def-fwrapper

Macro

Package: excl

Arguments: name arglist &body body

Produces a form which returns name and defines an fwrapper as a side effect. This fwrapper is suitable for use as the fwrap-function in a call to fwrap.

name can be any function spec.

arglist is an ordinary lambda list. All ordinary lambda list keywords may be used, including &allow-other-keys, &aux, &key, &optional, and &rest. If either &key or &rest are present, then the arglist is automatically forced to be a list. (Note: the current implementation also forces a list when optional arguments are specified, because of some potential problems when a not-given optional argument is setq'd).

Argument accesses are provided for by means of symbol-macrolets, in a manner that is mostly intuitive. The arguments can simply be accessed by name, and they can be setq'd under most circumstances, with exceptions given below. The values of these setq'd arguments become part of the argument list that is sent to the next more inner fwrapper.

Exceptions:

If the &rest arg is setq'd, the change only takes place for the current fwrapper, and is not passed inward. However, any changes made to the structure of the rest arg (via (setf car) or (setf cdr) or similar functions) will result in a change that will be passed inward.
Any &key value that is setq'd will not replace or add the key value to the arglist that is passed inward, although the change will be in effect for the duration of the fwrapper.

See fwrappers-and-advice.htm for information of fwrapping functions (and on the older, deprecated advice facility).

The documentation is described in introduction.htm and the index is in index.htm.

Created 2000.10.5.