thunk
thunk: /thuhnk/ n. 1. [obs.]"A piece of coding which provides
an address", according to P. Z. Ingerman, who invented thunks in
1961 as a way of binding actual parameters to their formal
definitions in Algol-60 procedure calls. If a procedure is called
with an expression in the place of a formal parameter, the compiler
generates a thunk which computes the expression and leaves the
address of the result in some standard location. 2. Later
generalized into: an expression, frozen together with its
environment, for later evaluation if and when needed (similar to
what in techspeak is called a `closure'). The process of unfreezing
these thunks is called `forcing'. 3. A stubroutine, in an overlay
programming environment, that loads and jumps to the correct
overlay. Compare trampoline. 4. People and activities scheduled
in a thunklike manner. "It occurred to me the other day that I am
rather accurately modeled by a thunk -- I frequently need to be
forced to completion." -- paraphrased from a plan file.
Historical note: There are a couple of onomatopoeic myths
circulating about the origin of this term. The most common is that
it is the sound made by data hitting the stack; another holds that
the sound is that of the data hitting an accumulator. Yet another
suggests that it is the sound of the expression being unfrozen at
argument-evaluation time. In fact, according to the inventors, it
was coined after they realized (in the wee hours after hours of
discussion) that the type of an argument in Algol-60 could be
figured out in advance with a little compile-time thought,
simplifying the evaluation machinery. In other words, it had
`already been thought of'; thus it was christened a `thunk', which
is "the past tense of `think' at two in the morning".
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