unit uTriangle; interface type TriangleKind = (Equilateral, Isosceles, Scalene); Triangle = class private class function AllSidesAreZero(aSide1, aSide2, aSide3: double): boolean; static; class function HasImpossibleSides(aSide1, aSide2, aSide3: double): boolean; static; class function ViolatesTriangleInequality(aSide1, aSide2, aSide3: double): boolean; static; class function UniqueSides(aSide1, aSide2, aSide3: double): integer; static; public class function Sides(aIsKind: TriangleKind; aSide1, aSide2, aSide3: double): boolean; static; end; implementation uses System.SysUtils; class function Triangle.AllSidesAreZero(aSide1, aSide2, aSide3: double): boolean; begin result := (aSide1 = 0) and (aSide2 = 0) and (aSide3 = 0); end; class function Triangle.HasImpossibleSides(aSide1, aSide2, aSide3: double): boolean; begin result := (aSide1 < 0) or (aSide2 < 0) or (aSide3 < 0); end; class function Triangle.ViolatesTriangleInequality(aSide1, aSide2, aSide3: double): boolean; begin result := (aSide1 + aSide2 <= aSide3) or (aSide1 + aSide3 <= aSide2) or (aSide2 + aSide3 <= aSide1); end; class function Triangle.UniqueSides(aSide1, aSide2, aSide3: double): integer; begin result := 1; if (aSide1 <> aSide2) and (aSide1 <> aSide3) then inc(result); if (aSide2 <> aSide1) and (aSide2 <> aSide3) then inc(result); if (aSide3 <> aSide2) and (aSide3 <> aSide1) then inc(result); if result > 3 then result := 3; end; class function Triangle.Sides(aIsKind: TriangleKind; aSide1, aSide2, aSide3: double): boolean; var luniqueSides: integer; begin result := false; if not (AllSidesAreZero(aSide1, aSide2, aSide3) or ViolatesTriangleInequality(aSide1, aSide2, aSide3) or HasImpossibleSides(aSide1, aSide2, aSide3)) then begin luniqueSides := UniqueSides(aSide1, aSide2, aSide3); result := ((luniqueSides = 1) and (aIsKind in [Equilateral, Isosceles])) or ((luniqueSides = 2) and (aIsKind = Isosceles)) or ((aIsKind = Scalene) and (luniqueSides = 3)); end; end; end.