closure


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closure

1. Politics (in a deliberative body) a procedure by which debate may be halted and an immediate vote taken
2. Geology the vertical distance between the crest of an anticline and the lowest contour that surrounds it
3. Logic the closed sentence formed from a given open sentence by prefixing universal or existential quantifiers to bind all its free variables
4. Maths the smallest closed set containing a given set
5. Psychol the tendency, first noted by Gestalt psychologists, to see an incomplete figure like a circle with a gap in it as more complete than it is

closure

[′klō·zhər]
(civil engineering)
(geology)
The vertical distance between the highest and lowest point on an anticline which is enclosed by contour lines.
(mathematics)
The union of a set and its cluster points; the smallest closed set containing the set.
Property of a mathematical set such that a specified mathematical operation that is applied to elements of the set produces only elements of the same set

closure

(programming)
In a reduction system, a closure is a data structure that holds an expression and an environment of variable bindings in which that expression is to be evaluated. The variables may be local or global. Closures are used to represent unevaluated expressions when implementing functional programming languages with lazy evaluation. In a real implementation, both expression and environment are represented by pointers.

A suspension is a closure which includes a flag to say whether or not it has been evaluated. The term "thunk" has come to be synonymous with "closure" but originated outside functional programming.

closure

(theory)
In domain theory, given a partially ordered set, D and a subset, X of D, the upward closure of X in D is the union over all x in X of the sets of all d in D such that x <= d. Thus the upward closure of X in D contains the elements of X and any greater element of D. A set is "upward closed" if it is the same as its upward closure, i.e. any d greater than an element is also an element. The downward closure (or "left closure") is similar but with d <= x. A downward closed set is one for which any d less than an element is also an element.

("<=" is written in LaTeX as \subseteq and the upward closure of X in D is written \uparrow_\D X).
References in periodicals archive ?
Increase in consumption of nonalcoholic beverages such as bottled water and carbonated soft drinks acts as a driving force for the growth of the market for plastic screw closures in Brazil.
It is the greater flexibility of plastics to adapt to the changing demands of the closure market that give them their on-going advantage.
Closure of the nasal cavities in the treatment of refractory hereditary haemorrhagic telangiectasia.
The Prince Albert pulp and paper mill in Saskatchewan, announced in October as an indefinite closure.
Zippered front closure, reinforced with hook-and-pile which provides a smooth surface when worn with OTV
After Defense Secretary Donald Rumsfeld on May 16 issues his recommendation for which bases to close, a base realignment and closure commission - or BRAC - will hold hearings through the summer.
Several research teams have planned clinical trials that, within 2 years, could show whether PFO closure works against migraines.
Rexam Closures & Containers, Evansville, IN, has introduced several closures that pass the new CPSC regulation for packaging products containing hydrocarbons, such as baby oils, paints, shoe polishes and car waxes.
If an owner or operator has shut down its UST, either temporarily or permanently, or desires to shut it down before the end of the year, such closure must comply with the requirements set forth in the federal regulations.
Among the obligations that would be covered by the proposed statement are decommissioning of nuclear facilities; dismantlement and removal of offshore oil and gas production facilities; closure, reclamation and removal of mining facilities; and closure and postclosure of landfills and certain hazardous waste storage facilities.
The purpose of having the soft bulb is to permit a closure without a great deal of effort but one that seals against water, outside materials or wind noise.