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Manual Reference Pages  - switch (3m_strings)

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NAME

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

CONTENTS

Synopsis
Description
Examples
Author
License

SYNOPSIS

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

DESCRIPTION

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.

EXAMPLES

Sample program:

   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

Expected output

    > 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

AUTHOR

John S. Urban

LICENSE

Public Domain

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Nemo Release 3.1

switch (3m_strings)

January 10, 2025

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