Attempt - Function Summary

Summary:

Tries to evaluate and returns result or NONE on error.

Usage:

attempt value

Arguments:

value - The value argument.

Description:

The ATTEMPT function is a shortcut for the frequent case of:

error? try [block]

The format for ATTEMPT is:

attempt [block]

ATTEMPT is useful where you either do not care about the error result or you want to make simple types of decisions based on the error.

attempt [make-dir %fred]

ATTEMPT returns the result of the block if an error did not occur. If an error did occur, a NONE is returned.

In the line:

value: attempt [load %data] probe value none

the value is set to NONE if the %data file cannot be loaded (e.g. it is missing or contains an error). This allows you to write conditional code such as:

if not value: attempt [load %data] [print "Problem"] Problem

Or code such as:

value: any [attempt [load %data] [12 34]] probe value [12 34]

Related:

error? - Returns TRUE for error values.
try - Tries to DO a block and returns its value or an error.