Machining program editing assist device

A numerical controller that assists generation of a machining program for a workpiece after a change based on CAD data for the workpiece after the change and a machining program for the workpiece before the change, the numerical controller comprising:

• a memory;
• and
• a processor, wherein the processor is configured to:
• analyze the CAD data for the workpiece after the change and obtains CAD shape information which is shape information on the workpiece after the change;
• analyze a machining program before the change and obtains machining shape information which is shape information on the workpiece before the change;
• obtain predicted shape information by performing shape matching between the CAD shape information which is shape information on the workpiece after the change and the machining shape information which is shape information on the workpiece before the change, and specifying a changed shape;
• and
• insert, based on the predicted shape information which is shape information on the workpiece after the change, a machining path existing only in the CAD data which is shape information on the workpiece after the change into the machining program, and delete a machining path existing only in the machining program before the change from the machining program, thereby auto-generating a numerical controller program.