Ruby Koan 151 raising exceptions

Question

I\'m going through the ruby koans, I\'m on 151 and I just hit a brick wall.

Here is the koan:

# You need to write the triangle method in the file \'trian         


        

Answer 1

I ended up with this code:

def triangle(a, b, c)
    raise TriangleError, "impossible triangle" if [a,b,c].min <= 0
    x, y, z = [a,b,c].sort
    raise TriangleError, "no two sides can be < than the third" if x + y <= z

    if a == b && b == c # && a == c # XXX: last check implied by previous 2
        :equilateral
    elsif a == b || b == c || c == a
        :isosceles
    else
        :scalene
    end
end 

I don't like the second condition/raise, but I'm unsure how to improve it further.