recover               package:methods               R Documentation

Browsing on an Error

Description:

     This function allows the user to browse directly on any of the
     currently active function calls, and is suitable as an error
     option. The expression `options(error=recover)' will make this the
     error option.

Usage:

     recover()

Details:

     When called, `recover' prints the list of current calls, and
     prompts the user to select one of them.  The standard R `browser'
     is then invoked from the corresponding environment; the user can
     type ordinary S language expressions to be evaluated in that
     environment.

     When finished browsing in this call, type `c' to return to
     `recover' from the browser.  Type another frame number to browse
     some more, or type `0' to exit `recover'.

     WARNING: Do not use the special `Q' command to go directly from
     the browser to the prompt level of the evaluator.  This currently
     interacts with `recover' to effectively turn off the error option
     for the next error (on subsequent errors, `recover' will be called
     normally)

Value:

     Nothing useful is returned.  However, you can invoke `recover'
     directly from a function, rather than through the error option
     shown the usage section.  In this case, execution continues after
     you type `0' to exit `recover'.

Compatibility Note:

     The R `recover' function can be used in the same way as the S-Plus
     function of the same name; therefore, the error option shown is a
     compatible way to specify the error action.  However, the actual
     functions are essentially unrelated and interact quite differently
     with the user.

References:

     Programming with Data, (John M. Chambers, Springer, 1998).  See
     the compatibility note above, however.

See Also:

     See `dump.frames' and `debugger' for the more traditional approach
     to error recovery.

