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Learn Red ? Fundamentals of Red
book

Learn Red ? Fundamentals of Red

by Ivo Balbaert
May 2018
Beginner content levelBeginner
252 pages
6h 19m
English
Packt Publishing
Content preview from Learn Red ? Fundamentals of Red

Handling errors

Errors can be caused by wrong input from the user or they can be produced by the system.

If you enter 4 / 0 in the REPL, you will get a *** Math Error: attempt to divide by zero alert. The Red console does not crash in the case of an error, but a compiled program will.

The different types of predefined errors can be found with ? system/catalog/errors. To see the specific errors, use the type as a refinement—for example, ? system/catalog/errors/syntax, which shows, for example, a no-header, missing, or invalid error.

Now, let's return to our guessing game. What happens if the user enters a string such as "abc" instead of a number? Then the guessing stops right there—the program crashes with the error:

;-- see Chapter04/handling-errors.red: ...
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Publisher Resources

ISBN: 9781789130706Supplemental Content