Connection With Design By Contract
Command-query separation is particularly well suited to a design by contract (DbC) methodology, in which the design of a program is expressed as assertions embedded in the source code, describing the state of the program at certain critical times. In DbC, assertions are considered design annotations – not program logic – and as such, their execution should not affect the program state. CQS is beneficial to DbC because any value-returning method (any query) can be called by any assertion without fear of modifying program state.
In theoretical terms, this establishes a measure of sanity, whereby one can reason about a program's state without simultaneously modifying that state. In practical terms, CQS allows all assertion checks to be bypassed in a working system to improve its performance without inadvertently modifying its behaviour. CQS may also prevent the occurrence of certain kinds of heisenbugs.
Read more about this topic: Command-query Separation
Famous quotes containing the words connection with, connection, design and/or contract:
“Morality becomes hypocrisy if it means accepting mothers’ suffering or dying in connection with unwanted pregnancies and illegal abortions and unwanted children.”
—Gro Harlem Brundtland (b. 1939)
“The connection between dress and war is not far to seek; your finest clothes are those you wear as soldiers.”
—Virginia Woolf (1882–1941)
“With wonderful art he grinds into paint for his picture all his moods and experiences, so that all his forces may be brought to the encounter. Apparently writing without a particular design or responsibility, setting down his soliloquies from time to time, taking advantage of all his humors, when at length the hour comes to declare himself, he puts down in plain English, without quotation marks, what he, Thomas Carlyle, is ready to defend in the face of the world.”
—Henry David Thoreau (1817–1862)
“Any intelligent woman who reads the marriage contract and then goes into it, deserves all the consequences.”
—Isadora Duncan (1878–1927)