OpenEuphoria

Re: switch statement

• Posted by mattlewis (admin) Mar 26, 2009
• 1338 views

Actually, euphoria's switch can do Duff's device. Here's the Stroustroup version from Wikipedia:

dsend(to, from, count) 
char *to, *from; 
int count; 
{ 
    int 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); 
    } 
} 

Here's a euphoria version (used the print operator instead of poking to memory, but demonstrates the interesting part of the device):

rocedure dprint( atom To, atom from, integer count ) 
    integer n = floor( (count+7) / 8 ) 
    switch remainder( count, 8 ) do 
	case 0:  
	loop do 
		? To & from To += 1 from += 1 
	case 7: 
		? To & from To += 1 from += 1 
	case 6: 
		? To & from To += 1 from += 1 
	case 5: 
		? To & from To += 1 from += 1 
	case 4: 
		? To & from To += 1 from += 1 
	case 3: 
		? To & from To += 1 from += 1 
	case 2: 
		? To & from To += 1 from += 1 
	case 1: 
		? To & from To += 1 from += 1 
	 
	n -= 1 
	until n <= 0 
    end switch 
end procedure 

Yes, though it could be merely syntactic sugar. With a large enough range, though, you probably need to (want to?) change from a simple jump table. We've talked about doing such a thing for euphoria.

Matt

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