Em Ter, 2010-04-06 às 22:19 -0700, Damian Conway escreveu:
I kinda hope we can get a bit further away from the machine code
level of reality one of these decades. Perl 6 should not be
optimized for C semantics.
Agreed. But it should at least support those who need to work at
the machine
Larry mused:
Alternatively, maybe there should be some way to express infinite sets.
Not sure I like the idea of an infinite junction, but something resembling:
subset PowersOf2 of Int where any(1,2,4...*)
enum Perms of PowersOf2 Read Write Exec;
say Exec; # 4
Presumably the
Daniel Ruoso pointed out:
Using bitsets in Perl 6 is just as easy as using in Perl 5 -- which
happens to be the same as using in C, but it's not C...
constant PERM_WRITE = 0b0001;
constant PERM_READ = 0b0010;
constant PERM_EXEC = 0b0100;
constant PERM_NAMES = { PERM_WRITE = 'Write',
Damian Conway wrote:
I do like the idea of being able to specify the sequence of values of an
enumeration by using a series of some kind.
And I must say the one that feels most natural is the one that plays on
the equivalence of underlying equivalence of enums and constants, namely:
enum
On Wed, Apr 07, 2010 at 06:33:46AM -0700, Jon Lang wrote:
: That said, don't we already have a means of assigning specific values
: to individual members of an enum? I forget the exact syntax, but I
: believe that it involves an assignment operator within the
: enumeration. Mind you, this is
Jonathan Lang wrote:
Wouldn't that be C = 0...* ?
Indeed. Thanks for the correction.
That said, don't we already have a means of assigning specific values
to individual members of an enum? I forget the exact syntax,
The exact syntax is:
enum Perms [Read = 1, Write = 2, Exec = 4, Fold
We could make enum declarators even more like constant declarators
by using a pseudo assignment. Then we could use = instead of parens:
enum Perms = Read Write Exec Fold Spindle Mutilate Z= 1,2,4...*;
Hmm. That doesn't seem very like constant declarators. In a
constant declarator,
the
2010/4/6 Larry Wall la...@wall.org:
Set(Read | Write) # bogus, R|W is really 3 sets, R, W, and RW!
Set(Read Write) # okay, can only represent RW
Set(A | B) doesn't seem so bogus to me, if what you want is the power
set- not the original posters intent, but reasonable in other
-BEGIN PGP SIGNED MESSAGE-
Hash: SHA1
On Apr 7, 2010, at 00:52 , Larry Wall wrote:
more syntactic and/or semantic sugar. It's just a bit awkward, after
you say:
enum Permissions Read Write Exec;
subset Perms of Set of Permissions;
that the name of the single-member sets are
On Wed, 7 Apr 2010, yary wrote:
2010/4/6 Larry Wall la...@wall.org:
Set(Read | Write) # bogus, R|W is really 3 sets, R, W, and RW!
Set(Read Write) # okay, can only represent RW
Set(A | B) doesn't seem so bogus to me, if what you want is the power
set
Hmm, surely a power-set
One more idea: could you implement the sort of thing being asked for
by means of a buffer? That is, what's the difference between the
bitset being asked for and a Buf[boolean]? And could those
differences be addressed by composing a Buf[boolean] into a more
appropriate role?
Note also that Perl
An issue came up in a class I was teaching today...
There doesn't seem to be an easy way to create a type that allows a set
of enumerated bit-flags *and* all the combinations of those flags...and
nothing else.
For example:
enum Permissions ( Read = 0b0001, Write = 0b0010, Exec = 0b0100 );
First: what Damian said.
Second: Whatever syntax people come up with has to make it easy and
type-safe to name particular combinations of those bits.
In other words, you should be able to make a bitset with Unix-style
permissions:
OTHER_EXECUTE
OTHER_WRITE
OTHER_READ
On Tue, Apr 06, 2010 at 08:31:24PM -0700, Damian Conway wrote:
: An issue came up in a class I was teaching today...
:
: There doesn't seem to be an easy way to create a type that allows a set
: of enumerated bit-flags *and* all the combinations of those flags...and
: nothing else.
:
: For
Larry concluded:
I do freely admit that most Perlfolk are not used to thinking of
permissions in terms of set theory. But as I said, we're looking at
kind of a strange use case here, and perhaps not typical of the kinds
of sets of small numbers that people will be using in the future.
The
On Tue, Apr 06, 2010 at 10:19:15PM -0700, Damian Conway wrote:
: Larry concluded:
:
: I do freely admit that most Perlfolk are not used to thinking of
: permissions in terms of set theory. But as I said, we're looking at
: kind of a strange use case here, and perhaps not typical of the kinds
16 matches
Mail list logo
