Determine if a triangle is equilateral, isosceles, or scalene.
An equilateral triangle has all three sides the same length.
An isosceles triangle has at least two sides the same length. (It is sometimes specified as having exactly two sides the same length, but for the purposes of this exercise we'll say at least two.)
A scalene triangle has all sides of different lengths.
For a shape to be a triangle at all, all sides have to be of length > 0, and the sum of the lengths of any two sides must be greater than or equal to the length of the third side. See Triangle Inequality.
The case where the sum of the lengths of two sides equals that of the third is known as a degenerate triangle - it has zero area and looks like a single line. Feel free to add your own code/tests to check for degenerate triangles.
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The Ruby Koans triangle project, parts 1 & 2 http://rubykoans.com
(* triangle - 1.2.1 *) open Base open OUnit2 open Triangle let ae exp got _test_ctxt = assert_equal exp got ~printer:Bool.to_string let equilateral_triangle_tests = [ "all sides are equal" >:: ae true (is_equilateral 2 2 2); "any side is unequal" >:: ae false (is_equilateral 2 3 2); "no sides are equal" >:: ae false (is_equilateral 5 4 6); "all zero sides is not a triangle" >:: ae false (is_equilateral 0 0 0); ] let isosceles_triangle_tests = [ "last two sides are equal" >:: ae true (is_isosceles 3 4 4); "first two sides are equal" >:: ae true (is_isosceles 4 4 3); "first and last sides are equal" >:: ae true (is_isosceles 4 3 4); "equilateral triangles are also isosceles" >:: ae true (is_isosceles 4 4 4); "no sides are equal" >:: ae false (is_isosceles 2 3 4); "first triangle inequality violation" >:: ae false (is_isosceles 1 1 3); "second triangle inequality violation" >:: ae false (is_isosceles 1 3 1); "third triangle inequality violation" >:: ae false (is_isosceles 3 1 1); ] let scalene_triangle_tests = [ "no sides are equal" >:: ae true (is_scalene 5 4 6); "all sides are equal" >:: ae false (is_scalene 4 4 4); "two sides are equal" >:: ae false (is_scalene 4 4 3); "may not violate triangle inequality" >:: ae false (is_scalene 7 3 2); ] let () = run_test_tt_main ( "triangle tests" >::: List.concat [ equilateral_triangle_tests; isosceles_triangle_tests; scalene_triangle_tests; ] )
let validate a b c = a+b > c && b+c > a && c+a > b let is_equilateral a b c = validate a b c && a = b && b = c let is_isosceles a b c = validate a b c && (a = b || b = c || c = a) let is_scalene a b c = validate a b c && a <> b && b <> c
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