Expression How-To Guides

How-to guides explain how to solve common Expr tasks in PlanetCNC.

Use these pages when you already know the basic language syntax and want practical guidance for a specific job.

• Do basic calculations
• Use variables
• Use text values
• Use if and else
• Repeat code with loops
• Use functions
• Use callbacks
• Use timers safely
• Create custom dialogs
• Handle dialog results
• Run Python from Expr
• Show output and debug scripts
• Handle missing and invalid values
• Work with arrays and maps
• Use include files
• Use sessions safely
• Use classes in include files
• Use classes to keep data together
• Organize include files
• How relative paths work

• Tutorials teach Expr step by step.
• Reference Manual defines exact syntax and behavior.
• Cookbook contains complete examples to copy and adapt.