Extract substring of Fortran string array

Question

How does one extract a substring of a Fortran string array? For example

program testcharindex
    implicit none
    character(len=10), dimension(5) :: s
             


        

Answer 1

In case loop is to be avoided and there is no other (simple) methods, it might be useful to define an elemental substring function and apply it to an array of strings. For example,

module str_mod
    implicit none
contains
    elemental function substr( s, a, b ) result( res )
        character(*), intent(in) :: s
        integer,      intent(in) :: a, b
        character(len(s)) :: res

        res = s( a : b )
    endfunction
endmodule

program main
    use str_mod
    implicit none
    character(10) :: s( 5 )
    integer, allocatable :: ind(:)
    character(len(s)), allocatable :: comp(:)

    s = [ '1_E ', '2_S ', '3_E ', '14_E', '25_S' ]
    ! s = [ character(len(s)) :: '1_E', '2_S', '3_E', '14_E', '25_S' ]

    print *, "test(scalar) : ", substr( s(1), 1, 2 )
    print *, "test(array ) : ", substr( s,    1, 2 )

    ind = index( s, '_' )
    comp = substr( s, 1, ind-1 )

    print *
    print *, "string (all)    : ", s
    print *, "string before _ : ", comp
    print *, "string after _  : ", substr( s, ind+1, len(s) )
endprogram

which gives (with gfortran-7.3)

 test(scalar) : 1_        
 test(array ) : 1_        2_        3_        14        25        

 string (all)    : 1_E       2_S       3_E       14_E      25_S      
 string before _ : 1         2         3         14        25        
 string after _  : E         S         E         E         S