use tries and catches and throwing error descriptive messages copiously so that when something goes wrong you can give the user descriptive, actually helpful error messages, you know -- like how windows doesn't. an error message should show descriptions for the whole hierarchy of exceptions raised. this way the user knows what he did wrong and can avoid it, and maybe can better aid the developer in knowing what he did wrong to cause that error.

also the application can continue on running after hte error is encountered. the user can choose to stop running it if it's not working well enough.

this should include segfaults and divide by zero and such.

this methodology could also be used for error messages or other prohibihitions that aren't generated by bugs but intentionally in response to user input.

also useful would be to show a traceback using a symbol table so the user can see what functions were called, and it can be an extended symbol table so that it actually includes useful descriptions of functions and maybe their parameters.