Why splat variable couldn’t take in the below two code the “range” ->
(1…8)?
means why a gives []?
*a,b = (1…8)
#=> 1…8
b
#=> 1…8
a
#=> []
means why b gives []?
a,*b = (1…8)
#=> 1…8
a
#=> 1…8
b
#=> []
Splat is an array operation, Range is not an array.
there:
*a,b = *(1…8)#=> [1, 2, 3, 4, 5, 6, 7, 8]
On Saturday 23 February 2013 Love U Ruby wrote
#=> []
Posted via http://www.ruby-forum.com/.
In both case, the right hand side of the assignment is a single object.
When
this happens, the object can be assigned to only one of the variables on
the
left hand side of the assignment. In your first example, the * before a
tells
that a can contain any number of values (including no values). So ruby
assign
the only availlable value (the range) to b and assign an empty array to
a. In
the second case, it’s the opposite.
Arrays and objects responding to #to_ary are an exception to the rule,
as they
are automatically distributed among the variables:
*a,b = (1…8).to_a
#=> [1,2,3,4,5,6,7,8]
b
#=> 8
a
#=> [1,2,3,4,5,6,7]
You can obtain what you want without explicitly converting the range to
an
array using the splat operator:
a,b=(1…8)
#=> [1,2,3,4,5,6,7,8]
b
#=> 8
a
#=> [1,2,3,4,5,6,7]
Stefano
On Sat, 23 Feb 2013 07:08:05 +0100, Matthew K.
[email protected] wrote:
Splat is an array, Rang is not an array.
Matthew, what? This doesn’t even make sense.
On Sat, Feb 23, 2013 at 9:52 AM, Bartosz Dziewoński
[email protected] wrote:
On Sat, 23 Feb 2013 07:08:05 +0100, Matthew K. [email protected]
wrote:Splat is an array, Rang is not an array.
Matthew, what? This doesn’t even make sense.
It does, because
irb(main):004:0> Range.instance_method :to_ary
NameError: undefined method to_ary' for class Range’
from (irb):4:in instance_method' from (irb):4 from /usr/bin/irb:12:in ’
and, as our friend would have learned a few days back if he followed
the advice to use set_trace_func to learn what’s going on
irb(main):015:0> o = Object.new
=> #Object:0x802a7a80
irb(main):016:0> def o.to_ary; [1,2,3,4] end
=> nil
irb(main):017:0> a, *b, c = o
=> #Object:0x802a7a80
irb(main):018:0> a
=> 1
irb(main):019:0> b
=> [2, 3]
irb(main):020:0> c
=> 4
Cheers
robert
On Sat, 23 Feb 2013 13:44:25 +0100, Matthew K.
[email protected] wrote:
I know, I know. I wasn’t paying attention while typing and didn’t realise
how bad it was. I edited the post immediately on the forum interface, but
apparently the mailing list version got sent first.I think it now says something like “Splat is an array operation, Range is
not an array.”
But you can splat a range?
irb(main):004:0> a, b, c = *0…2
=> [0, 1, 2]
irb(main):005:0> a
=> 0
irb(main):006:0> b
=> 1
irb(main):007:0> c
=> 2
Are we misunderstanding each other?
On 23 February 2013 18:52, Bartosz Dziewoński [email protected]
wrote:
On Sat, 23 Feb 2013 07:08:05 +0100, Matthew K. [email protected]
wrote:Splat is an array, Rang is not an array.
Matthew, what? This doesn’t even make sense.
I know, I know. I wasn’t paying attention while typing and didn’t
realise
how bad it was. I edited the post immediately on the forum interface,
but
apparently the mailing list version got sent first.
I think it now says something like “Splat is an array operation, Range
is
not an array.”
On Sat, Feb 23, 2013 at 2:00 PM, Bartosz Dziewoński
[email protected] wrote:
Are we misunderstanding each other?
You created an explicit implicit Array conversion by using “*” on the
right side. The point Matthew and I were trying to make is that you
cannot do the same with a range without the splat operator on the
right side:
irb(main):004:0> a, b, c = 0…2
=> 0…2
irb(main):005:0> a
=> 0…2
irb(main):006:0> b
=> nil
irb(main):007:0> c
=> nil
Whereas with an Array you can:
irb(main):012:0> a, b, c = [0, 1, 2]
=> [0, 1, 2]
irb(main):013:0> a
=> 0
irb(main):014:0> b
=> 1
irb(main):015:0> c
=> 2
Cheers
robert
Ah. Yes, this makes sense.