# HG changeset patch
# User Christian Urban <christian.urban@kcl.ac.uk>
# Date 1605183531 0
# Node ID 7aab258bf72a1d27020ea9eb02fe7721ae65e037
# Parent  9eea6a801e10a5323362a7b7fc05d2bcd3b1fc6b
updated

diff -r 9eea6a801e10 -r 7aab258bf72a cws/cw03.pdf
Binary file cws/cw03.pdf has changed
diff -r 9eea6a801e10 -r 7aab258bf72a cws/cw03.tex
--- a/cws/cw03.tex	Sat Nov 07 00:07:28 2020 +0000
+++ b/cws/cw03.tex	Thu Nov 12 12:18:51 2020 +0000
@@ -55,7 +55,7 @@
 list, of \emph{tokens} generated by the tokenizer from the previous
 coursework. For this you might want to filter out whitespaces and
 comments. Your parser should be able to handle the WHILE programs in
-Figures~\ref{fib}, \ref{loop} and \ref{primes}.  In addition give the
+Figures~\ref{fib} -- \ref{collatz}.  In addition give the
 parse tree for the statement:
 
 \begin{lstlisting}[language=While,numbers=none]
diff -r 9eea6a801e10 -r 7aab258bf72a progs/parser-combinators/comb1.sc
--- a/progs/parser-combinators/comb1.sc	Sat Nov 07 00:07:28 2020 +0000
+++ b/progs/parser-combinators/comb1.sc	Thu Nov 12 12:18:51 2020 +0000
@@ -79,9 +79,13 @@
 // p"<_some_string_>" 
 
 implicit def parser_interpolation(sc: StringContext) = new {
-  def p(args: Any*) = StrParser(sc.s(args:_*))
+  def p(args: Any*) = TokParser(sc.s(args:_*))
 }
 
+p"while"  ==> StrParser[String,....]
+              TokParser[List[Token],....]
+
+for x := 3 to 10               
 
 // more convenient syntax for parser combinators
 implicit def ParserOps[I : IsSeq, T](p: Parser[I, T]) = new {
@@ -102,7 +106,7 @@
 
 
 // A parser for palindromes (just returns them as string)
-lazy val Pal : Parser[String, String] = {
+lazy val Pal : Parser[List[Token], String] = {
   (p"a" ~ Pal ~ p"a").map{ case ((x, y), z) => s"$x$y$z" } || 
   (p"b" ~ Pal ~ p"b").map{ case ((x, y), z) => s"$x$y$z" } || 
   p"a" || p"b" || p""
diff -r 9eea6a801e10 -r 7aab258bf72a progs/pow.scala
--- a/progs/pow.scala	Sat Nov 07 00:07:28 2020 +0000
+++ b/progs/pow.scala	Thu Nov 12 12:18:51 2020 +0000
@@ -6,6 +6,12 @@
   case n => concat(A, pow(A, n- 1))
 }
 
+val A = Set("a", "b", "c", "d", "e")
+val B = Set("a", "b", "c", "d", "")
+pow(A, 4).size
+pow(B, 4).size
+
+
 val A = Set("aa", "a")
 val B = Set("aaa", "aaaa")
 concat(A, B).size                     // -> 3