Inside the switch statement

[BCS]

Hello Sam,

> To save time ,just get to my point:I do not understand why such code
> below inside the switch ... case statement is allowed ,what is the
> point of do ... while...:

This is a classic C thing. The short explanation is that a switch is a conditional, 
many way goto and the labels can be *anywhere* in the body (except inside 
another switch). For the more in depth version Google "duff's device".

> 
> This example uses a mixin to implement a generic Duff's device for an
> arbitrary statement (in this case, the arbitrary statement is in
> bold).

BTW: where is this from?

> A nested function is generated as well as a delegate literal,
> these can be inlined by the compiler:
> template duffs_device(alias id1, alias id2, alias s)
> {
> void duff_loop()
> {
> if (id1 < id2)
> {
> typeof(id1) n = (id2 - id1 + 7) / 8;
> switch ((id2 - id1) % 8)
> {
> case 0:        do {  s();
> case 7:              s();
> case 6:              s();
> case 5:              s();
> case 4:              s();
> case 3:              s();
> case 2:              s();
> case 1:              s();
> } while (--n > 0);
> }
> }
> }
> }
> void foo() { writefln("foo"); }
> 
> void test()
> {
> int i = 1;
> int j = 11;
> mixin duffs_device!(i, j, delegate { foo(); } );
> duff_loop();	// executes foo() 10 times
> }