The equate expression language is a reasonably powerful but simple language designed solely for data manipulation within the GRG file. It has a very limited file i/o capability and no system i/o. It has conditions and loops, local variables, system (global) variables, support for record searching and matching in database files, basic maths, logical and relational operators, function call support (with arguments), and five interchangeable data types. The language is designed to supplement the text bodies, and equates can be called from text bodies (like user defined macros) to insert text that requires more complex processing to generate. They are often used to build things like summary tables from database files which are not so easy to generate directly using predefined and user defined macros.
Equates are automatically converted to a reversed equate which is a lower level interpreted langauge which can also be used directly if preferred (see section Reversed Equate Expressions).
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