Scala: all steps 0-9 but no metadata.

1 files changed, 88 insertions, 0 deletions

diff --git a/scala/reader.scala b/scala/reader.scala
new file mode 100644
index 0000000..fc16f28
--- /dev/null
+++ b/scala/reader.scala
@@ -0,0 +1,88 @@
+import scala.util.matching.Regex
+
+object reader {
+
+  class Reader (tokens: Array[String]) {
+    var data = tokens
+    var position: Int = 0
+    def peek(): String = {
+      if (position >= data.length) return(null)
+      data(position)
+    }
+    def next(): String = {
+      if (position >= data.length) return(null)
+      position = position + 1
+      data(position-1)
+    }
+  }
+
+  def tokenize(str: String): Array[String] = {
+    val re = """[\s,]*(~@|[\[\]{}()'`~^@]|"(?:\\.|[^\\"])*"|;.*|[^\s\[\]{}('"`,;)]*)""".r
+    re.findAllMatchIn(str).map{ _.group(1) }
+                          .filter{ s => s != "" && s(0) != ';' }
+                          .toArray
+  }
+
+  def parse_str(s: String): String = {
+    s.replace("\\\"", "\"").replace("\\n", "\n")
+  }
+
+  def read_atom(rdr: Reader): Any = {
+    val token = rdr.next()
+    val re_int = """^(-?[0-9]+)$""".r
+    val re_flt = """^(-?[0-9][0-9.]*)$""".r
+    val re_str =  """^"(.*)"$""".r
+    val re_key = """^:(.*)$""".r
+    return token match {
+      case re_int(i) => i.toInt       // integer
+      case re_flt(f) => f.toDouble    // float
+      case re_str(s) => parse_str(s)  // string
+      case re_key(k) => "\u029e" + k  // keyword
+      case "nil"     => null
+      case "true"    => true
+      case "false"   => false
+      case _         => Symbol(token) // symbol
+    }
+  }
+
+  def read_list(rdr: Reader,
+                start: String = "(", end: String = ")"): List[Any] = {
+    var ast: List[Any] = List()
+    var token = rdr.next()
+    if (token != start) throw new Exception("expected '" + start + "', got EOF")
+    while ({token = rdr.peek(); token != end}) {
+      if (token == null) throw new Exception("expected '" + end + "', got EOF")
+      ast = ast :+ read_form(rdr)
+    }
+    rdr.next()
+    ast
+  }
+
+  def read_form(rdr: Reader): Any = {
+    return rdr.peek() match {
+      case "'"  => { rdr.next; List(Symbol("quote"), read_form(rdr)) }
+      case "`"  => { rdr.next; List(Symbol("quasiquote"), read_form(rdr)) }
+      case "~"  => { rdr.next; List(Symbol("unquote"), read_form(rdr)) }
+      case "~@" => { rdr.next; List(Symbol("splice-unquote"), read_form(rdr)) }
+      case "^"  => { rdr.next; val meta = read_form(rdr);
+                     List(Symbol("with-meta"), read_form(rdr), meta) }
+      case "@"  => { rdr.next; List(Symbol("deref"), read_form(rdr)) }
+
+      case "("  => read_list(rdr)
+      case ")"  => throw new Exception("unexpected ')')")
+      case "["  => read_list(rdr, "[", "]").toArray
+      case "]"  => throw new Exception("unexpected ']')")
+      case "{"  => types._hash_map(read_list(rdr, "{", "}"))
+      case "}"  => throw new Exception("unexpected '}')")
+      case _    => read_atom(rdr)
+    }
+  }
+
+  def read_str(str: String): Any = {
+    val tokens = tokenize(str)
+    if (tokens.length == 0) return null
+    return read_form(new Reader(tokens))
+  }
+}
+
+// vim: ts=2:sw=2