Merge pull request #55 from reganlaurell/area

Implement Area Calculations

Author: vbrazo

src/main/kotlin/math/Area.kt

@@ -0,0 +1,53 @@
+package math
+
+import java.lang.IllegalArgumentException
+import kotlin.math.pow
+
+/**
+ * Calculate the area of a rectangle
+ *
+ * @param length length of rectangle
+ * @param width width of rectangle
+ * @return area of given rectangle
+ */
+fun areaOfARectangle(length: Double, width: Double) =  when {
+    length > 0 && width > 0 -> length * width
+    else -> throw IllegalArgumentException("Length and Width must be positive")
+}
+
+/**
+ * Calculate the area of a square
+ *
+ * @param sideLength side length of square
+ * @return area of given square
+ */
+fun areaOfASquare(sideLength: Double) =
+    when {
+        sideLength > 0 -> sideLength * sideLength
+        else -> throw IllegalArgumentException("Side Length must be positive")
+    }
+
+/**
+ * Calculate the area of a triangle
+ *
+ * @param base base of triangle
+ * @param height height of triangle
+ * @return area of given triangle
+ */
+fun areaOfATriangle(base: Double, height: Double) =
+    when {
+        base > 0 && height > 0 -> base * height / 2
+        else -> throw IllegalArgumentException("Base and Height must be positive")
+    }
+
+/**
+ * Calculate the area of a circle
+ *
+ * @param radius radius of circle
+ * @return area of given circle
+ */
+fun areaOfACircle(radius: Double) =
+    when {
+        radius > 0 -> Math.PI * radius.pow(2.0)
+        else -> throw IllegalArgumentException("Radius must be positive")
+    }

src/test/kotlin/math/AreaTest.kt

@@ -0,0 +1,34 @@
+package math
+
+import org.junit.Test
+import java.lang.IllegalArgumentException
+
+class AreaTest {
+    @Test
+    fun testAreaOfARectangle() = assert(areaOfARectangle(10.0, 5.0) == 50.0)
+
+    @Test
+    fun testAreaOfASquare() = assert(areaOfASquare(5.0) == 25.0)
+
+    @Test
+    fun testAreaOfACircle() = assert(areaOfACircle(1.0) == Math.PI)
+
+    @Test
+    fun testAreaOfATriangle() = assert(areaOfATriangle(5.0, 10.0) == 25.0)
+
+    @Test(expected = IllegalArgumentException::class)
+    fun testAreaWithNegatives() {
+        areaOfARectangle(-1.0, 0.0)
+        areaOfASquare(-1.0)
+        areaOfACircle(-1.0)
+        areaOfATriangle(-1.0, 1.0)
+    }
+
+    @Test(expected = IllegalArgumentException::class)
+    fun testAreaWithZeros() {
+        areaOfARectangle(0.0, 0.0)
+        areaOfASquare(0.0)
+        areaOfACircle(0.0)
+        areaOfATriangle(0.0, 1.0)
+    }
+}