Re: [S29] pick on other things than junctions
Ingo Blechschmidt iblech at web.de writes:
then it has a better chance of working, presuming someone has the
gumption to write .pick on hashes, which doesn't look entirely trivial
to do right.
thinking out loudI'm sure I overlooked something, but the following
seems to be correct and is not *that* difficult :):
class Hash;
...;
method pick() is rw {
# First pick a random key.
my $key = .keys.pick;
# Then return an appropriate Proxy object:
return new Proxy:
FETCH = {
Ok. While typing the C{ here, I realized you were correct :)
It'd be reasonable simple if there was a .get_pair_by_key method
(which'd do appropriate binding and'd be Cis rw):
method pick() is rw {
my $key = .keys.pick;
my $pair := .get_pair_by_key($key);
return $pair;
}
well :)
# Ignoring multi-dimensionality
method pairbykey($key is copy) is rw {
return new Proxy:
FETCH = - $pair { $self{$key} },
STORE = - $pair {
my ($newkey, $newval) = $pair.kv;
$self.delete($key); # Delete old entry
$self{$key = $newkey} = $newval; # Add new entry
};
}
# Correct?
BTW, this would make the following work, too:
for %hash.pairs - $pair is rw { $pair = ... }
# Implementation of Hash::pairs:
method pairs (Any|Junction [EMAIL PROTECTED]) {
my @keys = @keytests ?? .keys.grep:{ $_ ~~ any @keytests } :: .keys;
return .pairbykey.(@keys);
}
# Correct?
The next logical step to full rw-ness would be a rw .pairs (@keytests
removed for simplicity):
method pairs ($self:) is rw {
return new Proxy:
FETCH = { .pairbykey.(.keys) },
STORE = - [EMAIL PROTECTED] {
.delete($_) for .keys;
# [Is there a .clear? The obvious way, %hash = ()/
# $self = {} won't work of course.]
$self{$_.key} = $_.value for @new;
};
}
# Correct?
/thinking out loud
--Ingo
--
Linux, the choice of a GNU | Mr. Cole's Axiom: The sum of the
generation on a dual AMD | intelligence on the planet is a constant;
Athlon!| the population is growing.
Re: [S29] pick on other things than junctions
Hi,
Trey Harris wrote:
In a message dated Mon, 4 Apr 2005, Ingo Blechschmidt writes:
What does pick return on hashes? Does it return a random value or a
random pair? (I suppose returning a pair is more useful.)
I'd assume in all cases that pick returns an *alias*, and in the case
of hashes, an alias to the pair:
# Add entropy to your hash
for 1..$entropy_thresshold {
%hash.pick.value *= rand $scribble_factor;
}
I like that, too. So:
my @array = a b c d;
my $elem = @array.pick;
$elem = z; # $elem now z, @array unchanged
my @array = a b c d;
my $elem := @array.pick;
$elem = z; # $elem now z, @array changed
# (any(@array) eq z now true)
Same for hashes:
my %hash = (a = 1, b = 2);
my $pair = %hash.pick;
$pair = ...; # %hash unchanged
my %hash = (a = 1, b = 2),
my $pair := %hash.pick;
$pair = ...; # %hash changed
--Ingo
--
Linux, the choice of a GNU | Black holes result when God divides the
generation on a dual AMD | universe by zero.
Athlon!|
Re: [S29] pick on other things than junctions
On Tue, Apr 05, 2005 at 02:38:05PM +0200, Ingo Blechschmidt wrote:
: Hi,
:
: Trey Harris wrote:
: In a message dated Mon, 4 Apr 2005, Ingo Blechschmidt writes:
: What does pick return on hashes? Does it return a random value or a
: random pair? (I suppose returning a pair is more useful.)
:
: I'd assume in all cases that pick returns an *alias*, and in the case
: of hashes, an alias to the pair:
:
:# Add entropy to your hash
:for 1..$entropy_thresshold {
:%hash.pick.value *= rand $scribble_factor;
:}
:
: I like that, too. So:
: my @array = a b c d;
: my $elem = @array.pick;
: $elem = z; # $elem now z, @array unchanged
:
: my @array = a b c d;
: my $elem := @array.pick;
: $elem = z; # $elem now z, @array changed
:# (any(@array) eq z now true)
But what should we call pick without replacment? .peck?
Unfortunately @array.=pick isn't what you want. It would reduce the
array to one element. On the other hand, if .pick takes an argument
saying how many to pick, then maybe
@array.=pick([EMAIL PROTECTED])
gives you a random shuffle. Unfortunately,
@array.=pick(@array - 1)
won't tell you which one it left out.
: Same for hashes:
: my %hash = (a = 1, b = 2);
: my $pair = %hash.pick;
: $pair = ...; # %hash unchanged
:
: my %hash = (a = 1, b = 2),
: my $pair := %hash.pick;
: $pair = ...; # %hash changed
I'm not sure that works. We don't quite have pairs as first class
containers. Binding would try to use a pair as a named argument, and
would fail unless the key happened to be 'pair', which it isn't in this
case. However, if you were to say,
my Pair $pair := %hash.pick;
then it has a better chance of working, presuming someone has the gumption
to write .pick on hashes, which doesn't look entirely trivial to do right.
Larry
Re: [S29] pick on other things than junctions
Hi,
Larry Wall wrote:
: Same for hashes:
[...]
: my %hash = (a = 1, b = 2),
: my $pair := %hash.pick;
: $pair = ...; # %hash changed
I'm not sure that works. We don't quite have pairs as first class
containers. Binding would try to use a pair as a named argument, and
would fail unless the key happened to be 'pair', which it isn't in
this case.
Oh yes, of course. Others may be interested in
http://groups.google.com/groups?threadm=x7wtsvo0fs.fsf%40mail.sysarch.com.
then it has a better chance of working, presuming someone has the
gumption to write .pick on hashes, which doesn't look entirely trivial
to do right.
thinking out loudI'm sure I overlooked something, but the following
seems to be correct and is not *that* difficult :):
class Hash;
...;
method pick() is rw {
# First pick a random key.
my $key = .keys.pick;
# Then return an appropriate Proxy object:
return new Proxy:
FETCH = {
Ok. While typing the C{ here, I realized you were correct :)
It'd be reasonable simple if there was a .get_pair_by_key method
(which'd do appropriate binding and'd be Cis rw):
method pick() is rw {
my $key = .keys.pick;
my $pair := .get_pair_by_key($key);
return $pair;
}
--Ingo
--
Linux, the choice of a GNU | Mathematicians practice absolute freedom.
generation on a dual AMD | -- Henry Adams
Athlon!|
[S29] pick on other things than junctions
Hi, I remembered Damian saying that pick does not only work on junctions, but on arrays and hashes, too (and I even found his posting :): http://groups.google.com/groups?selm=420DB295.3000902%40conway.org). Are the following assumptions correct? my $junc = 1|2|3; print $junc.pick; # 1, 2, or 3 print pick $junc; # same my @array = a b c; print @array.pick; # a, b, or c print pick @array; # same What does pick return on hashes? Does it return a random value or a random pair? (I suppose returning a pair is more useful.) --Ingo -- Linux, the choice of a GNU | The next statement is not true. The generation on a dual AMD | prevoius statement is true. Athlon!|
Re: [S29] pick on other things than junctions
Ingo Blechschmidt wrote: I remembered Damian saying that pick does not only work on junctions, but on arrays and hashes, too (and I even found his posting :): http://groups.google.com/groups?selm=420DB295.3000902%40conway.org). Are the following assumptions correct? my $junc = 1|2|3; print $junc.pick; # 1, 2, or 3 print pick $junc; # same my @array = a b c; print @array.pick; # a, b, or c print pick @array; # same What does pick return on hashes? Does it return a random value or a random pair? (I suppose returning a pair is more useful.) Most likely a pair. Now if I could only find some more time to work on S29. I've been making progress (slowly) on getting the string functions written up, but life seems to be conspiring against rapid progress. -- Rod Adams
Re: [S29] pick on other things than junctions
In a message dated Mon, 4 Apr 2005, Ingo Blechschmidt writes:
What does pick return on hashes? Does it return a random value or a
random pair? (I suppose returning a pair is more useful.)
I'd assume in all cases that pick returns an *alias*, and in the case of
hashes, an alias to the pair:
# Add entropy to your hash
for 1..$entropy_thresshold {
%hash.pick.value *= rand $scribble_factor;
}
Trey
Re: [S29] pick on other things than junctions
I'd assume you'd get an *alias* to a random pair:
# Test error-correction
for 1..$entropy_threshhold {
%hash.pick.value = rand $scribble_factor;
}
Trey
In a message dated Mon, 4 Apr 2005, Ingo Blechschmidt writes:
Hi,
I remembered Damian saying that pick does not only work on junctions,
but on arrays and hashes, too (and I even found his posting :):
http://groups.google.com/groups?selm=420DB295.3000902%40conway.org).
Are the following assumptions correct?
my $junc = 1|2|3;
print $junc.pick; # 1, 2, or 3
print pick $junc; # same
my @array = a b c;
print @array.pick; # a, b, or c
print pick @array; # same
What does pick return on hashes? Does it return a random value or a
random pair? (I suppose returning a pair is more useful.)
--Ingo
--
Re: [S29] pick on other things than junctions
In a message dated Mon, 4 Apr 2005, Ingo Blechschmidt writes:
What does pick return on hashes? Does it return a random value or a
random pair? (I suppose returning a pair is more useful.)
I'd assume in all cases that pick returns an *alias*, and in the case of
hashes, an alias to the pair:
# Add entropy to your hash
for 1..$entropy_thresshold {
%hash.pick.value *= rand $scribble_factor;
}
Trey
Re: [S29] pick on other things than junctions
Yikes. Sorry about the ressends... my email client kept dying and I
thought the mail was lost. Guess not. :-)
Trey
In a message dated Mon, 4 Apr 2005, Trey Harris writes:
In a message dated Mon, 4 Apr 2005, Ingo Blechschmidt writes:
What does pick return on hashes? Does it return a random value or a
random pair? (I suppose returning a pair is more useful.)
I'd assume in all cases that pick returns an *alias*, and in the case of
hashes, an alias to the pair:
# Add entropy to your hash
for 1..$entropy_thresshold {
%hash.pick.value *= rand $scribble_factor;
}
Trey
--
