hi,
is there anywhere a class that does soemthing
akin to java.util.SortedMap? that is sorting
and iterating over the hash in the order of its
keys.
i had a look into facets dictionary but that does
only preserve the ordering of insertion which
is not what i want.
any other suggestions?
ciao robertj
Hi Robert,
i had a look into facets dictionary but that does
only preserve the ordering of insertion which
is not what i want.
The dictionary class in Facets/Calibre is basically the ordered hash
written by jan molic. I’ve been wanting to improve on it. This looks
like the oppornunity. What is it that you need? I’d be happy to work in
your critera.
Thanks,
T.
On Thursday 08 December 2005 12:37 pm, robertj wrote:
hi,
is there anywhere a class that does soemthing
akin to java.util.SortedMap? that is sorting
and iterating over the hash in the order of its
keys.
When I tried it, it seemed that Ruby automatically sorted the keys. I’m
not
sure if this is what you want, but see this:
HTH
SteveT
Steve L.
[email protected]
From: “robertj” [email protected]
is there anywhere a class that does soemthing
akin to java.util.SortedMap? that is sorting
and iterating over the hash in the order of its
keys.
Perhaps rbtree?
http://raa.ruby-lang.org/project/ruby-rbtree/
Regards,
Bill
Steve L. wrote:
Ruby Basic Tutorial
Not sure what “it” is, but Hash#sort will convert the hash to a list of
lists, sorted by their keys
Then others have put in rbtrees, arrays accessed by keywords,
http://raa.ruby-lang.org/project/ruby-rbtree/
http://codeforpeople.com/lib/ruby/arrayfields/arrayfields-3.5.0/README
Gene T. wrote:
When I tried it, it seemed that Ruby automatically sorted the keys. I’m not
sure if this is what you want, but see this:
Ruby Basic Tutorial
Not sure what “it” is, but Hash#sort will convert the hash to a list of
lists, sorted by their keys
True, but unless you need the values stored in order internally, just do
this:
hash.sort.each{ |e| puts “#{e[0]} => #{e[1]}” }
Regards,
Dan
hi,
the only real requirement is
that #each returns me the
key value pairs in an ordered fashion.
default ordering should be by key.
one could but think of also having
a switch that allows for ordering by
value.
ciao robertj
hi daniel,
hash.sort.each{ |e| puts “#{e[0]} => #{e[1]}” }
this has the effect that clients of that hash
need to know that they must order the hash +
the interface for iteration has changed.
instead of hash.each { |k, v| …} you get hash.sort.each { |v| …}
in short your solution requires “sorting” to become part of
the “official” interface of my hash.
ciao robertj
On Dec 8, 2005, at 12:57 PM, robertj wrote:
the “official” interface of my hash.
You could easily wrap a Hash and provide an each() that sorted before
yielding.
James Edward G. II
hi T.
another idea would be to be able to define
a comperator block that does the actual
comparisson.
ciao robertj
robertj wrote:
another idea would be to be able to define
a comperator block that does the actual
comparisson.
I see. So you want a way to tell the object itself how it’s to order
the elements. The default wprobably should stay insertion order, but
you’d like to specify an alternative like alpahnumeric key order. Is
that right? If so, I can put in an optional parameter for that no
problem. Although you may have to set it post instantiation, something
like
d = Dictionary.new.sort_on { |a,b| a.key <=> b.key }
As a shorthand:
d = Dictionary.new.sort_on(:key)
While I would like to add this as a block/parameter of the initialize
method itself, it may be a problem b/c this should probably be used for
a default block like hash has.
T.
robertj wrote:
value.
ciao robertj
hi,
if speed isn’t an issue:
class SortedHash < Hash
alias :unsorted_each :each
def each
keys.sort.each{|k| yield k, self[k]}
end
end
h = SortedHash[*Array.new(20){rand(100)}]
h.each{|k, v| puts “#{k} => #{v}”}
this isn’t meant to replace a red black tree
implementation of course.
cheers
Simon
Thank robertj I’ll work on it now.
By the way have you seen calibre/association? That’s kind of neat. It
isn’t quite like a regular hash, but you can use it do order hash-like
strucutures.
require ‘calibre/association’
assoc_array = [ :a >> 1, :b >> :2, :c >> 3 ]
assoc_array.each{ |k,v| p k,v }
produces
:a
1
:b
2
:c
3
T.
On Fri, 9 Dec 2005, robertj wrote:
ciao robertj
harp:~ > cat a.rb
require “alib”
include ALib
oh = OrderedHash::new
oh[“first”] = 42
oh[“second”] = “forty-two”
puts “—”
oh.each{|k,v| puts “#{ k } : #{ v }”}
harp:~ > ruby a.rb
first : 42
second : forty-two
-a
James Edward G. II wrote:
You could easily wrap a Hash and provide an each() that sorted before
yielding.
I’ve been discussing this off and on for years. What you say is true,
and it’s also true that we can easily write a class that acts like an
ordered hash.
The problem is literals or constants. Nothing I do will ensure that
the hash { x=>a, y=>b, z=>c } will be iterated over in that
original specified order.
Hal
On Fri, 9 Dec 2005, Trans wrote:
puts “—”
oh.each{|k,v| puts “#{ k } : #{ v }”}
harp:~ > ruby a.rb
first : 42
second : forty-two
Insertion order?
yup. this is my favourite usage:
harp:~ > cat a.rb
require "alib"
config = ALib::OrderedAutoHash::new
config["db"]["port"] = 5432
config["db"]["host"] = "localhost"
config["db"]["host"] = "postgres"
config["site"]["uri"] = "http://codeforpeople.com"
y config
harp:~ > ruby a.rb
---
db:
port: 5432
host: postgres
site:
uri: http://codeforpeople.com
ahhh.
-a
Okay, I have preliminary implementation of Dictionary class with
built-in ordering. Its important to note that the implementation isn’t
as efficient as sorting externally b/c the class sorts the pairs every
time #each is called (if order_by is set). There are ways to improve
the efficiency, but that’s a task for another day.
The basic way to do it:
d = Dictionary.new.order_by{ |k,v| k }
This creates a dictionary orderd by the key. The block allows you to
define almost any order mechisim you like. Since alphanumeric key order
is likely the most common (after the default of insertion order) I
created a special constructor method just for it:
d = Dictionary.alpha
This does the exact same thing is the last example. The only thing I’m
not so sure about is the name of this method. Is this good or would
something else be better?
BTW, Ara, you inspired me:
d = Dictionary.auto
will do the same as OrderedAutoHash::new. Thanks for that idea. Of
course, I have the same question about my choice of method name here
too.
T.