Jonathan M Davis:
>Well, I would pount out that you mentioning it more or less reopens the
>discussion,<
You are right, but probably Walter will not sue me for reopening an old thread
;-)
In the things you are saying you seem to ignore the "goto" I have written two
times in my answers :-)
>An extension of that is if you have two cases which are almost identical but
>where one of them needs to do something first before the code that is common
>between both cases.<
You can write this C-style switch:
switch (x) {
case 0: foo();
case 1: bar();
}
As this (this is D syntax that you can already use):
void main() {
int x, y;
switch (x) {
case 0: y++; goto case 1;
case 1: y++;
default:
}
}
> A more complicated example would be one where you're doing something like
> Duff's Device:
>
> send(to, from, count)
> register short *to, *from;
> register count;
> {
> register n=(count+7)/8;
> switch(count%8){
> case 0: do{ *to = *from++;
> case 7: *to = *from++;
> case 6: *to = *from++;
> case 5: *to = *from++;
> case 4: *to = *from++;
> case 3: *to = *from++;
> case 2: *to = *from++;
> case 1: *to = *from++;
> }while(--n>0);
> }
> }
You can use gotos (this is a different function, it copies whole arrays, 'to'
too is incremented):
import std.stdio: writeln;
void arrryCopy(short* to, short* from, int count) {
foreach (_; 0 .. count / 8) {
*to++ = *from++; *to++ = *from++;
*to++ = *from++; *to++ = *from++;
*to++ = *from++; *to++ = *from++;
*to++ = *from++; *to++ = *from++;
}
final switch (count % 8) {
case 7: *to++ = *from++; goto case 6;
case 6: *to++ = *from++; goto case 5;
case 5: *to++ = *from++; goto case 4;
case 4: *to++ = *from++; goto case 3;
case 3: *to++ = *from++; goto case 2;
case 2: *to++ = *from++; goto case 1;
case 1: *to++ = *from++; break;
case 0: break;
}
}
void main() {
short[9] a1 = 1;
short[a1.length] a2;
writeln(a1, " ", a2);
arrryCopy(a2.ptr, a1.ptr, a1.length);
writeln(a1, " ", a2);
}
I have used the static switch to avoid the default case.
Using gotos like that is a bit less conventient than the C code, but I think it
can be acceptable.
> switch(value)
> {
> case 0:
> do something...
> case 1:
> do something else...
> case 2:
> do a third thing...
> case 3:
> do yet more...
> }
You can translate it as:
switch(value)
{
case 0:
do something...
goto case 1;
case 1:
do something else...
goto case 2;
case 2:
do a third thing...
goto case 3;
case 3:
do yet more...
break;
default:
...
}
Bye,
bearophile
