Impl prototype scanner.

Author: harukasan

.gitignore

@@ -0,0 +1 @@
+*_string.go

README.md

@@ -1,2 +1,3 @@
-# ringo
-Ruby in Go
+# Ringo
+
+Ringo is experimental project to implement ruby interpreter in Golang.

debug/debug.go

@@ -0,0 +1,55 @@
+/*
+Package debug implements utility functions to output debug message.
+
+The debug messages can enable by Enable variable, for instance:
+
+	debug.Enable = true
+
+	debug.Print("debug message")
+	// Output:
+	// debug message
+
+*/
+package debug
+
+import (
+	"fmt"
+	"os"
+	"path"
+	"runtime"
+)
+
+// Enable specifies whether the debug prints messages into the Output.
+var Enable = false
+
+// Output specifies the destination to print out messages.
+var Output = os.Stderr
+
+func output(s string) {
+	_, file, line, _ := runtime.Caller(2)
+	fmt.Fprintf(Output, "%s:%d> %s", path.Base(file), line, s)
+	if s[len(s)-1] != '\n' {
+		Output.Write([]byte{'\n'})
+	}
+}
+
+// Print prints debug message in manner of fmt.Sprint.
+func Print(v ...interface{}) {
+	if Enable {
+		output(fmt.Sprint(v...))
+	}
+}
+
+// Println prints debug message in manner of fmt.Sprintln.
+func Println(v ...interface{}) {
+	if Enable {
+		output(fmt.Sprintln(v...))
+	}
+}
+
+// Printf prints debug message in manner of fmt.Sprintf.
+func Printf(format string, v ...interface{}) {
+	if Enable {
+		output(fmt.Sprintf(format, v...))
+	}
+}

debug/debug_test.go

@@ -0,0 +1,38 @@
+package debug_test
+
+import (
+	"os"
+
+	"github.com/harukasan/ringo/debug"
+)
+
+func ExamplePrint() {
+	debug.Enable = true
+	// set output to stdout for testing
+	debug.Output = os.Stdout
+	//
+	//
+	debug.Print("Hello, world!") // line: 15
+	// Output:
+	// debug_test.go:15> Hello, world!
+}
+
+func ExamplePrintln() {
+	debug.Enable = true
+	// set output to stdout for testing
+	debug.Output = os.Stdout
+
+	debug.Println("Hello, world!") // line: 25
+	// Output:
+	// debug_test.go:25> Hello, world!
+}
+
+func ExamplePrintf() {
+	debug.Enable = true
+	// set output to stdout for testing
+	debug.Output = os.Stdout
+
+	debug.Printf("a: %v", true) // line: 35
+	// Output:
+	// debug_test.go:35> a: true
+}

scanner/error.go

@@ -0,0 +1,13 @@
+package scanner
+
+import "fmt"
+
+// ScanError holds an error which is caused by scanner.
+type ScanError struct {
+	Pos int
+	Err error
+}
+
+func (e *ScanError) Error() string {
+	return fmt.Sprintf("%v at pos=%d", e.Err, e.Pos)
+}