In homological algebra, an exact functor is a functor that preserves exact sequences. Exact functors are convenient for algebraic calculations because they can be more directly applied to presentations of objects. Much of the work in homological algebra is designed to cope with functors that fail to be exact, but in ways that can still be controlled.
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Famous quotes containing the word exact:
“He who asks fortune-tellers the future unwittingly forfeits an inner intimation of coming events that is a thousand times more exact than anything they may say. He is impelled by inertia, rather than curiosity, and nothing is more unlike the submissive apathy with which he hears his fate revealed than the alert dexterity with which the man of courage lays hands on the future.”
—Walter Benjamin (1892–1940)