error — Raise an error

$\begin{rail} Error : 'error' '(' ( () \vert String) ')' ; \end{rail}$
The error function allows user defined functions to jump back to the prompt when they detect an error has occurred. The nature of the error message displayed is up to the user. If no argument is supplied, error will print the default message, which is USER-RAISED-ERROR. If a string arguments is supplied, then that string is displayed. Jumping back to the prompt means execution of the current loop or function is terminated immediately, and the control is returned to the command line.

Subsections

- - Example