1 files changed, 68 insertions, 0 deletions
diff --git a/docs/examples/parsing/lambda/TestParser.scala b/docs/examples/parsing/lambda/TestParser.scala
new file mode 100755
index 0000000000..92d370c29b
--- /dev/null
+++ b/docs/examples/parsing/lambda/TestParser.scala
@@ -0,0 +1,68 @@
+package examples.parsing.lambda
+
+import scala.util.parsing.input.Reader
+import scala.util.parsing.combinator.lexical.StdLexical
+import scala.util.parsing.combinator.syntactical.StdTokenParsers
+import scala.util.parsing.combinator.ImplicitConversions
+
+/**
+ * Parser for an untyped lambda calculus
+ *
+ * @author Miles Sabin (adapted slightly by Adriaan Moors)
+ */
+trait TestParser extends StdTokenParsers  with ImplicitConversions with TestSyntax
+{
+  type Tokens = StdLexical
+  val lexical = new StdLexical
+  lexical.reserved ++= List("unit", "let", "in", "if", "then", "else")
+  lexical.delimiters ++= List("=>", "->", "==", "(", ")", "=", "\\", "+", "-", "*", "/")
+
+
+	def name : Parser[Name] = ident ^^ Name
+
+  // meaning of the argumens to the closure during subsequent iterations
+  // (...(expr2 op1 expr1) ... op1 expr1)
+  //      ^a^^^ ^o^ ^b^^^
+  //      ^^^^^^^a^^^^^^^      ^o^ ^^b^^
+  def expr1 : Parser[Term] =
+    chainl1(expr2, expr1, op1 ^^ {o => (a: Term, b: Term) => App(App(o, a), b)})
+
+  def expr2 : Parser[Term] =
+   chainl1(expr3, expr2, op2 ^^ {o => (a: Term, b: Term) => App(App(o, a), b)})
+
+  def expr3 : Parser[Term] =
+   chainl1(expr4, expr3, op3 ^^ {o => (a: Term, b: Term) => App(App(o, a), b)})
+
+  def expr4 : Parser[Term] =
+  ( "\\" ~ lambdas
+  | "let" ~ name ~ "=" ~ expr1 ~ "in" ~ expr1 ^^ flatten3(Let)
+  | "if" ~ expr1 ~ "then" ~ expr1 ~ "else" ~ expr1 ^^ flatten3(If)
+  | chainl1(aexpr, success(App(_: Term, _: Term)))
+  )
+
+  def lambdas : Parser[Term] =
+    name ~ ("->" ~ expr1 | lambdas) ^^ flatten2(Lam)
+
+  def aexpr : Parser[Term] =
+  ( numericLit ^^ (_.toInt) ^^ Lit
+  | name ^^ Ref
+  | "unit" ^^ Unit
+  | "(" ~ expr1 ~ ")"
+  )
+
+  def op1 : Parser[Term] =
+    "=="  ^^ Ref(Name("=="))
+
+  def op2 : Parser[Term] =
+  ( "+" ^^ Ref(Name("+"))
+  | "-" ^^ Ref(Name("-"))
+  )
+
+  def op3 : Parser[Term] =
+  ( "*" ^^ Ref(Name("*"))
+  | "/" ^^ Ref(Name("/"))
+  )
+
+  def parse(r: Reader[char]) : ParseResult[Term] =
+    phrase(expr1)(new lexical.Scanner(r))
+}