REBOL 3 Concepts: Errors

Overview

Errors are exceptions that occur when certain irregular conditions occur. These conditions range from syntax errors to file or network access errors. Here are a few examples:

12-30
** Syntax error: invalid "date" -- "12-30"
** Near: (line 1) 12-30

1 / 0
** Math error: attempt to divide by zero
** Where: /
** Near: / 0

read %nofile.r
** Access error: cannot open: %nofile.r reason: -3
** Where: read
** Near: read %nofile.r

Errors are processed within the system as values of the error! datatype. An error is an object that, if evaluated, will print an error message and halt. You can also catch errors and handle them in your script. Errors can be passed to functions, returned from functions, and assigned to variables.