Question about magic enumerators in > 1.8

Ruby
1

Hi –

Can someone jog my memory, and/or enlighten me, as to what a case
would be where it’s useful to have:

array.map

return an Enumerator? I can’t seem to come up with an example where:

array.map.anything

is different from

array.anything

Thanks –

David

2

On Jul 9, 2006, at 9:03 AM, [email protected] wrote:

is different from

array.anything

Thanks –

Well, you can use it to roll the oft-requested map_with_index():

array.each_with_index.map { |obj, i| … }

That’s not a map() example though, so maybe not what you wanted.

James Edward G. II

3

Hi –

On Sun, 9 Jul 2006, James Edward G. II wrote:

array.each_with_index.map { |obj, i| … }

That’s not a map() example though, so maybe not what you wanted.

Right, it isn’t :slight_smile: I’m still looking for a map example.

David

4

On Jul 9, 2006, at 10:36 AM, [email protected] wrote:

array.map

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Contrived example: I know a method I’m about to call iterates thru me
with each doing something. It’s the last thing it does and what the
results of the thing it does rather than myself at the end:

some_method(array.map)

Ok so it’s a REALLY contrived example.

5

“d” == dblack [email protected] writes:

d> return an Enumerator? I can’t seem to come up with an example where:

d> array.map.anything

d> is different from

d> array.anything

moulon% ./ruby -e ‘[12].map.with_index {}’
moulon%

moulon% ./ruby -e ‘[12].with_index {}’
-e:1: undefined method `with_index’ for [12]:Array (NoMethodError)
moulon%

p.s.:
:-))))

–

Guy Decoux

6

Hi –

On Mon, 10 Jul 2006, Christian N. wrote:

array.map.anything

is different from

array.anything

names.map { |x| x.size }.max, and you don’t need an immediate array.

That’s not an example of what I’m asking about, though. There’s no
enumerator returned there.

David

7

[email protected] writes:

is different from

array.anything

names.map { |x| x.size }.max, and you don’t need an immediate array.