Re: Anonymous multidimensional array
Larry Wall larry-at-wall.org |Perl 6| wrote: On Tue, Jun 02, 2009 at 08:21:29AM -0700, yary wrote: : I do see a problem if there's more than one unspecified dimension. : Though I suppose an array of shape(*;*) as an lvalue might be a : constraint allowing assignment only of another 2D array? I don't see why we shouldn't use the capture shape of the value by default all the time, and do linear reshaping only if the value comes in as a flat list. We've gone to some pains to allow ephemeral shaping of values through captures, and it seems like it's good error checking to check the shape of the value against the shape of the container unless explicitly defeated. That is to say, if you erase the capture shape by putting the value into list context, it linearizes it, and then the container knows to reshape. Otherwise the container attempts to use the value slicily. Larry Consider: (@a,@b...@c) = SomeCapture; The first container, @a, being fixed-size will grab some of the elements. Now, what's left in SomeCapture is not even starting at a top-level boundary in the original structure. It's in the middle of some list some number of levels down. How does what's left of the capture imply the proper shape? It also means that given a multi-dim array, or a [**] array that can hold any morphology, the right-hand-size can't be a normal return from a map or whatever because you'll get the structure from _that_. The shape of the list is generally determined by the definitions of function return and looping statement semantics, and can't be used to formulate the structure you wanted. As it stands, list assignment is "list context" for the RHS. That is wise. If the Capture Revolution comes to that, it needs to be carefully thought out. --John
Re: Anonymous multidimensional array
I haven't gotten deep into the shape/array specs and I need to... nonetheless On Tue, Jun 2, 2009 at 9:55 AM, Larry Wall wrote: > I don't see why we shouldn't use the capture shape of the value > by default all the time, and do linear reshaping only if the value > comes in as a flat list. This highlights an edge case- in my mind at least, a "flat list" has a different shape from a one-row array. shape(*) or shape() vs shape(*;0)? Given the above, linear reshaping should not happen when given an explicitly-1D-shaped array on the right hand side, and that's something that should be spelled out and included in the spec tests. Or spell out the contradiction if I guessed wrong! >We've gone to some pains to allow ephemeral > shaping of values through captures, and it seems like it's good error > checking to check the shape of the value against the shape of the > container unless explicitly defeated. > > That is to say, if you erase the capture shape by putting the value > into list context, it linearizes it, and then the container knows > to reshape. Otherwise the container attempts to use the value slicily. I like this, though my comprehension is currently rather primitive.
Re: Anonymous multidimensional array
On Tue, Jun 02, 2009 at 08:21:29AM -0700, yary wrote: : I do see a problem if there's more than one unspecified dimension. : Though I suppose an array of shape(*;*) as an lvalue might be a : constraint allowing assignment only of another 2D array? I don't see why we shouldn't use the capture shape of the value by default all the time, and do linear reshaping only if the value comes in as a flat list. We've gone to some pains to allow ephemeral shaping of values through captures, and it seems like it's good error checking to check the shape of the value against the shape of the container unless explicitly defeated. That is to say, if you erase the capture shape by putting the value into list context, it linearizes it, and then the container knows to reshape. Otherwise the container attempts to use the value slicily. Larry
Re: Anonymous multidimensional array
On Mon, Jun 1, 2009 at 10:43 PM, John M. Dlugosz > And it should be an error if dimensions other than the highest are > unspecified. How can it know how to shape it? Use an explicit command to > shape up the argument in that case. I don't see why shape(2;*) is not a problem and shape(*;2) is a problem for an lvalue array, either each one (lazily?) demands an even number of elements, or they both fail. In general, multiply the size of the known dimensions, and that's the number of elements you need to fill up one more in the unspecified dimension direction. I do see a problem if there's more than one unspecified dimension. Though I suppose an array of shape(*;*) as an lvalue might be a constraint allowing assignment only of another 2D array?
Re: Anonymous multidimensional array
Larry Wall larry-at-wall.org |Perl 6| wrote: On Mon, Jun 01, 2009 at 08:23:41PM -0700, yary wrote: : How does one create an anonymous multidimensional array in p6? Not an : array of arrays or a capture of captures... But I would expect a shaped array to be able to coerce either of those into its internal format. And coercing captures into structure is basically what @@/slice context is for. Larry Right, after meditating on that very thing a few days ago, I conclude @A = @list; should work when one of the "containers" on the left happens to be shaped. The right is flattened, losing any structure it may have had, including the properly shaped thing already, a single linear list, or a different shape with a suitable number of elements. I would suggest that the assignment demand sufficient elements to fill, or be an integral number of lower-level units if the highest dimension is unspecified. You can always make up the difference by sticking 0 x * at the end of the right-hand-side if that was your intent. And it should be an error if dimensions other than the highest are unspecified. How can it know how to shape it? Use an explicit command to shape up the argument in that case. Also, if you were using an array of arrays, this will clobber that and fill the top array with items. If the top array is declared to be of Arrays, then the assignment will fail just like any other type constraint. But if the second-level arrays are fixed size, you can always write |@A on the left to re-fill those from the right hand side. --John
Re: Anonymous multidimensional array
On Mon, Jun 01, 2009 at 08:23:41PM -0700, yary wrote: : How does one create an anonymous multidimensional array in p6? Not an : array of arrays or a capture of captures... But I would expect a shaped array to be able to coerce either of those into its internal format. And coercing captures into structure is basically what @@/slice context is for. Larry
Anonymous multidimensional array
How does one create an anonymous multidimensional array in p6? Not an array of arrays or a capture of captures... I'm guessing it involves Array.new(:shape) or something like :shape(2;2), and that it's not yet implemented in Rakudo. Is anonymous multidimensional array creation covered in the synopses? Might be good to answer this explicitly in S09, 'less it's in there and I missed it. -y
