Question

I want to create a dynamic variable name using Fortran.

The variable name will be obtained by concatenating a string and another string/integer. Then I want to use this variable name to store a value or another variable.

e.g.

! assign values to 2 variables

    my_string = h
    my_integer = 1

! perform concatenation resulting in the dynamic variable name,  h1


! Set the value of variable h1 to another integer value

    h1 = 5

Answer 1

I think you want to use a data structure. If you have pairs or groups of values that go together, then create a derived data type which can hold both. There’s an explanation on this page:

http://web.mse.uiuc.edu/courses/mse485/comp_info/derived.html

If you have a list of these pairs (like your string and int above), then you can create an array of these types. Example code below taken from the page linked above:

type mytype
   integer:: i
   real*8 :: a(3)
end type mytype

type (mytype) var

Array:

type (mytype) stuff(3)

var%i = 3
var%a(1) = 4.0d0
stuff(1)%a(2) = 8.0d0

An significant benefit of doing this is that you can pass the pairs/groups of items to functions/subroutines together. This is an important programming principle called Encapsulation, and is used extensively in the Object Oriented programming paradigm.