Structure of the source file

The Mosel compiler may compile both models and packages source files. Once compiled, a model is ready for execution but a package is intended to be used by a model or another package (see Section The compiler directives).

The general structure of a model source file is as follows:

The model statement marks the beginning the program and the statement end-model its end. Any text following this instruction is ignored (this can be used for adding plain text comments after the end of the program). The model name may be any quoted string or identifier, this name will be used as the model name in the Mosel model manager. An optional set of directives and a parameters block may follow. The actual program/model is described in the body of the source file which consists of a succession of declaration blocks, subroutine definitions and statements.

The structure of a package (see Section Packages) source file is similar to the one of a model:

The package statement marks the beginning the library and the statement end-package its end. The package name must be a valid identifier.

It is important to understand that the language is procedural and not declarative: the declarations and statements are compiled and executed in the order of their appearance. As a consequence, it is not possible to refer to an identifier that is declared later in the source file or consider that a statement located later in the source file has already been executed. Moreover, the language is compiled and not interpreted: the entire source file is first translated — as a whole — into a binary form (the BIM file), then this binary form of the program is read again to be executed. During the compilation, except for some simple constant expressions, no action is actually performed. This is why only some errors can be detected during the compilation time, any others being detected when running the program.