SNAP

1. Early (IBM 360?) interpreted text-processing language for

beginners, close to basic English. ["Computer Programming in

English", M.P. Barnett, Harcourt Brace 1969].

2. ["Some Proposals for SNAP, A Language with Formal Macro

Facilities", R.B. Napper, Computer J 10(3):231-243 (1967)].

[same as 1?]

3. 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 behaviour 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.

[Jargon File]