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)

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/
*** Script Error: cannot compare 4 with "abc"
*** Where: <

This occurs when comparing...