I guess it’s a precedence issue. ‘<<’ is a method in the Array class.
‘+=’ is not.
The difference is that << is a method, += is an assignment. (a ||= [])
returns an object, on which you can call a method, but you can’t assign
to. You can only assign to the a variable itself, which (a ||= []) is
not. I guess.
I guess it’s a precedence issue. ‘<<’ is a method in the Array class.
‘+=’ is not.
No, it’s not a precedence issue. Btw, you are comparing apples and
oranges here: += and << are not equivalent (see also further below):
irb(main):001:0> a=%w{foo bar}
=> [“foo”, “bar”]
irb(main):002:0> b=a.dup
=> [“foo”, “bar”]
irb(main):003:0> c=a.dup
=> [“foo”, “bar”]
irb(main):004:0> b << a
=> [“foo”, “bar”, [“foo”, “bar”]]
irb(main):005:0> c += a
=> [“foo”, “bar”, “foo”, “bar”]
<< adds the whole Array as one object while += “appends” the Array.
You rather want Array#concat.
The difference is that << is a method, += is an assignment. (a ||= [])
returns an object, on which you can call a method, but you can’t assign
to. You can only assign to the a variable itself, which (a ||= []) is
not. I guess.
Exactly: the expression (a||=[]) is not an lvalue, i.e. cannot
assigned to. But you can do
( a ||= [] ).concat [ 1, 2, 3, 4 ]
Simon, please also keep in mind that += and << have different
semantics. += will create a new Array while << appends to the current
one.
The difference between the two is exactly why I wanted to use += and
not <<. I want to add many arrays to one big one and not have to use
the extra step of Array#flatten at the end.
The difference between the two is exactly why I wanted to use += and
not <<. I want to add many arrays to one big one and not have to use
the extra step of Array#flatten at the end.
That’s why you should be using #concat (more efficient) unless you do
not want to modify the original array. Read the solutions properly!