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comp.lang.ruby

replace values in hash

Jason

11/5/2008 6:54:00 AM

how would I iterate over a hash, such as

x = { 'a' => "hi", 'b' => nil, 'c' => "do"}

and replace nil values with 'foo' then return the hash again?
--
Posted via http://www.ruby-....
7 Answers

Trans

11/5/2008 7:40:00 AM

0

On Nov 5, 1:53=A0am, Jason Lillywhite <jason.lillywh...@gmail.com>
wrote:
> how would I iterate over a hash, such as
>
> x =3D { 'a' =3D> "hi", 'b' =3D> nil, 'c' =3D> "do"}

x.each{ |k,v| x[k] =3D 'foo' unless v }

However, it is not always sane to alter something while you are
iterating over it. So,

h =3D {}
x.each{ |k,v| h[k] =3D v.nil? ? v : 'foo' }
x.replace(h)

Or use Facets Enumerable#mash (alias #graph)

require 'facets/enumerable/mash'

x =3D x.mash{ |k,v| [k, v.nil? ? v : 'foo'] }

http://facets.rubyforge.org/doc/api/core/classes/Enumerable.ht...

7.

Jason

11/5/2008 7:55:00 AM

0

Thank you!

However, I am getting undefined method 'mash' even though I do require
'facets/enumerable/mash'

am I missing something?
--
Posted via http://www.ruby-....

Sarcar, Shourya C (GE Healthcare)

11/5/2008 10:52:00 AM

0

=20

> -----Original Message-----
> From: jason.lillywhite@gmail.com [mailto:jason.lillywhite@gmail.com]=20
> Sent: Wednesday, November 05, 2008 12:24 PM
> To: ruby-talk ML
> Subject: replace values in hash
>=20
> how would I iterate over a hash, such as
>=20
> x =3D { 'a' =3D> "hi", 'b' =3D> nil, 'c' =3D> "do"}


h.keys.each {|d| h[d] =3D "foo" if h[d] =3D=3D nil}

Trans

11/5/2008 3:31:00 PM

0



On Nov 5, 2:54=A0am, Jason Lillywhite <jason.lillywh...@gmail.com>
wrote:
> Thank you!
>
> However, I am getting undefined method 'mash' even though I do require
> 'facets/enumerable/mash'
>
> am I missing something?

Don't think so. It's working fine for me.

What version of Ruby and Facets and what platform are you running?

T.

Brian Adkins

11/5/2008 5:40:00 PM

0

Jason Lillywhite <jason.lillywhite@gmail.com> writes:

> how would I iterate over a hash, such as
>
> x = { 'a' => "hi", 'b' => nil, 'c' => "do"}
>
> and replace nil values with 'foo' then return the hash again?

~/temp$ cat -b temp.rb
1 require 'pp'

2 class Hash
3 def replace_value old, new
4 self.inject({}) do |result,pair|
5 k, v = pair[0], pair[1]
6 result[k] = (v == old) ? new : v
7 result
8 end
9 end
10 end

11 x = { 'a' => "hi", 'b' => nil, 'c' => "do", :d => nil }
12 pp x
13 y = x.replace_value(nil, 'foo')
14 pp y
~/temp$ ruby temp.rb
{"a"=>"hi", "b"=>nil, :d=>nil, "c"=>"do"}
{"a"=>"hi", "b"=>"foo", "c"=>"do", :d=>"foo"}

--
Brian Adkins
http://www....
http://lojic...

Trans

11/5/2008 6:10:00 PM

0



On Nov 5, 10:31=A0am, Trans <transf...@gmail.com> wrote:
> On Nov 5, 2:54=A0am, Jason Lillywhite <jason.lillywh...@gmail.com>
> wrote:
>
> > Thank you!
>
> > However, I am getting undefined method 'mash' even though I do require
> > 'facets/enumerable/mash'
>
> > am I missing something?
>
> Don't think so. It's working fine for me.
>
> What version of Ruby and Facets and what platform are you running?

For anyone who is interested, here's the definition (and some side
notes about how it evolved).

def mash(&yld)
if yld
inject({}) do |h, *kv| # Used to be inject({}) do |h,kv|
r =3D *yld[*kv] # The *-op works different from to_a on
single element hash!!!
nk, nv =3D *r # Used to be nk, nv =3D
*yld[*kv].to_a.flatten
h[nk] =3D nv
h
end
else
Enumerator.new(self,:mash) # Used to be Hash[*self.to_a]
end
end

T.

James Herdman

11/10/2008 2:35:00 PM

0

[Note: parts of this message were removed to make it a legal post.]

Not bad. Let's tighten it up a little:

class Hash
def replace_value(old, new)
self.inject({}) do |result, (key, existing_value)|
result[key] = (value == old) ? new : existing_value
result
end
end
end

This isn't bad, but you wouldn't want to do this for large Hashes since you
end up copying the original.

James

On Wed, Nov 5, 2008 at 12:38 PM, Brian Adkins <lojicdotcom@gmail.com> wrote:

> Jason Lillywhite <jason.lillywhite@gmail.com> writes:
>
> > how would I iterate over a hash, such as
> >
> > x = { 'a' => "hi", 'b' => nil, 'c' => "do"}
> >
> > and replace nil values with 'foo' then return the hash again?
>
> ~/temp$ cat -b temp.rb
> 1 require 'pp'
>
> 2 class Hash
> 3 def replace_value old, new
> 4 self.inject({}) do |result,pair|
> 5 k, v = pair[0], pair[1]
> 6 result[k] = (v == old) ? new : v
> 7 result
> 8 end
> 9 end
> 10 end
>
> 11 x = { 'a' => "hi", 'b' => nil, 'c' => "do", :d => nil }
> 12 pp x
> 13 y = x.replace_value(nil, 'foo')
> 14 pp y
> ~/temp$ ruby temp.rb
> {"a"=>"hi", "b"=>nil, :d=>nil, "c"=>"do"}
> {"a"=>"hi", "b"=>"foo", "c"=>"do", :d=>"foo"}
>
> --
> Brian Adkins
> http://www....
> http://lojic...
>
>