Derived Types and Allocatable

Allocatable in Derived Type

A derived type can hold an allocatable component, giving a bag-of-values with runtime size.

Program

Play the program to allocate and fill an inner array, then sum it.

allocatable_in_type.f90 
program allocatable_in_type_demo
    implicit none
    type :: bag
        integer, allocatable :: items(:)
    end type bag
    type(bag) :: b
    allocate(b%items(3))
    b%items = [5, 7, 9]
    print '(I0)', sum(b%items)
end program allocatable_in_type_demo
allocatable component `integer, allocatable :: items(:)` makes the component sized at run time.
allocate component `allocate(b%items(3))` allocates inside the instance.
array assign `b%items = [5, 7, 9]` fills the allocated array in one statement.