switch Interface

switch(3f) - [M_strings:ARRAY] converts between CHARACTER scalar and
array of single characters
(LICENSE:PD)

pure function switch(array) result (string)

 character(len=1),intent(in) :: array(:)
 character(len=SIZE(array))  :: string

  or

pure function switch(string) result (array)

 character(len=1),intent(in) :: array(:)
 character(len=SIZE(array))  :: string

SWITCH(3f): generic function that switches CHARACTER string to an array
of single characters or an array of single characters to a CHARACTER
string. Useful in passing strings to C. New Fortran features may
supersede these routines.

program demo_switch
use M_strings, only : switch, isalpha, islower, nospace
character(len=*),parameter :: &
& dashes='-----------------------------------'
character(len=*),parameter :: string='This is a string'
character(len=1024)        :: line

! First, examples of standard Fortran features
! returns array [F,T,T,T,T,T]
write(*,*)['A','=','=','=','=','='] == '='
! this would return T
write(*,*)all(['=','=','=','=','=','='] == '=')
! this would return F
write(*,*)all(['A','=','=','=','=','='] == '=')

! so to test if the string DASHES is all dashes
! using SWITCH(3f) is
if(all(switch(dashes) == '-'))then
   write(*,*)'DASHES is all dashes'
endif

! so to test is a string is all letters
! isalpha(3f) returns .true. only if character is a letter
! false because dashes are not a letter
write(*,*) all(isalpha(switch(dashes)))
! false because of spaces
write(*,*) all(isalpha(switch(string)))
! true because removed whitespace
write(*,*) all(isalpha(switch(nospace(string))))

! to see if a string is all uppercase
! show the string
write(*,*) string
! converted to character array
write(*,'(1x,*("[",a,"]":))') switch(string)
write(*,'(*(l3))') islower(switch(string))

! we need a string that is all letters
line=nospace(string)
write(*,*)'LINE=',trim(line)
! all true except first character
write(*,*) islower(switch(nospace(string)))
! should be false
write(*,*) all(islower(switch(nospace(string))))
! should be true
write(*,*) all(islower(switch(nospace(string(2:)))))

end program demo_switch

 F T T T T T
 T
 F
 DASHES is all dashes
 F
 F
 T
 This is a string
 [T][h][i][s][ ][i][s][ ][a][ ][s][t][r][i][n][g]
  F  T  T  T  F  T  T  F  T  F  T  T  T  T  T  T
 LINE=Thisisastring
 F T T T T T T T T T T T T
 F
 T

John S. Urban

Public Domain