Module Coding Rules

All new code is to be placed in Fortran 90 modules to enforce strong type-checking and to facilitate encapsulation. A module is built around its data, but it also contains the procedures accessing this data, particularly the procedures creating, destroying, or modifying this data. Of course procedures will often access data in several modules, so there is sometimes ambiguity as to where they belong. In this case it is often useful to place them in steering modules.

Module names will look like (root_mod, and routines in it will often contain (root in their names. When a module is compiled, two files are produced, with extensions .o and .mod. The .mod file contains the variable and procedure type definitions, and is used in the compilation stage of other use associated modules to enforce type cosistency. These files are all placed in a separate /module subdirectory, much like include files. Contents of a typical module are (in order):

USE statements

List module names containing data or procedures accessed in this module.

PRIVATE

Make variables inaccessible by default.

PUBLIC names

List of variables and procedures to be made accessible through use association. If the module contains only public names and has no USE statements then PRIVATE and PUBLIC can be omitted.

IMPLICIT NONE

TYPE, INTEGER, REAL, INTERFACE

Data type definitions, definitions of variables global to the module, interface blocks. For consistency between modules the interface block code will be put in a .ifb file and included by the cpp preprocesser.

CONTAINS

Followed by code for procedures.