CODEWITHSUNDEEP
ruby
wanderingnowhere
wanderingnowhere

Reputation: 45

2 to the power of multiples numbers

I'm trying to create a method that takes a number and then puts every number between that and 0 as an exponent to the number 2.

2^0 = 1

2^1 = 2

2^2 = 4

2^3 = 8

2^4 = 16

This is as far as I've gotten. . .

def powers_of_two(n)
   n.map { |x| 2 ** (0..x) }
end

I believe I'm not far off in my attempt.

Upvotes: 1

Views: 144

Answers (3)

Cary Swoveland
Cary Swoveland

Reputation: 110725

As we are dealing with powers of 2, try this bit-shifting method. (I assume the given number n is non-negative.)

def po2(n)
  (0..n).each { |i| puts 1 << i }
end 

po2(7)
1
2
4
8
16
32
64
128

See Integer#<< and possibly this tutorial.

One could alternatively create a proc.

po2 = Proc.new { |n| (0..n).each { |i| puts 1 << i } }
  #=> #<Proc:0x00007f91a5222bb0 <main>:0>

po2(7)
1
2
4
8
16
32
64
128

Upvotes: 3

Stefan
Stefan

Reputation: 114208

You can build an enumerator that generates the numbers via Enumerator.produce:

powers = Enumerator.produce(1) { |i| i * 2 }

powers.take(5)
#=>[1, 2, 4, 8, 16]

The block generates each number based on the previous one, starting at 1.

The same works for bit-shifting:

powers = Enumerator.produce(1) { |i| i << 1 }

powers.take(5)
#=>[1, 2, 4, 8, 16]

Upvotes: 4

spickermann
spickermann

Reputation: 106972

For example, like this:

def power_of_two(n) = (0..n).each { puts 2 ** _1 }     
power_of_two(4)
#=> 1
    2                                       
    4                                       
    8                                       
    16

Upvotes: 4

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