Array range values assignment

Ruby
1

a = [“A”,“A”,“A”,“A”,“A”, “A”,“A”,“A”,“A”,“A”]
a[3…7] = “B”

QUESTION:
after code executes a = [“A”, “A”, “A”, “B”, “A”, “A”, “A”]
what should I do to make a = [“A”, “A”, “A”, “B”, “B”, “B”, “B”, “A”,
“A”, “A”]

2

Just
a[3…7] = [‘B’,‘B’,‘B’,‘B’].

Works at least in 1.9.2.

2011/3/18 Ruby F. [email protected]

3

I understand that :slight_smile:

But I need some universal way to change values of arrays with 10+
elements

4

Found way:

b = []
a[3…7].size.times do b.push(“B”) end
a[3…7] = b

is there anything simplier?

5

Jeremy,

Thank you! :slight_smile: It’s very nice :))

6

On 3/18/2011 10:22, Ruby F. wrote:

Found way:

b = []
a[3…7].size.times do b.push(“B”) end
a[3…7] = b

is there anything simplier?

Not necessarily any simpler, but perhaps a bit more efficient:

3…7.each { |i| a[i] = “B” }

Wrap it up into a nice method:

class Array
def replace_range_with(range, replacement)
range.each { |i| self[i] = replacement }
self
end
end

a = [“A”, “A”, “A”, “A”, “A”]
a.replace_range_with(2…4, “B”) #=> [“A”, “A”, “B”, “B”, “A”]

-Jeremy

7

You can use the fill method in the Array class

e.g from the Ruby docs

a.fill(“z”, 2, 2) #=> [“x”, “x”, “z”, “z”]
a.fill(“y”, 0…1) #=> [“y”, “y”, “z”, “z”]

Please refer to the Ruby docs for other ways to use the fill method

http://railsapi.com/doc/ruby-v1.9.2/classes/Array.html#M000097

8

On Fri, Mar 18, 2011 at 11:31 PM, Jeremy B. [email protected] wrote:

def replace_range_with(range, replacement)
range.each { |i| self[i] = replacement }
self
end
end
a = [“A”, “A”, “A”, “A”, “A”]
a.replace_range_with(2…4, “B”) #=> [“A”, “A”, “B”, “B”, “A”]

in some cases, specifying the starting and the length may be also
handy, eg,

a=[“A”]*10
#=> [“A”, “A”, “A”, “A”, “A”, “A”, “A”, “A”, “A”, “A”]

a[3,4]=[“B”]*4
#=> [“B”, “B”, “B”, “B”]

a
#=> [“A”, “A”, “A”, “B”, “B”, “B”, “B”, “A”, “A”, “A”]

and ff jeremy’s wrapping,

class Array
def replacex start,length, item
self[start,length]=[item]*length
end
end
#=> nil

a=[“A”]*10
#=> [“A”, “A”, “A”, “A”, “A”, “A”, “A”, “A”, “A”, “A”]

a.replacex 3, 4,“B”
#=> [“B”, “B”, “B”, “B”]

a
#=> [“A”, “A”, “A”, “B”, “B”, “B”, “B”, “A”, “A”, “A”]

best regards -botp