Hash#slice

Ruby
1

is this consistent with other peoples stdlib hacks?

class Hash
def slice *keys, &block
if block
each do |key, val|
boolean = block.call(key, val)
keys << key if boolean
end
end
hash = self
keys.inject({}){|returned, key| returned.update key => hash[key]}
end
end

??

a @ http://codeforpeople.com/

2

On Apr 12, 5:00 pm, ara howard [email protected] wrote:

 hash = self
 keys.inject({}){|returned, key| returned.update key => hash[key]}

end
end

??

Let see… Facets:

class Hash

# Returns a new hash with only the given keys.

def slice(*keep_keys)
  h = {}
  keep_keys.each do |key|
    h[key] = fetch(key)
  end
  h
end

# Replaces hash with a new hash having only the given keys.
# This return the hash of keys removed.

def slice!(*keep_keys)
  removed = except(*keep_keys)
  replace(slice(*keep_keys))
  removed
end

end

T.

3

On Apr 12, 3:00 pm, ara howard [email protected] wrote:

 hash = self
 keys.inject({}){|returned, key| returned.update key => hash[key]}

end
end

http://raa.ruby-lang.org/project/hashslice/

Regards,

Dan

4

On Apr 12, 2008, at 5:12 PM, Trans wrote:

 end

end

end

okay, you should add the block form :wink:

headers.slice{|k,| k =~ %r/^HTTP_/}

handy…

cheers.

a @ http://codeforpeople.com/

5

On Sun, Apr 13, 2008 at 2:51 AM, ara.t.howard [email protected]
wrote:

h = {}
removed = except(*keep_keys)

h.h. the 14th dalai lama

Hmm maybe it is a more consistent approach not to add a block to slice.

FWIAC, I use hselect, kselect and vselect, the simplified code
goes like this (1) of course
def kselect &blk
hselect{ |k,| blk.call(k) }
end
def vselect &blk
hselect{ |_,v| blk.call(v) }
end
def hselect &blk
#almost Tom’s code of course
end

You might write
h.slice(*[*1…10]){|k,v| whatever k, v }
which indeed I like

I would write
h.slice(*[*1…10]).hselect{|k,v| whatever k, v}
which indeed I like less, but I dislike the inconsistency of #select
now.

The ideal solution might be to add a block to Enumerator#select too,
what about that?

Cheers
Robert

(1) simplified because the magic dot notation implementing proxy is of
no interest here.

–
http://ruby-smalltalk.blogspot.com/

Whereof one cannot speak, thereof one must be silent.
Ludwig Wittgenstein

6

On Sun, Apr 13, 2008 at 12:04 PM, Trans [email protected] wrote:

end
end
–
end
hash.keys.select
hash.values.select
We were talking about getting sliced hashes not sliced key or value
arrays. Maybe in the future there will be a saying
“the best thing since the invention of sliced hashes by Ara T. Howard”
the real inventor gets always forgotten sorry for Facets I can not
change future history :wink:
The ideal solution might be to add a block to Enumerator#select too,
what about that?

Hmm… I don’t understand Enumerator#select comes from
Enumerable#select and already takes a block.
Stupid me again I meant Array#slice. I feel that my brain is
terribly disconnected from the keyboard, (I believe that Scotty was
right when talking into the mouse LOL). Well proofreading my posts
would be an option though :).

I will express myself in Ruby

assert_nothing_raised (“You see it would be nice that Array#slice and
Hash#slice had (almost) the same interface”) do
[*1…100].slice(1…10){ |x| x.zero? }
end

Sorry
R.

http://ruby-smalltalk.blogspot.com/

Whereof one cannot speak, thereof one must be silent.
Ludwig Wittgenstein

7

On Apr 13, 4:58 am, “Robert D.” [email protected] wrote:

def slice(*keep_keys)
def slice!(*keep_keys)

Hmm maybe it is a more consistent approach not to add a block to slice.
def hselect &blk
#almost Tom’s code of course
end

Why not?

hash.keys.select
hash.values.select

You might write
h.slice(*[*1…10]){|k,v| whatever k, v }
which indeed I like

I would write
h.slice(*[*1…10]).hselect{|k,v| whatever k, v}
which indeed I like less, but I dislike the inconsistency of #select now.

The ideal solution might be to add a block to Enumerator#select too,
what about that?

Hmm… I don’t understand Enumerator#select comes from
Enumerable#select and already takes a block.

T.

8

On Apr 13, 2008, at 6:22 AM, Robert D. wrote:

assert_nothing_raised (“You see it would be nice that Array#slice and
Hash#slice had (almost) the same interface”) do
[*1…100].slice(1…10){ |x| x.zero? }
end

now that does make sense :wink:

a @ http://codeforpeople.com/

9

On Apr 13, 2008, at 4:04 AM, Trans wrote:

Why not?

hash.keys.select
hash.values.select

because the goal is to return a hash, not an array… i think some
wires got crossed though :wink:

a @ http://codeforpeople.com/

10

On Apr 12, 2008, at 11:14 PM, Daniel B. wrote:

http://raa.ruby-lang.org/project/hashslice/

Ack, apologies to those who followed the link off that page to a 404.
Fixed now.