What is the ruby way to do this?

Ruby
41

On 11/23/05, David A. Black [email protected] wrote:

Hi –

On Wed, 23 Nov 2005, Lyndon S. wrote:

It would be nice if there was a wiki page somewhere of these
Uberdioms…

I’m not sure what you mean. A wiki page of… ?

Sorry :slight_smile:

Uberdioms = Uber Idioms = Made up word representing powerfull and
sometimes
lacking in immediate clarity language constructs that programmers should
be aware of but not necessarily utilising in all circumstances.

David

42

Nice RaDD work ( Rapid Documentation Development ) !

43

On Wed, Nov 23, 2005 at 01:58:01PM +0900, Joel VanderWerf wrote:

It’s not completely useless:

irb(main):001:0> noargs = proc { || 3 }
=> #Proc:0xb7b3558c@:1(irb)
irb(main):002:0> noargs[]
=> 3
irb(main):003:0> noargs[2]
ArgumentError: wrong number of arguments (1 for 0)
from (irb):3
from (irb):3

Maybe not for long

[lambda{ }.arity, RUBY_VERSION] # => [0, “1.9.0”]

vs.

[lambda{ }.arity, RUBY_VERSION] # => [-1, “1.8.3”]

44

Heh, and to think the only reason I did it was because I figured just
having
the { [] } would confuse things ( badly formed hash declaration ) so I
put
the goalposts in just to be sure that it saw things as a block body …

I’ll gladly take credit, I’m glad I’ll be remembered for something now (
heh, need to get that into the rubyscore app )… for my “empty
goalpost”
strategem :wink: . I’m not Dave T. or DHH or _why … or matz … or any
of
the countless others that have helped me better myself as a Rubyist, but
hopefully one day I’ll get to have a big impact … and pay them all
back. I
thank you all everyday I get to play with Ruby.

Anyways, You could seperate them if you didn’t want them to look like or
…
like …

{ | | [] } … although that’s kinda ugly to me.

I’d be just as happy to use the new block syntax ->{ [] } … when is
that
going to see the light of day ???

j.

–
“Remember. Understand. Believe. Yield! → http://ruby-lang.org”

Jeff W.

45

Hi –

On Wed, 23 Nov 2005, Joel VanderWerf wrote:

I believe that’s the first empty || I’ve ever seen. It’s awfully
irb(main):003:0> noargs[2]
ArgumentError: wrong number of arguments (1 for 0)
from (irb):3
from (irb):3

Interesting. I wonder why. And it’s yet another case where
proc/lambda and Proc.new are different:

noargs = Proc.new { || 3 }
=> #Proc:0x0033654c@:8(irb)
irb(main):009:0> noargs[2]
=> 3

It seems very fragile to me as a way of communicating what’s going on.
There are two ways of saying “This takes no arguments”, and what they
mean depends on the Proc/proc distinction. I guess this is old news
– it’s just another twist, and one I hadn’t noticed before, on that
whole area.

(Matz, please proceed with the removal of ‘proc’ :slight_smile:

David

46

Hi –

On Wed, 23 Nov 2005, Jeff W. wrote:

Anyways, You could seperate them if you didn’t want them to look like or …
like …

{ | | [] } … although that’s kinda ugly to me.

No argument there :slight_smile:

I’d be just as happy to use the new block syntax ->{ [] } … when is that
going to see the light of day ???

I think I’m not alone is saying: hopefully never :slight_smile: Anyway, you can
just do:

Hash.new { [] }

It’s a pretty common idiom, and the block is unambiguously a block.
(If it were a hash argument it would have to be in parentheses.)

David

47

Hi –

On Wed, 23 Nov 2005, Christophe G. wrote:

@attributes << a2
end
difficult to read).

The short answer is “yes”. The long asnwer is that both are ways to add a
singleton method to a particular object, @attributes in this case. The first
one is just shorter and practical when you want to create just one singleton
method. But it’s mostly a matter of style.

There’s also a (usually not too important) difference involving the
scope of constants. The << version will see constants in the
singleton class, whereas the def obj.meth version won’t:

obj = Object.new

A = 1

class << obj
A = 2
def x
puts A
end
end

def obj.y
puts A
end

obj.x # 2
obj.y # 1

David

48

Selon “ako…” [email protected]:

this is something i have never seen. would you explain the ‘def’ line
above? is this the same as class << @attributes; def << …; end ?

If I understand correctly you are asking whether:

def @attributes.<<(obj)
…
end

is the same as:

class << @attributes
def <<(obj)
…
end
end

(I rewrote them because the clash of << as syntax and << as method made
it a bit
difficult to read).

The short answer is “yes”. The long asnwer is that both are ways to add
a
singleton method to a particular object, @attributes in this case. The
first
one is just shorter and practical when you want to create just one
singleton
method. But it’s mostly a matter of style.

Christophe G…

http://rainbow.conlang.free.fr

It takes a straight mind to create a twisted conlang.

49

On Nov 22, 2005, at 5:45 PM, Bill K. wrote:

@attributes = Hash.new {|h,k| h[k] = Array.new}

Hey, thanks for that! I had no idea that the block form of Hash
creation had block arguments. Sure it’s in ‘ri’, but who looks there? :wink:

I often see people suggesting:
Hash.new{ [] }
without realizing that this doesn’t set the value on the hash, just
returns a blank array. I’ve never been able to use the block
constructor syntax because it was so useless (because I also didn’t
know that <<= was a valid compound method).

foo = Hash.new{ [] }
foo[:bar] << 1
foo[:foo] << 2
foo[:bar] << 3
p foo
#=>{}

foo = Hash.new{ |h,v| h[v]=[] }
foo[:bar] << 1
foo[:foo] << 2
foo[:bar] << 3
p foo
#=>{:bar=>[1, 3], :foo=>[2]}

foo = Hash.new{ [] }
foo[:bar] <<= 1
foo[:foo] <<= 2
foo[:bar] <<= 3
p foo
#=>{:bar=>[1, 3], :foo=>[2]}

50

David A. Black wrote:

now ( heh, need to get that into the rubyscore app )… for my

It’s a pretty common idiom, and the block is unambiguously a block.
(If it were a hash argument it would have to be in parentheses.)

Note though that this idiom will most likely lead to surprising results
wrt the OP’s requirement. :slight_smile:

Cheers

robert