Implemented 'compose' and 'andThen' for FragileFunction

Author: AlexanderSchultheiss

src/main/java/de/variantsync/evolution/util/functional/Functional.java

@@ -123,20 +123,4 @@ public static <Nullable, B, E extends Exception> Optional<B> mapFragile(final Nu
     public static <A, B, E extends Exception> Lazy<Optional<B>> mapFragileLazily(final A a, final FragileFunction<A, B, E> f, final Supplier<String> errorMessage) {
         return Lazy.of(() -> mapFragile(a, f, errorMessage));
     }
-
-    /**
-     * Chains two fragile functions. The chained function first applies f1 to a given input, and then applies f2 to the 
-     * output of f1 (i.e., given an input x the chained function corresponds to f2(f1(x)))
-     * @param f1 The inner function
-     * @param f2 The outer function
-     * @param <Input> The input type of the inner function
-     * @param <Intermediate> The input type of the outer function and the return type of the inner function
-     * @param <Output> The return type of the outer function
-     * @return A new FragileFunction f2(f1(x))
-     */
-    public static <Input, Intermediate, Output> FragileFunction<Input, Output, Exception> chainFragile(
-            final FragileFunction<Input, Intermediate, Exception> f1, 
-            final FragileFunction<Intermediate, Output, Exception> f2) {
-        return (Input input) -> f2.run(f1.run(input));
-    }
 }

src/main/java/de/variantsync/evolution/util/functional/interfaces/FragileFunction.java

@@ -3,4 +3,12 @@
 @FunctionalInterface
 public interface FragileFunction<A, B, E extends Exception> {
     B run(A a) throws E;
+    
+    default <Input, ExceptionBefore extends Exception> FragileFunction<Input, B, Exception> compose(final FragileFunction<Input, A, ExceptionBefore> before) {
+        return (Input input) -> this.run(before.run(input)); 
+    }
+    
+    default <Output, ExceptionAfter extends Exception> FragileFunction<A, Output, Exception> andThen(final FragileFunction<B, Output, ExceptionAfter> after) {
+        return (A input) -> after.run(this.run(input));
+    }
 }