corrected / added midterm examples

src/MidTerm1/Ex2.sc

@@ -24,6 +24,23 @@ def predicates[T](list: List[T])(preds: List[T => Boolean]): List[T] = {
   })
 }
 
+val l1 = (1 to 10).toList
+val f1 = ((a: Int) => a % 2 == 0)
+val f2 = ((a: Int) => a > 5)
+predicates(l1)(List(f1, f2))  // List(6, 8, 10)
+
+val l2 = ("Hello Scala Echo").toList
+val f4 = ((a: Char) => a == 'a' || a == 'e' || a == 'o')
+val f3 = ((a: Char) => !a.isUpper)
+predicates(l2)(List(f3, f4))  // List('e', 'o', 'a', 'a', 'o')
+
+/*
+// Better solution
+def predicates[T](list: List[T])(preds: List[T => Boolean]): List[T] = {
+  preds.foldLeft(list)((acc, fun) => acc.filter(fun))
+}
+*/
+
 def fixedPoint(f: Int => Int): Int => Int = {
   @tailrec
   def func(x: Int): Int = {
@@ -34,4 +51,5 @@ def fixedPoint(f: Int => Int): Int => Int = {
   func
 }
 
-fixedPoint(x => x / 2 + 5)(40)
+fixedPoint(x => if (x % 10 == 0) x else x + 1)(35)  // 40
+fixedPoint(x => x / 2 + 5)(20)  // 10

src/MidTerm1/Ex3.sc

@@ -16,7 +16,7 @@ abstract class Text {
   def tail: Text = {
     this match {
       case Chars(cs) => Chars(cs.tail)
-      case Concat(t1, t2) => if (t2.isEmpty) t1.tail else Concat(t1, t2.tail)
+      case Concat(t1, t2) => if (t1.isEmpty) t2.tail else Concat(t1.tail, t2)
     }
   }
   def map(f: Char => Char): Text = {