filter

n 1: removes something from whatever passes through it

2: alters the frequency spectrum of signals passing through it

v 1: remove by passing through a filter; "filter out the

impurities" [syn: {filtrate}, {strain}, {separate out},

{filter out}]

2: pass through; "Water permeated sand easily" [syn: {percolate},

{sink in}, {permeate}]

3: run or flow slowly, or in an unsteady stream: "reports began

to dribble in." [syn: {trickle}, {dribble}]

filter

1. (Originally {Unix}, now also {MS-DOS}) A program that

processes an input data stream into an output data stream in

some well-defined way, and does no I/O to anywhere else except

possibly on error conditions; one designed to be used as a

stage in a {pipeline} (see {plumbing}). Compare {sponge}.

2. ({functional programming}) A {higher-order function} which

takes a {predicate} and a list and returns those elements of

the list for which the predicate is true. In {Haskell}:

filter p [] ◦ []

filter p (x:xs) ◦ if p x then x : rest else rest

where

rest ◦ filter p xs

See also {filter promotion}.

[{Jargon File}]