--- a/marking/mark02 Tue Jan 24 12:57:40 2017 +0000
+++ b/marking/mark02 Wed Jan 25 01:25:04 2017 +0000
@@ -12,7 +12,7 @@
echo "" >> $out
function scala_vars {
- (egrep '\bvar\b|\breturn\b|ListBuffer|mutable' "$1" 2> /dev/null 1> /dev/null)
+ (egrep 'var|return|ListBuffer|mutable' "$1" 2> /dev/null 1> /dev/null)
}
@@ -189,6 +189,38 @@
fi
+# knights3: var, comments test
+#
+#echo "knight3.scala does not contain vars, returns etc?" | tee -a $out
+
+#if (scala_vars knight3.scala)
+#then
+# echo " --> fail" | tee -a $out
+# tsts0=$(( 1 ))
+#else
+# echo " --> success" | tee -a $out
+# tsts0=$(( 0 ))
+#fi
+
+
+# compilation test
+#if [ $tsts0 -eq 0 ]
+#then
+# echo "knight3.scala runs?" | tee -a $out
+#
+# if (scala_compile knight3.scala.bak)
+# then
+# echo " --> success" | tee -a $out
+# tsts1=$(( 0 ))
+# else
+# echo " --> scala did not run knight3.scala" | tee -a $out
+# tsts1=$(( 1 ))
+# fi
+#else
+# tsts1=$(( 1 ))
+#fi
+
+
## final marks
-echo "Overall mark for CW 7, Part 1 " | tee -a $out
+echo "Overall mark for CW 2, Part 1 " | tee -a $out
echo "$marks" | tee -a $out
--- a/marking/mark02b Tue Jan 24 12:57:40 2017 +0000
+++ b/marking/mark02b Wed Jan 25 01:25:04 2017 +0000
@@ -26,7 +26,7 @@
# functional tests
function scala_assert {
- (scala -i "$1" "$2" -e "" 2> /dev/null 1> /dev/null)
+ (scala -i "$1" "$2" -e "") # 2> /dev/null 1> /dev/null)
}
@@ -65,12 +65,11 @@
tsts1=$(( 1 ))
fi
-
if [ $tsts1 -eq 0 ]
then
- echo " ordered_moves(8, List((3,4), (3,2)), (1,3)) == (0,1), (0,5), (2,1), (2,5)" | tee -a $out
- echo " ordered_moves(8, List((4,0)), (0,0)) == (2,1), (1,2)" | tee -a $out
- echo " ordered_moves(8, List((0,4)), (0,0)) == (1,2), (2,1)" | tee -a $out
+ echo " ordered_moves(8, List((3,4), (3,2)), (1, 3)) == List((0,1), (0,5), (2,1), (2,5))" | tee -a $out
+ echo " ordered_moves(8, List((4,0)), (0,0)) == List((2,1), (1,2))" | tee -a $out
+ echo " ordered_moves(8, List((0,4)), (0,0)) == List((1,2), (2,1))" | tee -a $out
if (scala_assert "knight3.scala.bak" "../../../marking/knight3a_test.scala")
then
@@ -83,7 +82,7 @@
if [ $tsts1 -eq 0 ]
then
- echo " first_closed_tour_heuristic(6, List((3, 3))) is ok?" | tee -a $out
+ echo " first_closed_tour_heuristic(6, List((3, 3))) found and ok?" | tee -a $out
if (scala_assert "knight3.scala.bak" "../../../marking/knight3b_test.scala")
then
@@ -94,6 +93,20 @@
fi
fi
+if [ $tsts1 -eq 0 ]
+then
+ echo " first_tour_heuristic(8, List((0,0))) found and ok?" | tee -a $out
+ echo " first_tour_heuristic(50, List((0,0))) found and ok?" | tee -a $out
+
+ if (scala_assert "knight3.scala.bak" "../../../marking/knight3c_test.scala")
+ then
+ echo " --> success" | tee -a $out
+ marks=$(( marks + 1 ))
+ else
+ echo " --> test failed" | tee -a $out
+ fi
+fi
+
## final marks
echo "Overall mark for CW 7, Part 2" | tee -a $out
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/progs/re2_sol.scala Wed Jan 25 01:25:04 2017 +0000
@@ -0,0 +1,215 @@
+// Part 1 about Regular Expression Matching
+//==========================================
+
+abstract class Rexp
+case object ZERO extends Rexp
+case object ONE extends Rexp
+case class CHAR(c: Char) extends Rexp
+case class ALT(r1: Rexp, r2: Rexp) extends Rexp
+case class SEQ(r1: Rexp, r2: Rexp) extends Rexp
+case class STAR(r: Rexp) extends Rexp
+
+// some convenience for typing in regular expressions
+
+import scala.language.implicitConversions
+import scala.language.reflectiveCalls
+
+def charlist2rexp(s: List[Char]): Rexp = s match {
+ case Nil => ONE
+ case c::Nil => CHAR(c)
+ case c::s => SEQ(CHAR(c), charlist2rexp(s))
+}
+implicit def string2rexp(s: String): Rexp = charlist2rexp(s.toList)
+
+implicit def RexpOps (r: Rexp) = new {
+ def | (s: Rexp) = ALT(r, s)
+ def % = STAR(r)
+ def ~ (s: Rexp) = SEQ(r, s)
+}
+
+implicit def stringOps (s: String) = new {
+ def | (r: Rexp) = ALT(s, r)
+ def | (r: String) = ALT(s, r)
+ def % = STAR(s)
+ def ~ (r: Rexp) = SEQ(s, r)
+ def ~ (r: String) = SEQ(s, r)
+}
+
+// (1a) Complete the function nullable according to
+// the definition given in the coursework; this
+// function checks whether a regular expression
+// can match the empty string
+
+def nullable (r: Rexp) : Boolean = r match {
+ case ZERO => false
+ case ONE => true
+ case CHAR(_) => false
+ case ALT(r1, r2) => nullable(r1) || nullable(r2)
+ case SEQ(r1, r2) => nullable(r1) && nullable(r2)
+ case STAR(_) => true
+}
+
+// (1b) Complete the function der according to
+// the definition given in the coursework; this
+// function calculates the derivative of a
+// regular expression w.r.t. a character
+
+def der (c: Char, r: Rexp) : Rexp = r match {
+ case ZERO => ZERO
+ case ONE => ZERO
+ case CHAR(d) => if (c == d) ONE else ZERO
+ case ALT(r1, r2) => ALT(der(c, r1), der(c, r2))
+ case SEQ(r1, r2) =>
+ if (nullable(r1)) ALT(SEQ(der(c, r1), r2), der(c, r2))
+ else SEQ(der(c, r1), r2)
+ case STAR(r1) => SEQ(der(c, r1), STAR(r1))
+}
+
+// (1c) Complete the function der according to
+// the specification given in the coursework; this
+// function simplifies a regular expression;
+// however it does not simplify inside STAR-regular
+// expressions
+
+def simp(r: Rexp) : Rexp = r match {
+ case ALT(r1, r2) => (simp(r1), simp(r2)) match {
+ case (ZERO, r2s) => r2s
+ case (r1s, ZERO) => r1s
+ case (r1s, r2s) => if (r1s == r2s) r1s else ALT (r1s, r2s)
+ }
+ case SEQ(r1, r2) => (simp(r1), simp(r2)) match {
+ case (ZERO, _) => ZERO
+ case (_, ZERO) => ZERO
+ case (ONE, r2s) => r2s
+ case (r1s, ONE) => r1s
+ case (r1s, r2s) => SEQ(r1s, r2s)
+ }
+ case r => r
+}
+
+// (1d) Complete the two functions below; the first
+// calculates the derivative w.r.t. a string; the second
+// is the regular expression matcher taking a regular
+// expression and a string and checks whether the
+// string matches the regular expression
+
+def ders (s: List[Char], r: Rexp) : Rexp = s match {
+ case Nil => r
+ case c::s => ders(s, simp(der(c, r)))
+}
+
+// main matcher function
+def matcher(r: Rexp, s: String): Boolean = nullable(ders(s.toList, r))
+
+
+// (1e) Complete the function below: it searches (from the left to
+// right) in string s1 all the non-empty substrings that match the
+// regular expression -- these substrings are assumed to be
+// the longest substrings matched by the regular expression and
+// assumed to be non-overlapping. All these substrings in s1 are replaced
+// by s2.
+
+
+
+def splits(s: String): List[(String, String)] =
+ (for (i <- (1 to s.length).toList) yield s.splitAt(i)).reverse
+
+splits("abcde")
+splits("")
+
+def first(r: Rexp, lst: List[(String, String)]): Option[String] = lst match {
+ case Nil => None
+ case (s1, s2)::xs => if (matcher(r, s1)) Some(s2) else first(r, xs)
+}
+
+"abcd".head
+
+def replace(r: Rexp, s1: String, s2: String): String = first(r, splits(s1)) match {
+ case None if (s1 == "") => ""
+ case None => s1.head.toString ++ replace(r, s1.tail, s2)
+ case Some(s) => s2 ++ replace(r, s, s2)
+}
+
+val s1 = "aabbbaaaaaaabaaaaabbaaaabb"
+val r: Rexp = "aa".% | "bb"
+splits(s1)
+first(r, splits(s1))
+
+replace(r, s1, "c")
+
+splits("bb")
+first(r, splits("bb"))
+replace(r, "abb", "c")
+
+
+// PART 2
+//========
+
+
+// (2a)
+
+import scala.annotation.tailrec
+
+@tailrec
+def iterT[A](n: Int, f: A => A, x: A): A =
+ if (n == 0) x else iterT(n - 1, f, f(x))
+
+
+//non-tail recursive iter
+
+def iter[A](n: Int, f: A => A, x: A): A =
+ if (n == 0) x else f(iter(n - 1,f, x))
+
+
+iter(200000, (x: Int) => x + 1, 0)
+iterT(200000, (x: Int) => x + 1, 0)
+iterT(100, (x: Int) => x * 2, 2)
+iterT(100, (x: BigInt) => x * 2, BigInt(2))
+iterT(10, (x: String) => x ++ "a", "a")
+
+// (2b)
+
+def size(r: Rexp): Int = r match {
+ case ZERO => 1
+ case ONE => 1
+ case CHAR(_) => 1
+ case ALT(r1, r2) => 1 + size(r1) + size (r2)
+ case SEQ(r1, r2) => 1 + size(r1) + size (r2)
+ case STAR(r1) => 1 + size(r1)
+}
+
+
+val EVIL = SEQ(STAR(STAR(CHAR('a'))), CHAR('b'))
+size(iterT(20, (r: Rexp) => der('a', r), EVIL)) // should produce 7340068
+size(iterT(20, (r: Rexp) => simp(der('a', r)), EVIL)) // should produce 8
+
+
+// (2c)
+
+@tailrec
+def fixpT[A](f: A => A, x: A): A = {
+ val fx = f(x)
+ if (fx == x) x else fixpT(f, fx)
+}
+
+fixpT((x:Int) => if (200000 < x) x else x + 1, 0)
+
+def ctest(n: Long): Long =
+ if (n == 1) 1 else
+ if (n % 2 == 0) n / 2 else 3 * n + 1
+
+fixpT(ctest, 97L)
+fixpT(ctest, 871L)
+fixpT(ctest, 77031L)
+fixpT(ctest, 837799L)
+
+def foo(s: String): String = {
+ if (matcher("a", s)) "a" else
+ if (matcher("aa" ~ STAR("aa"), s)) s.take(s.length / 2)
+ else "a" ++ s * 3
+}
+
+fixpT(foo, "a" * 97)
+fixpT(foo, "a" * 871)
+
+