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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 ...
Duff realized that to handle cases where count is not divisible by eight, the assembly programmer's technique of jumping into the loop body could be implemented by interlacing the structures of a switch statement and a loop, putting the switch's case labels at the points of the loop body that correspond to the remainder of count/8: [1]
Examples of, and arguments for, Jump Tables via Function Pointer Arrays in C/C++ [3] Example code generated by 'Switch/Case' branch table in C, versus IF/ELSE. [4] Example code generated for array indexing if structure size is divisible by powers of 2 or otherwise.
Switch statements can allow compiler optimizations, such as lookup tables. In dynamic languages , the cases may not be limited to constant expressions, and might extend to pattern matching , as in the shell script example on the right, where the *) implements the default case as a glob matching any string.
C++14 allows the creation of variables that are templated. An example given in the proposal is a variable pi that can be read to get the value of pi for various types (e.g., 3 when read as an integral type; the closest value possible with float, double or long double precision when read as float, double or long double, respectively; etc.).
switch <uint32, int32, int32 (t1..tN)> Jump to one of n values. Base instruction 0xFE 0x14 tail. Subsequent call terminates current method. Prefix to instruction 0x7A throw: Throw an exception. Object model instruction 0xFE 0x12 unaligned. (alignment) Subsequent pointer instruction might be unaligned. Prefix to instruction 0x79 unbox <valuetype>
C++ compilers prohibit goto or switch from crossing an initialization, as in the following C99 code: void fn ( void ) { goto flack ; int i = 1 ; flack : ; } While syntactically valid, a longjmp() results in undefined behaviour in C++ if the jumped-over stack frames include objects with nontrivial destructors. [ 12 ]
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.