Allocatable character variables in Fortran

11
votes

My code (stripped down to what I think is relevant for this question) is

PROGRAM test

IMPLICIT NONE

CHARACTER(len=37) input
CHARACTER(len=:), allocatable :: input_trim


WRITE(*,*) 'Filename?'
READ(*,*) input
ALLOCATE(character(len=LEN(TRIM(input))) :: input_trim)
input_trim=trim(input)

.
.
.

END PROGRAM test

It works fine with Intel's Fortran compiler, however gfortran gives me a couple of errors, the first one being in the line saying

CHARACTER(len=:), allocatable :: input_trim

I'm not sure which compiler is 'right' regarding the Fortran standard. Plus I don't know how to achieve what I need in a different way?! I think what I'm doing is more of a workaround anyway. What I need is a character variable containing exactly the filename that was entered with no following spaces.

EDIT: The error is "Syntax error in CHARACTER declaration". gfortran --version gives me "GNU Fortran (GCC) 4.4.7 20120313 (Red Hat 4.4.7-3)"

EDIT 2: You're right regarding the allocate: With ifort, I don't need it. And gfortran crashes before that so maybe it doesn't need the allocate either but I cannot test this at the moment...

2
fortrancharactertrim

2 Answers

18
votes

This

character (len=:), allocatable :: input_trim

is certainly syntactically correct in Fortran 2003. You don't say what the error that gfortran raises is, so I can't comment on why it doesn't accept the line -- perhaps you have an old version of the compiler installed.

With an up-to-date Fortran compiler (eg Intel Fortran v14.xxx) you don't need to allocate the character variable's size prior to assigning to it, you can simply write

input_trim = trim(input)

Note that 

read(*,*) input_trim

won't work.

0
votes

With Absoft Fortran, this compiles (haven't run with it yet):

character,dimension(:),allocatable::Line_for_IO !Metcalf,Reid,Cohen p. 107, w/mods
if(allocated(Line_for_IO)) deallocate(Line_for_IO)
allocate(Line_for_IO(7*n+40))