Syntax: error message

Returns an error with the given message and an error code of NONE. The error may be caught using the catch command.

proc myproc {x} {
    if {$x < 0} {
        error "input must be non-negative"
    }
    ...
}

In standard TCL, the error also has optional errorInfo and errorCode arguments. These are used in older TCL code to rethrow errors without polluting the stack trace. Modern TCL code uses the throw command to throw an error with an error code and the return command to rethrow an error (see the reference page for an example). Consequently, Molt doesn't implement these arguments.