updated examples to new combinator library

2 files changed, 90 insertions, 0 deletions

diff --git a/docs/examples/parsing/ArithmeticParser.scala b/docs/examples/parsing/ArithmeticParser.scala
new file mode 100644
index 0000000000..2aac4b6f6c
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+++ b/docs/examples/parsing/ArithmeticParser.scala
@@ -0,0 +1,57 @@
+/*                     __                                               *\
+**     ________ ___   / /  ___     Scala API                            **
+**    / __/ __// _ | / /  / _ |    (c) 2006-2007, LAMP/EPFL             **
+**  __\ \/ /__/ __ |/ /__/ __ |                                         **
+** /____/\___/_/ |_/____/_/ | |                                         **
+**                          |/                                          **
+\*                                                                      */
+
+package examples.parsing
+
+import scala.util.parsing.combinator.lexical.StdLexical
+import scala.util.parsing.combinator.syntactical.StdTokenParsers
+
+/** Parse and evaluate a numeric expression as a sequence of terms, separated by + or -
+ *   a term is a sequence of factors, separated by * or /
+ *   a factor is a parenthesized expression or a number
+ *
+ * @author Adriaan Moors
+ */
+object arithmeticParser extends StdTokenParsers {
+  type Tokens = StdLexical ; val lexical = new StdLexical
+  lexical.delimiters ++= List("(", ")", "+", "-", "*", "/")
+
+  lazy val expr =   term*("+" ^^ {(x: int, y: int) => x + y} | "-" ^^ {(x: int, y: int) => x - y})
+  lazy val term = factor*("*" ^^ {(x: int, y: int) => x * y} | "/" ^^ {(x: int, y: int) => x / y})
+  lazy val factor: Parser[int] = "(" ~ expr ~ ")" | numericLit ^^ (_.toInt)
+
+  def main(args: Array[String]) {
+    println(
+      if (args.length == 1) {
+        expr(new lexical.Scanner(args(0)))
+      }
+      else
+        "usage: scala examples.parsing.arithmeticParser <expr-string>"
+    )
+  }
+}
+
+
+object arithmeticParserDesugared extends StdTokenParsers {
+  type Tokens = StdLexical ; val lexical = new StdLexical
+  lexical.delimiters ++= List("(", ")", "+", "-", "*", "/")
+
+  lazy val expr = chainl1(term, (keyword("+").^^{(x: int, y: int) => x + y}).|(keyword("-").^^{(x: int, y: int) => x - y}))
+  lazy val term = chainl1(factor, (keyword("*").^^{(x: int, y: int) => x * y}).|(keyword("/").^^{(x: int, y: int) => x / y}))
+  lazy val factor: Parser[int] = keyword("(").~(expr.~(keyword(")"))).|(numericLit.^^(x => x.toInt))
+
+  def main(args: Array[String]) {
+    println(
+      if (args.length == 1) {
+        expr(new lexical.Scanner(args(0)))
+      }
+      else
+        "usage: scala examples.parsing.arithmeticParser <expr-string>"
+    )
+  }
+}
\ No newline at end of file
diff --git a/docs/examples/parsing/ListParser.scala b/docs/examples/parsing/ListParser.scala
new file mode 100644
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+++ b/docs/examples/parsing/ListParser.scala
@@ -0,0 +1,33 @@
+package examples.parsing
+
+import scala.util.parsing.combinator.{Parsers, ImplicitConversions, ~, mkTilde}
+import scala.util.parsing.input.CharArrayReader
+
+object listParser {
+  abstract class Tree
+  case class Id(s: String)          extends Tree
+  case class Num(n: Int)            extends Tree
+  case class Lst(elems: List[Tree]) extends Tree
+
+  import Character.{isLetter, isLetterOrDigit, isDigit}
+  def mkString(cs: List[Any]) = cs.mkString("")
+
+  class ListParsers extends Parsers {
+    type Elem = Char
+
+    lazy val ident = rep1(elem("letter", isLetter), elem("letter or digit", isLetterOrDigit)) ^^ {cs => Id(mkString(cs))}
+    lazy val number = chainl1(elem("digit", isDigit) ^^ (_ - '0'), success ^^ {(accum: Int, d: Int) => accum * 10 + d}) ^^ Num
+    lazy val list = '(' ~ repsep(expr, ',') ~ ')' ^^ Lst
+    lazy val expr: Parser[Tree] = list | ident | number
+  }
+
+  def main(args: Array[String]) {
+    println(
+      if (args.length == 1) {
+        (new ListParsers).expr(new CharArrayReader(args(0).toCharArray()))
+      }
+      else
+        "usage: scala examples.parsing.listParser <list-string>"
+    )
+  }
+}