new helpers (needed for drivel)

goutil.go

@@ -1,12 +1,24 @@
 package goutil
 
 import (
+	"bufio"
+	"errors"
+	"fmt"
 	"io/ioutil"
+	"os"
 	"path"
 	"path/filepath"
 	"strings"
 )
 
+func DecorateError(s string, err error) error {
+	if err != nil {
+		return errors.New(s + ": " + err.Error())
+	} else {
+		return nil
+	}
+}
+
 func WriteFile(filename string, data string) error {
 	return ioutil.WriteFile(filename, []byte(data), 0644)
 }
@@ -36,3 +48,53 @@ func ListFilesExt(dir string, ext string) []string {
 	}
 	return list
 }
+
+func PathExists(path string) bool {
+	if _, err := os.Stat(path); os.IsNotExist(err) {
+		return false
+	} else {
+		return true
+	}
+}
+
+func AskFor(question string) (string, error) {
+	fmt.Print(question + ": ")
+	reader := bufio.NewReader(os.Stdin)
+	s, err := reader.ReadString('\n')
+	if err == nil {
+		return strings.TrimSpace(s), nil
+	} else {
+		return "", err
+	}
+}
+
+func IntMin(x, y int) int {
+	if x < y {
+		return x
+	} else {
+		return y
+	}
+}
+
+func IntMax(x, y int) int {
+	if x > y {
+		return x
+	} else {
+		return y
+	}
+}
+
+func StrSliceAt(sl []string, i int) string {
+	if i < len(sl) {
+		return sl[i]
+	} else {
+		return ""
+	}
+}
+
+func StrSlice(sl []string, start int, end int) []string {
+	bound := func(i int) int { return IntMin(IntMax(0, i), len(sl)) }
+	start = bound(start)
+	end = bound(end)
+	return sl[start:end]
+}