Expression (computer science): Difference between revisions

Revision as of 15:23, 20 January 2021

Revision as of 13:28, 2 April 2021

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In simple settings, the [[return type|resulting value]] is usually one of various [[primitive data type|primitive types]], such as numerical, [[string (computer science)|string]], [[boolean expression|boolean]], [[complex data type]] or other types.

Expression is often contrasted with [[Statement (computer science)|statement]] - a—a syntactic entity, whichthat has no value (an instruction.).

==Examples==

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Note that the formal notion of a side effect is a change to the abstract state of the running program.

Another class of side effects are changes to the concrete state of the computational system, such as loading data into cache memories. Languages whichthat are often described as "side effect–free" will generally still have concrete side effects whichthat can be exploited, for example, in [[side-channel attack]]s.

Furthermore, the elapsed time evaluating an expression (even one with no other apparent side effects), is sometimes essential to the correct operation of a system, as behaviour in time is easily visible from outside the evaluation environment by other parts of the system with which it interacts, and might even be regarded as the ''primary'' effect such as when performing [[Benchmark (computing)|benchmark testing]].