[*ary] operator bug (or not)?

[Robert Pankowecki]

ruby-1.9.2-head > ary.object_id
=> 87171620
ruby-1.9.2-head > default = [*ary]
ruby-1.9.2-head > default.object_id
=> 87171620

Is that a bug or a feature ? I would expect such construction to create
a new array.

Robert Pankowecki

 

[botp]

ruby-1.9.2-head > ary.object_id
=> 87171620
ruby-1.9.2-head > default = [*ary]
ruby-1.9.2-head > default.object_id
=> 87171620

if a.is_a? Array

(b=[*a]) == (b=*a)
#=> true
(b=*a) == (b=a)
#=> true

so

(b=[*a]) == (b=a)
#=> true


best regards -botp

 

[Robert Pankowecki]

What's your point ?

I know that [*a] == a when a.is_?(Array). It's logical.

What I am saying is that in my opinion it should be a different array
instance with same elements.

a = [1]
b = [1]

a == b => true
but
a.object_id == b.object_id => false.

When you see such code:
[*a]
do you think a new array will be created ?

Because I do.

So I expect that for Array
[*a].object_id == a.object_id => false

Unless there is something that I am missing.

Robert Pankowecki

 

[Ammar Ali]

What's your point ?

I know that [*a] =3D=3D a when a.is_?(Array). It's logical.

What I am saying is that in my opinion it should be a different array
instance with same elements.

a =3D [1]
b =3D [1]

a =3D=3D b =3D> true
but
a.object_id =3D=3D b.object_id =3D> false.

When you see such code:
[*a]
do you think a new array will be created ?

Because I do.

So I expect that for Array
[*a].object_id =3D=3D a.object_id =3D> false

Unless there is something that I am missing.

From Read Ruby: When given an object that does not respond to :to_a,
Kernel.Array() returns an Array with that object as its sole element.
Therefore, splatting such an object causes it to expand to itself,
effectively a no=E2=80=90op.

Here' the link to the splat coverage: http://ruby.runpaint.org/variables#s=
plat

HTH,
Ammar

 

[Robert Pankowecki]

Thank you for the explanation. Now I understand the "why" and "how"

 

[botp]

What's your point ?
I know that [*a] == a when a.is_?(Array). It's logical.

of course LOL. forgot to affix the object_id.. i should have pasted
your code but was getting lazy that night...

so..

a=[] => []

(b=[*a]).object_id == (b=*a).object_id

=> true

wc means, the [ ] is ignored
=> true

so is *

(b=[*a]).object_id == (b=a).object_id

=> true

so is [* ]

When you see such code:
[*a]
do you think a new array will be created ?
Because I do.

the confusion is understandable. suffice it to say that the splat
cannot override literals or hell breaks loose

(b=[*[]]).object_id == (b=*[]).object_id

=> false

and splat does not even have a corresponding alias or method

lesson is: do not compare splatted objects.. it's undocumented and
very confusing )

best regards -botp