diff --git a/src/main/java/_7/_1/Function.java b/src/main/java/_7/_1/Function.java
new file mode 100644
index 0000000..950536d
--- /dev/null
+++ b/src/main/java/_7/_1/Function.java
@@ -0,0 +1,6 @@
+package _7._1;
+
+public interface Function<T extends Number, G extends Number> {
+    G calculate(T x);
+}
+
diff --git a/src/main/java/_7/_1/LambdaTest.java b/src/main/java/_7/_1/LambdaTest.java
new file mode 100644
index 0000000..67271da
--- /dev/null
+++ b/src/main/java/_7/_1/LambdaTest.java
@@ -0,0 +1,32 @@
+package _7._1;
+
+public class LambdaTest {
+
+    public static void main(String[] args) {
+        Function<Double,Double> id = (x) -> x;
+
+        Function<Double,Double> inverse = (x) -> x*-1;
+
+        Function<Double,Double> timesTen = (x) -> x*10;
+
+        Function<Double,Double> divideByPi = (x) -> x/Math.PI;
+
+        Function<Double,Long> round = Math::round;
+
+
+        @SuppressWarnings("unchecked")
+        Function<Double, Double> chain = makeChain(new Function[] {inverse, id, timesTen, divideByPi});
+
+        System.out.println(round.calculate((chain.calculate(5.5))));
+    }
+
+    private static Function<Double, Double> makeChain(final Function<Double, Double>[] functions) {
+        return  (x) -> {
+            for (Function<Double, Double> i : functions) {
+                x = i.calculate(x);
+            }
+            return x;
+        };
+    }
+
+}