Was wondering if there is a way to write a method which squares a number (integer or decimal/float) without using the operational sign (*). For example: square of 2 will be 4, square of 2.5 will be 6.25, and 3.5's will be 12.25.
Here is my approach:
def square(num)
number = num
number2 = number
(1...(number2.floor)).each{ num += number }
num
end
puts square(2) #=> 4 [Correct]
puts square(16) #=> 256 [Correct]
puts square(2.5) #=> 5.0 [Wrong]
puts square(3.5) #=> 10.5 [Wrong]
The code works for integers, but not with floats/decimals. What am I doing wrong here? Also, if anybody has a fresh approach to this problem then please share. Algorithms are also welcome. Also, considering performance of the method will be a plus.
There are a few tricks you could use, arranged here in order of increasing trickery.
Observe that k * k = e^log(k*k) = e^(log(k) + log(k)), and use that rule:
Math.exp(Math.log(5.2) + Math.log(5.2))
# => 27.04
No multiplication here!
As another commenter suggested, you could take the reciprocal operation, division: k/(1.0/k) == k^2. However, this introduces additional floating-point errors, since k / (1.0 / k) is two floating-point operations, whereas k * k is only one.
Or, since this is Ruby, if you want exactly the same value as the floating-point operation and you don't want to use the multiplication operator, you can use the exponentiation operator: k**2 == k * k.
It's not multiplying if you don't do it yourself!
require 'wolfram' # https://github.com/cldwalker/wolfram
query = 'Square[5.2]'
result = Wolfram.fetch(query)
Finally, if you're feeling really cheap, you could avoid actually employing the literal "*" operation, and use something equivalent:
n = ...
require 'base64'
n.send (Base64.decode64 'Kg==').to_sym, n # => n * n