hello!
first of all, i'm new to ruby and this list.
my question is, i have a class "Queue" which implements a queue as
linked list of "Item" objects. i'd like to implement an each method,
so i can do something like
queue.each do |item|
item.do_somethng
end
any help would be appreciated!
thanks,
philipp
It is a bit hard to help you, if we don't know your classes. But lets
say you have a class
class QueueNode
attr_accessor :next
...
end
and a class Queue with a variable @root holding the first entry of the
queue you could implement each as
class Queue
...
def each(&block)
node = @root
begin
block[node]
end while node = node.next
end
end
or you could use yield
class Queue
...
def each
node = @root
begin
yield node
end while node = node.next
end
end
that depends on personal preference.
hope to help,
Brian
On 01/09/05, Philipp Huber <huber.philipp@gmail.com> wrote:
hello!
first of all, i'm new to ruby and this list.
my question is, i have a class "Queue" which implements a queue as
linked list of "Item" objects. i'd like to implement an each method,
so i can do something likequeue.each do |item|
item.do_somethng
endany help would be appreciated!
thanks,
philipp
--
http://ruby.brian-schroeder.de/
Stringed instrument chords: http://chordlist.brian-schroeder.de/
Just one more hint in case you didn't know it. You should do
class Queue
include Enumerable
...
end
to get all the nice Enumerable methods for free.
all?, any?, collect, detect, each_with_index, entries, find,
find_all, grep, include?, inject, map, max, member?, min,
partition, reject, select, sort, sort_by, to_a, to_set, zip
regards,
Brian
On 01/09/05, Philipp Huber <huber.philipp@gmail.com> wrote:
hello!
first of all, i'm new to ruby and this list.
my question is, i have a class "Queue" which implements a queue as
linked list of "Item" objects. i'd like to implement an each method,
so i can do something likequeue.each do |item|
item.do_somethng
endany help would be appreciated!
thanks,
philipp
--
http://ruby.brian-schroeder.de/
Stringed instrument chords: http://chordlist.brian-schroeder.de/
thanks a lot, works exactly as i wanted 
On 9/1/05, Brian Schröder <ruby.brian@gmail.com> wrote:
On 01/09/05, Philipp Huber <huber.philipp@gmail.com> wrote:
> hello!
>
> first of all, i'm new to ruby and this list.
>
> my question is, i have a class "Queue" which implements a queue as
> linked list of "Item" objects. i'd like to implement an each method,
> so i can do something like
>
> queue.each do |item|
> item.do_somethng
> end
>
> any help would be appreciated!
> thanks,
> philipp
>
>It is a bit hard to help you, if we don't know your classes. But lets
say you have a class
class QueueNode
attr_accessor :next
...
endand a class Queue with a variable @root holding the first entry of the
queue you could implement each asclass Queue
...def each(&block)
node = @root
begin
block[node]
end while node = node.next
end
endor you could use yield
class Queue
...def each
node = @root
begin
yield node
end while node = node.next
end
endthat depends on personal preference.
hope to help,
Brian
--
http://ruby.brian-schroeder.de/Stringed instrument chords: http://chordlist.brian-schroeder.de/
Philipp Huber wrote:
thanks a lot, works exactly as i wanted
Two remarks:
- did you test this with an empty queue (I guess in that case @root will
be empty so you'll likely need something like
n = @root
while n
yield n.element
n = n.next
end
- by convention #each returns self which wasn't show in Brian's example.
Kind regards
robert
actually i did test it with a queue filled with a few elements. as you
said the condition for the while loop should be testet at the
beginning, otherwise nil could be returned.
so my code looks like this:
def each
node=@head
while node=node.next
yield node.content
end
end
do you have an example for the second remark, as i don't quite
understand what you mean
thanks,
philipp
Sorry for posting something that untested. But as I look again you
continue to have bugs in your code.
You are missing the first element. The following should work and also
return self. That allows you to do something like the following:
queue.each do | element | element.seen += 1 end.each do | element |
puts element end
Beware that the above example does not make that much sense, but I do
not have a better example ready.
def each
node=@head
while node
yield node.content
node=node.next
end
self
end
hope to help
Brian
On 01/09/05, Philipp Huber <huber.philipp@gmail.com> wrote:
actually i did test it with a queue filled with a few elements. as you
said the condition for the while loop should be testet at the
beginning, otherwise nil could be returned.
so my code looks like this:def each
node=@head
while node=node.next
yield node.content
end
enddo you have an example for the second remark, as i don't quite
understand what you meanthanks,
philipp
--
http://ruby.brian-schroeder.de/
Stringed instrument chords: http://chordlist.brian-schroeder.de/
of course your right, my variant leaves out the first element.
what's actually the sense behind returning self?
On 9/1/05, Brian Schröder <ruby.brian@gmail.com> wrote:
On 01/09/05, Philipp Huber <huber.philipp@gmail.com> wrote:
> actually i did test it with a queue filled with a few elements. as you
> said the condition for the while loop should be testet at the
> beginning, otherwise nil could be returned.
> so my code looks like this:
>
> def each
> node=@head
> while node=node.next
> yield node.content
> end
> end
>
> do you have an example for the second remark, as i don't quite
> understand what you mean
>
> thanks,
> philipp
>
>Sorry for posting something that untested. But as I look again you
continue to have bugs in your code.You are missing the first element. The following should work and also
return self. That allows you to do something like the following:queue.each do | element | element.seen += 1 end.each do | element |
puts element endBeware that the above example does not make that much sense, but I do
not have a better example ready.def each
node=@head
while node
yield node.content
node=node.next
end
self
endhope to help
Brian
--
http://ruby.brian-schroeder.de/Stringed instrument chords: http://chordlist.brian-schroeder.de/
Brian Schröder wrote:
actually i did test it with a queue filled with a few elements. as
you said the condition for the while loop should be testet at the
beginning, otherwise nil could be returned.
so my code looks like this:def each
node=@head
while node=node.next
yield node.content
end
enddo you have an example for the second remark, as i don't quite
understand what you mean
Just put "return self" or just "self" in the last line of your method
#each.
Sorry for posting something that untested. But as I look again you
continue to have bugs in your code.You are missing the first element. The following should work and also
return self. That allows you to do something like the following:
That's only true if head is nil for an empty queue. There are
implementations out there (for example java.util.LinkedList) where the
first element is never null. It might be though that it makes sense only
for a doubly linked list.
queue.each do | element | element.seen += 1 end.each do | element |
puts element endBeware that the above example does not make that much sense, but I do
not have a better example ready.def each
node=@head
while node
yield node.content
node=node.next
end
self
end
That's what I suggested, isn't it?
Kind regards
robert
On 01/09/05, Philipp Huber <huber.philipp@gmail.com> wrote:
Philipp Huber wrote:
of course your right, my variant leaves out the first element.
what's actually the sense behind returning self?
Don't ask. There's a dark secret connected to this. Noone ever lived to
tell. Many have tried to provide explanations (such as support of method
chaining) but the truth was never revealed...
Cheers
robert
Brian Schröder wrote:
>> actually i did test it with a queue filled with a few elements. as
>> you said the condition for the while loop should be testet at the
>> beginning, otherwise nil could be returned.
>> so my code looks like this:
>>
>> def each
>> node=@head
>> while node=node.next
>> yield node.content
>> end
>> end
>>
>> do you have an example for the second remark, as i don't quite
>> understand what you meanJust put "return self" or just "self" in the last line of your method
#each.> Sorry for posting something that untested. But as I look again you
> continue to have bugs in your code.
>
> You are missing the first element. The following should work and also
> return self. That allows you to do something like the following:That's only true if head is nil for an empty queue. There are
implementations out there (for example java.util.LinkedList) where the
first element is never null. It might be though that it makes sense only
for a doubly linked list.> queue.each do | element | element.seen += 1 end.each do | element |
> puts element end
>
> Beware that the above example does not make that much sense, but I do
> not have a better example ready.
>
> def each
> node=@head
> while node
> yield node.content
> node=node.next
> end
> self
> endThat's what I suggested, isn't it?
It is - I'm sorry, I'm task-switching in my mind too fast at the
moment. I will concentrate on my thesis now ...
best regards,
Brian
On 01/09/05, Robert Klemme <bob.news@gmx.net> wrote:
> On 01/09/05, Philipp Huber <huber.philipp@gmail.com> wrote:
Kind regards
robert
--
http://ruby.brian-schroeder.de/
Stringed instrument chords: http://chordlist.brian-schroeder.de/
Robert Klemme wrote:
Philipp Huber wrote:
of course your right, my variant leaves out the first element.
what's actually the sense behind returning self?Don't ask. There's a dark secret connected to this. Noone ever lived to
tell. Many have tried to provide explanations (such as support of method
chaining) but the truth was never revealed...
Chaining is the reason.
a.please.do.this
instead of:
a.please
a.do
a.this
Cheers
robert
--
Daryl Richter
Platform Author & Director of Technology
(( Brandywine Asset Management )
( "Expanding the Science of Global Investing" )
( http://www.brandywine.com ))