On Saturday, 28 July 2012 at 14:36:26 UTC, Ali Çehreli wrote:
On 07/28/2012 06:49 AM, Philip Daniels wrote:
> It seems to
> be something to do with whether the array is static or
dynamic.
Good catch! :) Welcome to D where static arrays (aka
"fixed-length arrays") and dynamic arrays (aka "slices") are
different beasts.
A number of factors are at play here:
1) Static arrays are value types. As a result, the entire array
gets copied when pass to a function (e.g. reduce) as an
argument.
2) The length of static arrays cannot change.
3) Phobos is a range-based library. reduce() is an algorithm
that not more than an InputRange.[*] InputRanges are naturally
consumed as they are being iterated over.
For the reasons above, a static array is not usable by
reduce(). Your solution of taking a slice of all of the
elements first by _word_tables[] is the correct solution (and
very cheap, thanks to D's slices).
Ali
[*] Arguably, reduce() could have a specialization that worked
on RandomAccessRanges (static arrays included), making life
easier. I don't see why that could not be added to Phobos.
Thanks for the explanation Ali. I was planning on converting the
array to dynamic anyway, since the ultimate size is dependent
upon the program's input, so I think I'll do that now.
