History and Etymology
Peter J. Landin defined the term closure in 1964 as having an environment part and a control part as used by his SECD machine for evaluating expressions. Joel Moses credits Landin with introducing the term closure to refer to a lambda expression whose open bindings (free variables) have been closed by (or bound in) the lexical environment, resulting in a closed expression, or closure. This usage was subsequently adopted by Sussman and Steele when they defined Scheme in 1975, and became widespread.
The term closure is often mistakenly used to mean anonymous function. This is probably because most languages implementing anonymous functions allow them to form closures and programmers are usually introduced to both concepts at the same time. An anonymous function can be seen as a function literal, while a closure is a function value. These are, however, distinct concepts. A closure retains a reference to the environment at the time it was created (for example, to the current value of a local variable in the enclosing scope) while a generic anonymous function need not do this.
Read more about this topic: Closure (computer Science)
Famous quotes containing the words history and, history and/or etymology:
“There is a constant in the average American imagination and taste, for which the past must be preserved and celebrated in full-scale authentic copy; a philosophy of immortality as duplication. It dominates the relation with the self, with the past, not infrequently with the present, always with History and, even, with the European tradition.”
—Umberto Eco (b. 1932)
“The thing that struck me forcefully was the feeling of great age about the place. Standing on that old parade ground, which is now a cricket field, I could feel the dead generations crowding me. Here was the oldest settlement of freedmen in the Western world, no doubt. Men who had thrown off the bands of slavery by their own courage and ingenuity. The courage and daring of the Maroons strike like a purple beam across the history of Jamaica.”
—Zora Neale Hurston (1891–1960)
“Semantically, taste is rich and confusing, its etymology as odd and interesting as that of “style.” But while style—deriving from the stylus or pointed rod which Roman scribes used to make marks on wax tablets—suggests activity, taste is more passive.... Etymologically, the word we use derives from the Old French, meaning touch or feel, a sense that is preserved in the current Italian word for a keyboard, tastiera.”
—Stephen Bayley, British historian, art critic. “Taste: The Story of an Idea,” Taste: The Secret Meaning of Things, Random House (1991)