1 files changed, 160 insertions, 0 deletions
diff --git a/examples/go/rpn.rl b/examples/go/rpn.rl
new file mode 100644
index 00000000..1716ab3b
--- /dev/null
+++ b/examples/go/rpn.rl
@@ -0,0 +1,160 @@
+// -*-go-*-
+//
+// Reverse Polish Notation Calculator
+// Copyright (c) 2010 J.A. Roberts Tunney
+// MIT License
+//
+// To compile:
+//
+//   ragel -Z -G2 -o rpn.go rpn.rl
+//   6g -o rpn.6 rpn.go
+//   6l -o rpn rpn.6
+//   ./rpn
+//
+// To show a diagram of your state machine:
+//
+//   ragel -V -G2 -p -o rpn.dot rpn.rl
+//   dot -Tpng -o rpn.png rpn.dot
+//   chrome rpn.png
+//
+
+package main
+
+import (
+	"os"
+	"fmt"
+	"strconv"
+)
+
+type stack struct {
+	items []int
+	count int
+}
+
+func (s *stack) pop() int {
+	s.count--
+	v := s.items[s.count]
+	return v
+}
+
+func (s *stack) push(v int) {
+	s.items[s.count] = v
+	s.count++
+}
+
+func abs(v int) int {
+	if v < 0 {
+		v = -v
+	}
+	return v
+}
+
+%% machine rpn;
+%% write data;
+
+func rpn(data string) (res int, err os.Error) {
+	// p, pe, eof := 0, len(data), len(data)
+	cs, p, pe := 0, 0, len(data)
+	mark := 0
+	st := &stack{items: make([]int, 128), count: 0}
+
+	%%{
+		action mark { mark = p }
+		action push { x, _ := strconv.Atoi(data[mark:p]); st.push(x) }
+		action add  { y, x := st.pop(), st.pop(); st.push(x + y) }
+		action sub  { y, x := st.pop(), st.pop(); st.push(x - y) }
+		action mul  { y, x := st.pop(), st.pop(); st.push(x * y) }
+		action div  { y, x := st.pop(), st.pop(); st.push(x / y) }
+		action abs  { st.push(abs(st.pop())) }
+		action abba { st.push(666) }
+
+		stuff  = digit+ >mark %push
+		       | '+' @add
+		       | '-' @sub
+		       | '*' @mul
+		       | '/' @div
+		       | 'abs' %abs
+		       | 'add' %add
+		       | 'abba' %abba
+		       ;
+
+		main := ( space | stuff space )* ;
+
+		write init;
+		write exec;
+	}%%
+
+	if cs < rpn_first_final {
+		if p == pe {
+			return 0, os.ErrorString("unexpected eof")
+		} else {
+			return 0, os.ErrorString(fmt.Sprintf("error at position %d", p))
+		}
+	}
+
+	if st.count == 0 {
+		return 0, os.ErrorString("rpn stack empty on result")
+	}
+
+	return st.pop(), nil
+}
+
+//////////////////////////////////////////////////////////////////////
+
+type rpnTest struct {
+	s string
+	v int
+}
+
+var rpnTests = []rpnTest{
+	rpnTest{"666\n", 666},
+	rpnTest{"666 111\n", 111},
+	rpnTest{"4 3 add\n", 7},
+	rpnTest{"4 3 +\n", 7},
+	rpnTest{"4 3 -\n", 1},
+	rpnTest{"4 3 *\n", 12},
+	rpnTest{"6 2 /\n", 3},
+	rpnTest{"0 3 -\n", -3},
+	rpnTest{"0 3 - abs\n", 3},
+	rpnTest{" 2  2 + 3 - \n", 1},
+	rpnTest{"10 7 3 2 * - +\n", 11},
+	rpnTest{"abba abba add\n", 1332},
+}
+
+type rpnFailTest struct {
+	s string
+	e string
+}
+
+var rpnFailTests = []rpnFailTest{
+	rpnFailTest{"\n", "rpn stack empty on result"},
+}
+
+func main() {
+	rc := 0
+
+	for _, test := range rpnTests {
+		res, err := rpn(test.s)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "FAIL rpn(%#v) %s\n", test.s, err)
+			rc = 1
+		} else if res != test.v {
+			fmt.Fprintf(os.Stderr, "FAIL rpn(%#v) -> %#v != %#v\n",
+				test.s, res, test.v)
+			rc = 1
+		}
+	}
+
+	for _, test := range rpnFailTests {
+		res, err := rpn(test.s)
+		if err == nil {
+			fmt.Fprintf(os.Stderr, "FAIL rpn(%#v) -> %#v should fail: %#v\n",
+				test.s, res, test.e)
+		} else if err.String() != test.e {
+			fmt.Fprintf(os.Stderr, "FAIL rpn(%#v) %#v should be %#v\n",
+				test.s, err.String(), test.e)
+		}
+	}
+
+	os.Exit(rc)
+}