gistfile1.txt

require 'prime'

def gap(g, m, n)
    (m..n).each{ |i| 
    #puts "i: #{i} i+g: #{i+g}"
    if Prime.prime?(i) && Prime.prime?(i+g)
    	puts "primes found, stepping"
    	(i+1..i+g-1).each{ |j| 
        #puts "i: #{i} j: #{j}"
      	if Prime.prime?(j)
            puts "inner prime found, abort"
            return nil
        end
      }
      return [i, i+g]
    end
  }
  return nil
end

TESTS:
Test.assert_equals(gap(10,300,400), [337, 347])

OUTPUT
i: 300 i+g: 310
i: 301 i+g: 311
i: 302 i+g: 312
i: 303 i+g: 313
i: 304 i+g: 314
i: 305 i+g: 315
i: 306 i+g: 316
i: 307 i+g: 317
primes found, stepping
i: 307 j: 308
i: 307 j: 309
i: 307 j: 310
i: 307 j: 311
inner prime found, abort
Expected: [337, 347], instead got: nil