Changing enum_obj

Anyway to change an Enumerator’s enum_obj in place? Enumerator doesn’t
seem to support the #collect! method.

T.

On Jun 23, 2007, at 11:07 PM, Trans wrote:

Anyway to change an Enumerator’s enum_obj in place? Enumerator doesn’t
seem to support the #collect! method.

Knowing that an object is Enumerable doesn’t tell you anything about
how to edit it, so there’s no way Enumerable could logically support
destructive operations.

James Edward G. II

On Jun 24, 12:26 am, James Edward G. II [email protected]
wrote:

On Jun 23, 2007, at 11:07 PM, Trans wrote:

Anyway to change an Enumerator’s enum_obj in place? Enumerator doesn’t
seem to support the #collect! method.

Knowing that an object is Enumerable doesn’t tell you anything about
how to edit it, so there’s no way Enumerable could logically support
destructive operations.

Ah, of course.

Thanks,
T.

Well, I might as well bring up the reason I asked about enum_obj…

Spending some time improving Facets’ Elementor class concept and
#every method, I find this possible utter simplification:

class Enumerable::Enumerator
def method_missing(sym, *args, &blk)
self.class.new(collect{ |e| e.send(sym, *args, &blk) })
end
end

Example:

a = [1,2,3]
e = a.to_enum
e += 3
e *= 2
e.to_a #=> [8,10,11]

T.

On 6/24/07, Trans [email protected] wrote:

Example:

a = [1,2,3]
e = a.to_enum
e += 3
e *= 2
e.to_a #=> [8,10,11]

T.

Apart the magic dot notation that is exactly what I am doing in
Labrador.
Well I cannot expect blocks in this way as they have the original
purpose and are sent to map.

module Enumerable

alias_method :__map_l1, :map

The behavior of map {…} is unchanged.

map(arg1, *rest) simply is translated to map{ |ele| ele.send(arg1,

*rest) }

map(arg1, *rest){…} is translated to map{|ele|

ele.send(arg1,*rest}.map{…}

map without any arguments creates a Dispatcher Proxy that will

dispatch all messages

to the elements of the receiver.

All the following expressions evaluate therefore to the same result:

ary=[*0…9]

ary.map{ |x| x + 1}

ary.map(:succ)

ary.map.succ

ary.map(:+, 1)

ary.map + 1

def map *args, &blk
return Labrador::Dispatcher.new( self, :map ) if args.empty? &&
blk.nil?
return __map_l1( &blk ) if args.empty?
return __map_l1 { |x| x.send( *args ) } if blk.nil?
__map_l1 { |x| x.send( *args ) }.__map_l1( &blk )
end # def map *args, &blk

end # module Enumerable

Robert

On Jun 24, 4:15 am, “Robert D.” [email protected] wrote:

def method_missing(sym, *args, &blk)

e.to_a #=> [8,10,11]

ary.map{ |x| x + 1}

end # module Enumerable

Ah, so you overloaded #map with this functionality. That’s similar to
what I had done, but I used a different method name, #every, which is
defined:

module Enumerable
def every
@_functor_every ||= Functor.new do |op,*args|
self.collect{ |a| a.send(op,*args) }
end
end
end

Both are limited in one common respect. They can’t be chained along
without repeated invocation, eg. it’s not

[1,2,3].map * 6 + 4

We have to do:

([1,2,3].map * 6).map + 4

Not quite as bad for #map, as opposed to #every, being shorter, but it
would still be nice to chain. Of course, to do that one must
explicitly #to_a the final result per my original Enumerator example.

One thing you might want to consider, Ruby 1.9+ returns an Enumerator
for #map without a block, could pose some compatibility issues in the
future. Though, I have to admit I’m not quite sure what a #map based
Enumerator is good for – when you run #each on it, it acts like
#map !!!

T.

That is even broken in Labrador, so much work to do :frowning:

irb(main):001:0> require ‘labrador’
=> true
irb(main):002:0> [1,2,3].map + 2
=> [3, 4, 5]
irb(main):003:0> [1,2,3].map + 2 * 3
=> [7, 8, 9] *** Arrrgh

I think that’s right, * takes precedence. So you’re getting the result
of ‘+ 6’.

T.

On 6/24/07, Trans [email protected] wrote:

#every method, I find this possible utter simplification:
e = a.to_enum
module Enumerable

return __map_l1 { |x| x.send( *args ) } if blk.nil?
__map_l1 { |x| x.send( *args ) }.__map_l1( &blk )

end # def map *args, &blk

end # module Enumerable

Ah, so you overloaded #map with this functionality. That’s similar to
what I had done, but I used a different method name, #every, which is
defined:
Facets is great but Labrador is mine, what does that mean: I have the
luxury to do things that scale badly and break compatibility, – I
have to make the documentation clear about this in the next version.
Facets is a General Purpose Library and cannot afford that luxury, so
it is very clear why you have #every – a tempting idea not to
overload map, even in an experimental package as my dog package. Yet
another advantage, I just change the name, nobody can complain…
OTH I am surprised that #every corresponds to #map, from its naming on
would say it should correspond to #each.

module Enumerable
def every
@_functor_every ||= Functor.new do |op,*args|
self.collect{ |a| a.send(op,*args) }
end
end
end

I gotta look at your Functors again, maybe I can steal a little bit from
you;)

Both are limited in one common respect. They can’t be chained along
without repeated invocation, eg. it’s not

[1,2,3].map * 6 + 4
That is even broken in Labrador, so much work to do :frowning:

irb(main):001:0> require ‘labrador’
=> true
irb(main):002:0> [1,2,3].map + 2
=> [3, 4, 5]
irb(main):003:0> [1,2,3].map + 2 * 3
=> [7, 8, 9] *** Arrrgh

We have to do:

([1,2,3].map * 6).map + 4

Not quite as bad for #map, as opposed to #every, being shorter, but it
would still be nice to chain. Of course, to do that one must
explicitly #to_a the final result per my original Enumerator example.

One thing you might want to consider, Ruby 1.9+ returns an Enumerator
for #map without a block, could pose some compatibility issues in the
future.
That is a good thing, and thanks for pointing it out, looking for a
different name for #map now :wink:
Though, I have to admit I’m not quite sure what a #map based
Enumerator is good for – when you run #each on it, it acts like
#map !!!

T.

Cheers
Robert

On Jun 24, 12:32 am, Trans [email protected] wrote:

destructive operations.

Ah, of course.

Wait. Yes, the #collect! method isn’t going to fly, but if I could
just reassign enum_object – that would actually better.

T.

On Jun 24, 7:05 am, “Robert D.” [email protected] wrote:

Facets is great but Labrador is mine, what does that mean: I have the
luxury to do things that scale badly and break compatibility, – I
have to make the documentation clear about this in the next version.
Facets is a General Purpose Library and cannot afford that luxury, so
it is very clear why you have #every – a tempting idea not to
overload map, even in an experimental package as my dog package. Yet
another advantage, I just change the name, nobody can complain…
OTH I am surprised that #every corresponds to #map, from its naming on
would say it should correspond to #each.

Yes, but #each is taken too :wink: I though about #each? though.

module Enumerable
def every
@_functor_every ||= Functor.new do |op,*args|
self.collect{ |a| a.send(op,*args) }
end
end
end

I gotta look at your Functors again, maybe I can steal a little bit from you;)

Basic Functor is easy:

class Functor
private *instance_methods
def initialize(&function)
@function = function
end
def method_missing(sym,*args,&blk)
@function.call(sym,*args,&blk)
end
end

Facets’ is a little more fleshed out than that, but that’s all one
needs. And I still think it worthy of inclusion in Ruby’s standard
library.

That is a good thing, and thanks for pointing it out, looking for a
different name for #map now :wink:
Though, I have to admit I’m not quite sure what a #map based> Enumerator is good for – when you run #each on it, it acts like

#map !!!

I may have a solution for you:

require ‘enumerator’

class Enumerable::Enumerator
def method_missing(sym,*args,&blk)
each{ |x| x.send(sym,*args,&blk) }
end
end

With 1.9+ you’ll get what you want (mostly). For 1.8, you just need to
override map to return the Enumerator (just like 1.9 does). Btw, if
you do the same for #select:

[1,2,3].select < 2 #=> [1]

Oh, I am soooo tempted to put this in Facets.

T.

I think that’s right, * takes precedence. So you’re getting the result
of ‘+ 6’.
Oops , thx Tom.

This forum is not affiliated to the Ruby language, Ruby on Rails framework, nor any Ruby applications discussed here.

| Privacy Policy | Terms of Service | Remote Ruby Jobs