Contents
What do you need to know about the switch statement?
1 Switch statement. The switch statement allows you to provide a variable and a list of possible values. 2 Parameters. A unique feature of the PowerShell switch is that it has a number of switch parameters that change how it performs. 3 Advanced details. 4 Other patterns. 5 Final words.
When does a break statement exit the switch?
A break statement exits the switch. This is the same behavior that continue presents for single values. The difference is shown when processing an array. break stops all processing in the switch and continue moves onto the next item. In this case, if we hit any lines that start with Error then we get an error and the switch stops.
How is a switch statement implemented in a compiler?
The first thing I discovered is that compilers typically have a number of ways of implementing a switch statement. They seem to be loosely divided into the following trichotomy: An if-else-if-else-if chain. In this implementation, the switch statement is treated as syntactic sugar for an if-else-if chain.
What happens to the execution time of a switch statement?
This simple change can cause the compiler to completely change the implementation of the switch statement. As a result, you may find that: The worst case execution time has jumped dramatically. The mean execution time has jumped dramatically.
How many case labels are in a switch statement?
Let’s start by looking at a very simple switch statement. It has six case labels, does not have a default case, and has no fall-trough cases so each case is followed by a break statement: It would be logical to assume that the above code would be translated into a jump table.
How to reduce switch statement down to machine code?
The first step is to remove a single label from the switch, effectively reducing a number of case labels to five. By doing so, nothing has changed regarding how compilers handle switch statement in case with both GCC and Clang compilers. Reducing a number of cases further results in some interesting changes.
Which is executed faster switch statement or IF THEN ELSE?
Therefore, the code generated from switch expressions is executed faster than if-then-else. Compilers generate a binary lookup table to match the input value when using switch statement.