Book Image

Learn Red ? Fundamentals of Red

By : Ivo Balbaert
Book Image

Learn Red ? Fundamentals of Red

By: Ivo Balbaert

Overview of this book

A key problem of software development today is software bloat, where huge toolchains and development environments are needed in software coding and deployment. Red significantly reduces this bloat by offering a minimalist but complete toolchain. This is the first introductory book about it, and it will get you up and running with Red as quickly as possible. This book shows you how to write effective functions, reduce code redundancies, and improve code reuse. It will be helpful for new programmers who are starting out with Red to explore its wide and ever-growing package ecosystem and also for experienced developers who want to add Red to their skill set. The book presents the fundamentals of programming in Red and in-depth informative examples using a step-by-step approach. You will be taken through concepts and examples such as doing simple metaprogramming, functions, collections, GUI applications, and more. By the end of the book, you will be fully equipped to start your own projects in Red.
Table of Contents (13 chapters)
11
Assessments

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...