Ruby Koan 151 raising exceptions

user_132331 0
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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 'triangle.rb'
require 'triangle.rb'

class AboutTriangleProject2 < EdgeCase::Koan
  # The first assignment did not talk about how to handle errors.
  # Let's handle that part now.
  def test_illegal_triangles_throw_exceptions
    assert_raise(TriangleError) do triangle(0, 0, 0) end
    assert_raise(TriangleError) do triangle(3, 4, -5) end
    assert_raise(TriangleError) do triangle(1, 1, 3) end
    assert_raise(TriangleError) do triangle(2, 4, 2) end
 end
end

Then in triangle.rb we have:

def triangle(a, b, c)
  # WRITE THIS CODE
  if a==b && a==c
    return :equilateral
  end
  if (a==b && a!=c) || (a==c && a!=b) || (b==c && b!=a)
    return :isosceles
  end
  if a!=b && a!=c && b!=c
    return :scalene
  end
  if a==0 && b==0 && c==0
    raise new.TriangleError
  end



end

# Error class used in part 2.  No need to change this code.
class TriangleError < StandardError

end

I am beyond confused - any help at all would be much appreciated!

EDIT: To complete this koan, I need to put something in the TriangleError class - but I have no idea what

UPDATE: Here is what the koan karma thing is saying:

<TriangleError> exception expected but none was thrown.
geometry ruby
38 Answers

You don't need to modify the Exception. Something like this should work;

def triangle(*args)
  args.sort!
  raise TriangleError if args[0] + args[1] <= args[2] || args[0] <= 0
  [nil, :equilateral, :isosceles, :scalene][args.uniq.length]
end
user_6803160

You could also try to instance the exception with:

raise TriangleError.new("All sides must be greater than 0") if a * b * c <= 0
user_12774010

My solution, I think it's one of the more readable ones:

def triangle(a, b, c)
  a, b, c = [a, b, c].sort
  if a <= 0 or c >= a + b
    raise TriangleError
  end
  case [a, b, c].uniq.length
  when 1
    :equilateral
  when 2
    :isosceles
  when 3
    :scalene
  end
end
user_7865800

This is my solution:-

def triangle(a, b, c)
  if a <= 0 || b <= 0 || c <= 0 || a + b <= c  || a + c <= b ||  b + c <= a
    raise TriangleError
  elsif (a == b) &&( a==c) && (b==c)
    return :equilateral
  elsif (a==b) || (b==c) || (a==c)
    return :isosceles
  else
    return :scalene
  end
end

Hope it helps.

user_62336430

SIMPLEST SOLUTION!

  def triangle(a, b, c)
  #This would check for if the numbers are negative or 0.
  if a <= 0 || b <= 0 || c <= 0 
    raise TriangleError
  end
  #This would check if the two sides of a triangle are greater than the remaining side.
  if a + b <= c  || a + c <= b ||  b + c <= a
    raise TriangleError
  end 

  if a == b && b = c
    :equilateral
  elsif a == b || a == c || b == c 
    :isosceles
  else 
    :scalene
  end
end

Thanks to all the beautiful people for their answer I have checked them all and I would say no need to change the TriangleError code. we need to check for invalid triangles and raise the error if the triangle is not.

user_142673110

The triangle.rb file need these update to work.

def triangle(a, b, c)
    # If length is Less Then or equal to 0 the triangle not possible
    # it raise error. If the length of any two sum is less or equal to other-
    # Again the triangle not possible.
    raise TriangleError if (a <= 0 || b <= 0 || c <= 0) || (a+b <= c || b+c <= a || c+a <= b)  

    # If the size of each equal its Equilateral Triangle.       
    return :equilateral if (a == b && a == c)

    # If any two lenght is equal than it Isosceles Triangle.
    return :isosceles if (a == b || b == c || a == c)

    # If each lenght is different than its Scalene Triangle.
    return :scalene if (a != b) && (b != c) && (a != c)
end  

class TriangleError < StandardError
end
user_36070510
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