Container library for Fortran programming language
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qContainers is a container library for Fortran language. It enables to store any internal Fortran data type and any derived data type to the container. The library wraps a subset of containers from qLibc library for C language and one container (set) from c-algorithms library.

Following containers are implemented currently:

  • Containers for Key/Value pairs
    • Tree Table (qtreetbl) --- in binary tree (left-leaning red-black tree) data structure.
    • Hash Table (qhashtbl) --- in hash-based data structure.
  • Containers for Objects
    • List (qlist) --- doubly linked list.
    • Vector (qvector) --- growable array of elements.
    • Set (qset) --- collection of unique values.

The library uses some features of Fortran 2003 and TS-29113, therefore a relatively new compiler version is required. Assumed-type dummy arguments or compiler directives in the case the compiler doesn't support assumed-type variables are used to enable store of any type to the containers. The containers were tested with Gfortran, Intel, PGI and Oracle Fortran compilers.


qContainers is published under 2-clause BSD license known as Simplified BSD License. Please refer the LICENSE.txt document included in the repository for more details.


All container APIs have a consistent look and feel. Type-bound procedures are used to make the use of the containers more convenient.

An example below illustrates how it looks like.

    subroutine colors()
        use qtreetbl_m
        implicit none

        type(qtreetbl_t) :: col
        integer :: val(3)
        integer :: ret_val(3)
        integer :: ns
        logical :: found

        ! Determine the size in bytes we need to save
        ! ns is a number of bytes for 3 integers
        ns = storage_size(val) / 8 * size(val)

        ! Create a new tree-table
        call col%new(ns)
        ! Put some values
        val = [255, 0, 0]
        call col%put("red", val(1)) ! ns bytes from val is copied
        val = [0, 255, 0]
        call col%put("green", val(1))

        ! Retrieve value
        call col%get("red", ret_val(1), found)
        print *, "red color = ", ret_val
    end subroutine


Read file.


An introduction tutorial can be found in docs folder. Also, the library has rather extensive test-cases from which users can learn how to use the library.


You can contribute to this project by reporting bugs, suggesting new features, implementing new features/containers, writing documentation/tutorial or simply by spreading the word about it.