On 11 Mar 2013, at 10:39, Mark Morgan Lloyd wrote:
Jonas Maebe wrote:
On 10 Mar 2013, at 15:00, Juha Manninen wrote:
There are no 8-bit CPUs
supported by FPC that would justify it.
It is unrelated to 8 bit cpus. Even Turbo Pascal 1.0 ran on a 16
bit cpu.
Provided that one calls a Z80 16-bit :-) More to the point: do any
current CPUs have e.g. vector operations that suggest a realistic
maximum size?
The current x86's bit test/set instructions support addressing the
complete 32/64 bit address space. But the original 8086 didn't have
any vector instructions at all. Again: this limitation is unrelated to
instruction sets, it's about deciding on a point at which you're going
to waste a lot of memory by using a plain bitmap.
There is a already a test for larger set support:
http://svn.freepascal.org/svn/fpc/trunk/tests/test/tset6.pp
Nobody has worked yet on implementing it, but if anyone thinks it's
easy to do, please go ahead. For larger sets, especially if they
are sparse, a simple hashtable-based class would probably be much
faster and memory efficient than simply extending the default
implementation though. With operator overloading and generics you
might even be able to use more or less the same syntax as with
built-in sets.
For larger sets... OK, how /does/ one declare a set of UTF-8
characters?
An UTF-8 character is not an ordinal data type and hence support for
"set of <utf-8 character>" is orthogonal to support for larger sets.
If you store them in strings or arrays, then you need a hashtable of
strings or arrays (and/or support for sets of strings or arrays, which
would probably be implemented using... a hashtable).
Jonas
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