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Switch statements come in two main variants: a structured switch, as in Pascal, which takes exactly one branch, and an unstructured switch, as in C, which functions as a type of goto. The main reasons for using a switch include improving clarity, by reducing otherwise repetitive coding, and (if the heuristics permit) also offering the potential ...
The #switch function selects between multiple alternatives based on an input string. {{#switch: test string | case1 = value for case 1 | ... | default value}} Equivalent to the switch statement found in some programming languages, it is a convenient way of dealing with multiple cases without having to chain lots of #if functions together ...
With var, let, and const statements, only the declaration is hoisted; assignments are not hoisted. Thus a var x = 1 statement in the middle of the function is equivalent to a var x declaration statement at the top of the function, and an x = 1 assignment statement at that point in the middle of
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.
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.
switch (variable) { case case 1: instructions «break_or_jump_statement» ... «default: instructions break_or_jump_statement»} All non-empty cases must end with a break or goto case statement (that is, they are not allowed to fall-through to the next case). The default case is not required to come last.
Duff's device provides a compact loop unrolling by using the case keyword both inside and outside the loop. This is unusual because the contents of a case statement are traditionally thought of as a block of code nested inside the case statement, and a reader would typically expect it to end before the next case statement.
In such case it is always possible to use a function call, but this can be cumbersome and inelegant. For example, to pass conditionally different values as an argument for a constructor of a field or a base class, it is impossible to use a plain if-else statement; in this case we can use a conditional assignment expression, or a function call ...