Update: This got fixed in C# 7.0 with pattern matching switch (MyObj) case Type1 t1: case Type2 t2: case Type3 t3: Old answer: It is a hole in C#’s game, no silver bullet yet. You should google on the ‘visitor pattern’ but it might be a little heavy for you but still something you should … Read more
switch ($value) { case 1: case 2: echo “the value is either 1 or 2.”; break; } This is called “falling through” the case block. The term exists in most languages implementing a switch statement.
SWITCH statement only produces same assembly as IFs in debug or compatibility mode. In release, it will be compiled into jump table (through MSIL ‘switch’ statement)- which is O(1). C# (unlike many other languages) also allows to switch on string constants – and this works a bit differently. It’s obviously not practical to build jump … Read more
This is was not possible with a switch statement in Java until Java 18. You had to check for null before the switch. But now, with pattern matching, this is a thing of the past. Have a look at JEP 420: Pattern matching and null Traditionally, switch statements and expressions throw NullPointerException if the selector … Read more
You absolutely can use is in a switch block. See “Type Casting for Any and AnyObject” in the Swift Programming Language (though it’s not limited to Any of course). They have an extensive example: for thing in things { switch thing { case 0 as Int: println(“zero as an Int”) case 0 as Double: println(“zero … Read more
A break will allow you continue processing in the function. Just returning out of the switch is fine if that’s all you want to do in the function.
There are several optimizations a compiler can make on a switch. I don’t think the oft-mentioned “jump-table” is a very useful one though, as it only works when the input can be bounded some way. C Pseudocode for a “jump table” would be something like this — note that the compiler in practice would need … Read more
As pointed out by the other answer, because the case values are contiguous (as opposed to sparse), the generated bytecode for your various tests uses a switch table (bytecode instruction tableswitch). However, once the JIT starts its job and compiles the bytecode into assembly, the tableswitch instruction does not always result in an array of … Read more
The reason why has to do with the type system. C/C++ doesn’t really support strings as a type. It does support the idea of a constant char array but it doesn’t really fully understand the notion of a string. In order to generate the code for a switch statement the compiler must understand what it … Read more
The problem is that variables declared in one case are still visible in the subsequent cases unless an explicit { } block is used, but they will not be initialized because the initialization code belongs to another case. In the following code, if foo equals 1, everything is ok, but if it equals 2, we’ll accidentally … Read more