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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

Creating and catching errors

In a situation where you know a runtime error could occur, you can invoke a specific error yourself by using cause-error. For example:

m: 10if n = 0 [ cause-error 'math 'zero-divide [] ]print m / n

This line generates a *** Math Error: attempt to divide by zero when n is 0. This could be useful when entering a function with an n parameter that could be 0, and when we want to divide by  in the function.

Note that it needs the literal words 'math and 'zero-divide, describing the error's type and name; the third argument is a parameter block, which can be empty. Instead of cause-error, you can also encounter make error! [math zero-divide] or even make error! 400. They all do the same—generate the error with that ...

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Publisher Resources

ISBN: 9781789130706Supplemental Content