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September 11, 2000 17:12Subject:

Re: RFC 207 (v1) Array: Efficient Array LoopsMessage ID:

001d01c01c4d$89356010$0b00a8c0@optimaldecisions.comBuddha Buck wrote: > > Reading through the examples left me wondering about some > > technicalities: > > > > > @t[|i;|j] = @a[|j;|i]; # transpose 2-d @a > > > > Written like this it would require that @a is exact 2-dim, i.e. it would > > not just swap the first two dims of any n-dim array? I suppose if I'd > > want that I'd write > > > > @t[|i;|j;] = @a[|j;|i;]; # trailing ';' implies there might be > > trailing dims > > I will confess, operations on general multidimensional arrays were not > something I had considered when I originally had this idea. The > problem I see with your @t[|i;|j;] example is that it isn't clear that > the trailing dims for @a and @t will have tied iterators. I.e., if @a > is defined with "my @a :bounds (3,3,3);", which of these two should be > considered equivilant? > > @t[|i;|j;|k] = @a[|j;|i;|k]; # or... > @t[|i;|j;|k] = @a[|j;|i;|l]; > > Arguments could be made for either one. As I mentioned earlier, the trailling ';' is unnecessary. The reason why (all premises taken directly from the array RFCs: ---- LOLs and multidimensional arrays share all syntax. $a[$i] and $a[[$i]] are equivalent, except that [[]] automatically dereferences. Therefore: my @a = (1,2); $a[1] == 2; $a[[1]] == 2; my @b = ([1,2],[3,4]); $b[1] == [3,4]; @b[[1]] == (3,4); $a[[$i, $j]] is equivalent to $a[$i][$j]. @t[|i;|j] = @a[|j;|i] is equivalent to: foreach $i (@a) { foreach $j (@$i) { $t[$j][$i] = $a[$i][$j]; } } Regardless of whether $a[$i][$j] is a list ref, or a scalar, this loop will work just fine. The innermost dimensions of a 3d array are (semantically) list refs. Therefore the implicit loop works on 3d arrays. ---- The key to making this implicit loop syntax work is to consistantly apply the semantics about the loop that is being created. I like Buddha's proposal that the width of the generated loop is the smallest sub-expression that contains all of the iteration variables.Thread Previous | Thread Next

- RFC 207 (v1) Array: Efficient Array Loops by Perl6 RFC Librarian
- Re: RFC 207 (v1) Array: Efficient Array Loops by Buddha Buck
- Re: RFC 207 (v1) Array: Efficient Array Loops by Jeremy Howard
- Re: RFC 207 (v1) Array: Efficient Array Loops by David L. Nicol
- Re: RFC 207 (v1) Array: Efficient Array Loops by c.soeller
- Re: RFC 207 (v1) Array: Efficient Array Loops by Buddha Buck
**Re: RFC 207 (v1) Array: Efficient Array Loops**by Jeremy Howard- Re: RFC 207 (v1) Array: Efficient Array Loops by Jeremy Howard
- Re: RFC 207 (v1) Array: Efficient Array Loops by Buddha Buck
- 122 (v1): types and structures by Casey R. Tweten
- Re: 122 (v1): types and structures by Tom Christiansen
- Re: 122 (v1): types and structures by David L. Nicol
- Re: 122 (v1): types and structures by Tom Christiansen
- Re: 122 (v1): types and structures by David L. Nicol
- Re: 122 (v1): types and structures by David L. Nicol
- Re: 122 (v1): types and structures by Nathan Wiger
- Re: 122 (v1): types and structures by Michael Fowler

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