] doubleprecision :: darray(2)=[1234.56789d0,9876.54321d0] complex :: carray(2)=[(1234,56789),(9876,54321)] logical :: larray(2)=[.true.,.false.] character(len=16) :: string(2)=["First string ","The other string"]integer :: one(13)=1 integer :: two(13)=2
integer :: one2(3,3)=1 integer :: two2(3,3)=2
print *, "integers before swap ", iarray call swap (iarray(1), iarray(2)) print *, "integers after swap ", iarray
print *, "reals before swap ", rarray call swap (rarray(1), rarray(2)) print *, "reals after swap ", rarray
print *, "doubles before swap ", darray call swap (darray(1), darray(2)) print *, "doubles after swap ", darray
print *, "complexes before swap ", carray call swap (carray(1), carray(2)) print *, "complexes after swap ", carray
print *, "logicals before swap ", larray call swap (larray(1), larray(2)) print *, "logicals after swap ", larray
print *, "strings before swap ", string call swap (string(1), string(2)) print *, "strings after swap ", string
write(*,*)’swap two vectors’ write(*,’("one before: ",*(i0,:","))’) one write(*,’("two before: ",*(i0,:","))’) two call swap(one,two) write(*,’("one after: ",*(i0,:","))’) one write(*,’("two after: ",*(i0,:","))’) two
write(*,*)’given these arrays initially each time ’ one2=1 two2=2 call printarrays()
write(*,*)’swap two rows’ one2=1 two2=2 call swap(one2(2,:),two2(3,:)) call printarrays()
write(*,*)’swap two columns’ one2=1 two2=2 call swap(one2(:,2),two2(:,2)) call printarrays()
write(*,*)’swap two arrays with same number of elements’ one2=1 two2=2 call swap(one2,two2) call printarrays()
contains subroutine printarrays() integer :: i do i=1,size(one2(1,:)) write(*,’(*(i0,:","))’) one2(i,:) enddo write(*,*) do i=1,size(two2(1,:)) write(*,’(*(i0,:","))’) two2(i,:) enddo end subroutine printarrays
end program demo_swapExpected Results:
> integers before swap 10 20 > integers after swap 20 10 > reals before swap 11.1099997 22.2199993 > reals after swap 22.2199993 11.1099997 > doubles before swap 1234.5678900000000 9876.5432099999998 > doubles after swap 9876.5432099999998 1234.5678900000000 > complexes before swap ( 1234.00000 , 56789.0000 ) ( 9876.00000 , 54321.0000 ) > complexes after swap ( 9876.00000 , 54321.0000 ) ( 1234.00000 , 56789.0000 ) > logicals before swap T F > logicals after swap F T > strings before swap First string The other string > strings after swap The other stringFirst string > swap two vectors >one before: 1,1,1,1,1,1,1,1,1,1,1,1,1 >two before: 2,2,2,2,2,2,2,2,2,2,2,2,2 >one after: 2,2,2,2,2,2,2,2,2,2,2,2,2 >two after: 1,1,1,1,1,1,1,1,1,1,1,1,1 > given these arrays initially each time >1,1,1 >1,1,1 >1,1,1 > >2,2,2 >2,2,2 >2,2,2 > swap two rows >1,1,1 >2,2,2 >1,1,1 > >2,2,2 >2,2,2 >1,1,1 > swap two columns >1,2,1 >1,2,1 >1,2,1 > >2,1,2 >2,1,2 >2,1,2 > swap two arrays with same number of elements >2,2,2 >2,2,2 >2,2,2 > >1,1,1 >1,1,1 >1,1,1
| swap (3) | October 17, 2020 |
