Hi,
I’m new to ruby, and I am trying to add all the natural numbers below
one thousand that are multiples of 3 or 5. (exercise from ProjectEuler)
Here’s my code:
class Array
def sumNumbers
sum = 0
self.each_with_index { |n, i|
if ((self[i] % 3) == 0 || (self[i] % 5) == 0)
sum += self[i]
end
}
sum
end
end
numbers = [1…1000]
print "Sum of natural numbers till 1000 that are multiples of 3 or 5 is
" + numbers.sumNumbers
When I try to execute this, I get this error:
SumOfMults.rb:5:in block in sumNumbers': undefined method
%’ for
1…1000:Range
(NoMethodError)
from SumOfMults.rb:4:in each' from SumOfMults.rb:4:in
each_with_index’
from SumOfMults.rb:4:in sumNumbers' from SumOfMults.rb:14:in
’
Not sure how self[i] is actually treated as a Range. Can you please let
me know what’s wrong in my code?
Thanks,
Mouli
numbers = [1…1000]
In your code, numbers is an array with a single element. That single
element is a range of numbers from 1…1000. Instead, don’t you want
numbers to be an array like [1, 2, 3, 4, 5, …, 999, 1000]? You can
create this array by
numbers = Array.new(1000) { |i| i+1 }
–Alex
On Tue, May 4, 2010 at 12:59 PM, Chandramouli Parasuraman
[email protected] wrote:
I would be more rubymatic here 
1000.times.inject{ | sum_so_far, next_number |
if (next_number % 3).zero? || (next_number % 5).zero?
sum_so_far + next_number
else
sum_so_far
end
}
It might be exaggerated to use the implicit form of inject just
because the first value is zero (it will be passed to sum_so_far in
the first iteration)
inject(0){ | sum_so_far, next_number |
}
might have been more readable
HTH
R.
On Tue, May 4, 2010 at 1:37 PM, Brian C. [email protected]
wrote:
numbers = (1…1000).to_a
or even [*1…1000] ( remark that 1000 must not be in the solution here
).
However I feel it is completely inadequate to the solution to create
an array of 999 numbers.
R.
(1…1000).select{|n| n % 3 == 0 or n % 5 == 0}.inject{|sum,n| sum + n }
Great, now I understand. Works fine now with both Array.new(1000) {|i|
i+1} and the inject.
Thanks everyone.