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snap
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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.
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