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.

