Chapters:   1: Introduction   2: Simple example   3: Invocation   4: Finer Control   5: X-Y Plots   6: Contour Plots   7: Image Plots   8: Examples   9: Gri Commands   10: Programming   11: Environment   12: Emacs Mode   13: History   14: Installation   15: Gri Bugs   16: Test Suite   17: Gri in Press   18: Acknowledgments   19: License Indices:   Concepts   Commands   Variables

10: Programming in the Gri Language The Gri programming language has `if' statements to control program flow, and a `while' statement to repeat commands. There are two data types in Gri: ``variables'' (to store numbers) and ``synonyms'' (to store character strings). Gri recognizes commands by matching statements against its list of known commands. This list is extensible; it is easy to add new commands as extensions to Gri. Defaults: How Gri normally acts Online Help: Getting help from gri itself Long Command Lines: Continued lines Variables: Variables (for storing numbers) Synonyms: Synonyms (for storing character strings) If Statements: If statements Loops: Repeating command lines Mathematics: Doing mathematics on columns, grids etc rpn Mathematics: Doing mathematics on variables Text: Doing things with characters strings Adding New Commands: How to customize Gri by adding new commands Missing Values: How to specify missing data Hints: Hints for good Gri programming Debugging: Debugging Gri programs Error Messages: What to do about Gri error messages Missing Values: Missing value code Operating System: Using Gri in OS and OS in Gri Resource File: Personalizing Gri