snap v.
To replace a pointer to a pointer with a direct pointer; to
replace an old address with the forwarding address found there.
If you telephone the main number for an institution and ask for a
particular person by name, the operator may tell you that
person's extension before connecting you, in the hopes that you
will `snap your pointer' and dial direct next time. The
underlying metaphor may be that of a rubber band stretched
through a number of intermediate points; if you remove all the
thumbtacks in the middle, it snaps into a straight line from
first to last. See chase
pointers.
Often, the behavior of a trampoline is to perform an error check
once and then snap the pointer that invoked it so as henceforth
to bypass the trampoline (and its one-shot error check). In this
context one also speaks of `snapping links'. For example, in a
LISP implementation, a function interface trampoline might check
to make sure that the caller is passing the correct number of
arguments; if it is, and if the caller and the callee are both
compiled, then snapping the link allows that particular path to
use a direct procedure-call instruction with no further
overhead.