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In the C programming language, Duff's device is a way of manually implementing loop unrolling by interleaving two syntactic constructs of C: the do-while loop and a switch statement. Its discovery is credited to Tom Duff in November 1983, when Duff was working for Lucasfilm and used it to speed up a real-time animation program.
Switch statements function somewhat similarly to the if statement used in programming languages like C/C++, C#, Visual Basic .NET, Java and exist in most high-level imperative programming languages such as Pascal, Ada, C/C++, C#, [1]: 374–375 Visual Basic .NET, Java, [2]: 157–167 and in many other types of language, using such keywords as ...
Within an imperative programming language, a control flow statement is a statement that results in a choice being made as to which of two or more paths to follow. For non-strict functional languages, functions and language constructs exist to achieve the same result, but they are usually not termed control flow statements.
It is possible to introduce generators into C++ using pre-processor macros. The resulting code might have aspects that are very different from native C++, but the generator syntax can be very uncluttered. [11] The set of pre-processor macros defined in this source allow generators defined with the syntax as in the following example:
The loop-switch sequence is a specific derivative of spaghetti code. It is not necessarily an antipattern to use a switch statement within a loop—it is only considered incorrect when used to model a known sequence of steps. The most common example of the correct use of a switch within a loop is an inversion of control such as
reduced source statements (versus repetitive If statements) reduced requirement to test return codes individually (if used at call site to determine subsequent program flow) Algorithmic and code efficiency (data need only be encoded once and branch table code is usually compact), and the potential to attain high data compression ratios. For ...
However, for many uses of the switch statement in real code, it is possible to avoid branching altogether and replace the switch with one or more table look-ups. For example, the Has30Days example [presented earlier] can be implemented as the following:[C example]" "A Superoptimizer Analysis of Multiway Branch Code Generation" by Roger Anthony ...
A control table can be constructed along similar lines to a language dependent switch statement but with the added possibility of testing for combinations of input values (using boolean style AND/OR conditions) and potentially calling multiple subroutines (instead of just a single set of values and 'branch to' program labels). (The switch ...