snap (redirected from press stud)

snap

1. Informal See snapshot

2. Brit a card game in which the word snap is called when two cards of equal value are turned up on the separate piles dealt by each player

3. American football the start of each play when the centre passes the ball back from the line of scrimmage to a teammate

---

1.	(language)	SNAP - 1. An 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].
2.		snap - 1. To remove indirection, e.g. by replacing a pointer to a pointer with a pointer to the final target (see chase pointers). The underlying metaphor may be a rubber band stretched through a number of points; if you release it from the intermediate points, it snaps to a straight line from first to last. Often a trampoline performs an error check once and then snaps the pointer that invoked it so subsequent calls will 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.