Functions and procedures

When programs grow larger than the small examples presented so far, it becomes necessary to introduce some structure that makes them easier to read and to maintain. Usually, this is done by dividing the tasks that have to be executed into subtasks which may again be subdivided, and indicating the order in which these subtasks have to be executed and which are their activation conditions. To facilitate this structured approach, Mosel provides the concept of subroutines. Using subroutines, longer and more complex programs can be broken down into smaller subtasks that are easier to understand and to work with. Subroutines may be employed in the form of procedures or functions. Procedures are called as a program statement, they have no return value, functions must be called in an expression that uses their return value.

Mosel provides a set of predefined subroutines (for a comprehensive documentation the reader is referred to the Mosel Reference Manual), and it is possible to define new functions and procedures according to the needs of a specific program. A procedure that has occured repeatedly in this document is writeln. Typical examples of functions are mathematical functions like abs, floor, ln, sin etc.