Index: CMakeLists.txt
===================================================================
--- CMakeLists.txt
+++ CMakeLists.txt
@@ -134,6 +134,7 @@
           ${CMAKE_BINARY_DIR}/lib/go/llgo-${LLGO_VERSION}/cgo
           ${CMAKE_BINARY_DIR}/bin/llgo-go${CMAKE_EXECUTABLE_SUFFIX}
           cmd/llgoi/llgoi.go
+          cmd/llgoi/pretty.go
   GOFLAGS "cc=${CMAKE_BINARY_DIR}/bin/clang"
           "cxx=${CMAKE_BINARY_DIR}/bin/clang++"
           "go=${CMAKE_BINARY_DIR}/bin/llgo-go"
Index: cmd/llgoi/llgoi.go
===================================================================
--- cmd/llgoi/llgoi.go
+++ cmd/llgoi/llgoi.go
@@ -125,7 +125,8 @@
 		return err
 	}
 
-	return nil
+	_, err = in.loadSourcePackageFromCode(prettySrc, "__llgo__/pretty", in.copts)
+	return err
 }
 
 func (in *interp) dispose() {
@@ -283,8 +284,7 @@
 
 	var code bytes.Buffer
 	fmt.Fprintf(&code, "package %s", pkgname)
-	code.WriteString("\n\nimport __fmt__ \"fmt\"\n")
-	code.WriteString("import __os__ \"os\"\n")
+	code.WriteString("\n\nimport __pretty__ \"__llgo__/pretty\"\n")
 
 	for _, pkg := range in.imports {
 		fmt.Fprintf(&code, "import %q\n", pkg.Path())
@@ -327,23 +327,17 @@
 		fmt.Fprintf(&code, " = %s\n\n", l.line)
 
 		code.WriteString("func init() {\n\t")
-		for i, t := range typs {
-			var varname, prefix string
+		for i := range typs {
+			var varname string
 			if len(l.assigns) != 0 && l.assigns[i] != "" {
 				if _, ok := in.scope[l.assigns[i]]; ok {
 					fmt.Fprintf(&code, "\t%s = __llgoiV%d\n", l.assigns[i], i)
 				}
 				varname = l.assigns[i]
-				prefix = l.assigns[i]
 			} else {
 				varname = fmt.Sprintf("__llgoiV%d", i)
-				prefix = fmt.Sprintf("#%d", i)
-			}
-			if _, ok := t.Underlying().(*types.Interface); ok {
-				fmt.Fprintf(&code, "\t__fmt__.Printf(\"%s %s (%%T) = %%+v\\n\", %s, %s)\n", prefix, t.String(), varname, varname)
-			} else {
-				fmt.Fprintf(&code, "\t__fmt__.Printf(\"%s %s = %%+v\\n\", %s)\n", prefix, t.String(), varname)
 			}
+			fmt.Fprintf(&code, "\t__pretty__.Print(%s)\n", varname)
 		}
 		code.WriteString("}")
 	} else {
Index: cmd/llgoi/pretty.go
===================================================================
--- /dev/null
+++ cmd/llgoi/pretty.go
@@ -0,0 +1,96 @@
+package main
+
+const prettySrc = `
+package pretty
+
+import (
+	"fmt"
+	"io"
+	"reflect"
+	"strconv"
+	"os"
+)
+
+func Print(val interface{}) {
+	Fprint(os.Stdout, val)
+}
+
+func Fprint(w io.Writer, val interface{}) {
+	printIndented(w, val, 0, 2, false)
+	fmt.Fprint(w, "\n")
+}
+
+func maybePrintConversion(w io.Writer, ty reflect.Type) func() {
+	if ty.PkgPath() != "" {
+		fmt.Fprint(w, ty.String() + "(")
+		return func() {
+			fmt.Fprint(w, ")")
+		}
+	} else {
+		return func() {}
+	}
+}
+
+func isSimpleType(ty reflect.Type) bool {
+	switch ty.Kind() {
+	case reflect.Bool,
+		reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
+		reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64,
+		reflect.Uintptr, reflect.Float32, reflect.Float64, reflect.Complex64, reflect.Complex128:
+		return true
+	default:
+		return false
+	}
+}
+
+func printIndented(w io.Writer, val interface{}, indent, ptrdepth int, aggElem bool) {
+	if val == nil {
+		fmt.Print("nil")
+	}
+
+	nl := func() {
+		fmt.Fprint(w, "\n")
+		for i := 0; i != indent; i++ {
+			fmt.Fprintf(w, "\t")
+		}
+	}
+
+	ty := reflect.TypeOf(val)
+	switch ty.Kind() {
+		case reflect.Bool,
+		reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
+		reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64,
+		reflect.Uintptr, reflect.Float32, reflect.Float64, reflect.Complex64, reflect.Complex128:
+			defer maybePrintConversion(w, ty)()
+			fmt.Fprint(w, val)
+
+		case reflect.Array:
+			if !aggElem {
+				fmt.Fprint(w, ty.String())
+			}
+			fmt.Fprint(w, "{")
+			if isSimpleType(ty.Elem()) {
+				for i := 0; i != ty.Len(); i++ {
+					if i != 0 {
+						fmt.Fprint(w, ", ")
+					}
+					fmt.Fprint(w, reflect.ValueOf(val).Index(i).Interface())
+				}
+			} else {
+				indent++
+				for i := 0; i != ty.Len(); i++ {
+					nl()
+					printIndented(w, reflect.ValueOf(val).Index(i).Interface(), indent, ptrdepth, true)
+					fmt.Fprint(w, ",")
+				}
+				indent--
+				nl()
+			}
+			fmt.Fprint(w, "}")
+
+		case reflect.String:
+			defer maybePrintConversion(w, ty)()
+			fmt.Fprint(w, strconv.Quote(val.(string)))
+	}
+}
+`