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Simon Tatham's coroutines in C utilizes the same switch/case trick; Adam Dunkels's Protothreads - Lightweight, Stackless Threads in C also uses nested switch/case statements (see also The lightest lightweight threads, Protothreads) Pigeon's device is a related technique: intertwined switch/case and if/else statements
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 ...
Switch statements (or case statements, or multiway branches) compare a given value with specified constants and take action according to the first constant to match. There is usually a provision for a default action ("else", "otherwise") to be taken if no match succeeds. Switch statements can allow compiler optimizations, such as lookup tables.
Multiway branch is the change to a program's control flow based upon a value matching a selected criteria. It is a form of conditional statement.A multiway branch is often the most efficient method of passing control to one of a set of program labels, especially if an index has been created beforehand from the raw data.
The switch parser function, coded as "#switch", selects the first matching branch in a list of choices, acting as a case statement. Each branch can be a value , an expression ( calculation ), or a template call, [ 1 ] evaluated and compared to match the value of the switch.
For example, one can write a fully recursive-nestable SWITCH–CASE–DEFAULT–ENDSWITCH statement using this macro facility. Because of the HLA macro facilities context-free design, these switch..case..default..endswitch statements can be nested, and the nested statements' emitted code will not conflict with the outside statements.
Examples of, and arguments for, Jump Tables via Function Pointer Arrays in C/C++; Example code generated by 'Switch/Case' branch table in C, versus IF/ELSE. Example code generated for array indexing if structure size is divisible by powers of 2 or otherwise. "Arrays of Pointers to Functions" by Nigel Jones
In the simple case, the loop control is merely an administrative overhead that arranges the productive statements. The loop itself contributes nothing to the results desired, merely saving the programmer the tedium of replicating the code a hundred times which could have been done by a pre-processor generating the replications, or a text editor.