Padding function for https://github.com/fortran-lang/stdlib/issues/394

pad_mod.f90

module pad_mod

  implicit none

  interface padl
    module procedure padl_blank
    module procedure padl_char
  end interface

  interface padr
    module procedure padr_blank
    module procedure padr_char
  end interface

contains

  function padl_blank(str,width) result(res)
    character(len=*), intent(in) :: str
    integer, intent(in) :: width
    character(len=max(len_trim(str),width)) :: res
    res = str
    res = adjustr(res)
  end function

  function padr_blank(str,width) result(res)
    character(len=*), intent(in) :: str
    integer, intent(in) :: width
    character(len=max(len_trim(str),width)) :: res
    res = str
  end function

  function padl_char(str,width,char) result(res)
    character(len=*), intent(in) :: str
    integer, intent(in) :: width
    character(len=1) :: char
    character(len=max(len_trim(str),width)) :: res
    integer :: nchar
    nchar = width - len_trim(str)
    if (nchar <= 0) then
      res = str
    else
      res = repeat(char,nchar)//str
    end if
  end function

  function padr_char(str,width,char) result(res)
    character(len=*), intent(in) :: str
    integer, intent(in) :: width
    character(len=1) :: char
    character(len=max(len_trim(str),width)) :: res
    integer :: nchar
    nchar = width - len_trim(str)
    if (nchar <= 0) then
      res = str
    else
      res = str//repeat(char,nchar)
    end if
  end function
end module

program test_pad

  use pad_mod
  implicit none

  print *, "Hello"
  print *, padl("Hello",10)
  print *, padr("Hello",12), len(padr("Hello",12))

  print *, padl("Hello",10,'0')
  print *, padr("Hello",10,'0')


  print *, padl(padr("End",7,'_'),11,'_')

end program