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Learn Red ? Fundamentals of Red

You're reading from   Learn Red ? Fundamentals of Red Get up and running with the Red language for full-stack development

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Product type Paperback
Published in May 2018
Publisher Packt
ISBN-13 9781789130706
Length 252 pages
Edition 1st Edition
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Author (1):
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Ivo Balbaert Ivo Balbaert
Author Profile Icon Ivo Balbaert
Ivo Balbaert
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Table of Contents (13) Chapters Close

Preface 1. Red's Mission FREE CHAPTER 2. Setting Up for Development 3. Using Words, Values, and Types 4. Code-Controlling Structures 5. Working with Series and Blocks 6. Using Functions and Objects 7. Working with Files 8. Parsing Data 9. Composing Visual Interfaces 10. Advanced Red 11. Assessments
12. Other Books You May Enjoy

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: 10
if 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 n 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 name or code.

Only use cause-error if you want to stop your program displaying the error message.

So to summarize...

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