types: add Stringer implementation for Tuple

Signed-off-by: Sebastien Binet <[email protected]>

types/tuple.go

@@ -4,6 +4,11 @@
 
 package types
 
+import (
+	"fmt"
+	"strings"
+)
+
 type Tuple []interface{}
 
 func NewTupleFromSlice(slice []interface{}) *Tuple {
@@ -18,3 +23,22 @@ func (t *Tuple) Get(i int) interface{} {
 func (t *Tuple) Len() int {
 	return len(*t)
 }
+
+func (t *Tuple) String() string {
+	if t == nil {
+		return "nil"
+	}
+	o := new(strings.Builder)
+	o.WriteString("(")
+	for i, v := range *t {
+		if i > 0 {
+			o.WriteString(", ")
+		}
+		fmt.Fprintf(o, "%v", v)
+	}
+	if t.Len() == 1 {
+		o.WriteString(",")
+	}
+	o.WriteString(")")
+	return o.String()
+}

types/tuple_test.go

@@ -0,0 +1,28 @@
+// Copyright 2023 NLP Odyssey Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package types
+
+import (
+	"bytes"
+	"fmt"
+	"testing"
+)
+
+func TestTupleStringer(t *testing.T) {
+	tuple := func(sli ...interface{}) *Tuple {
+		return NewTupleFromSlice(sli)
+	}
+
+	tup := tuple(tuple(), tuple(1), tuple(2, 3), tuple(tuple(4, 5), 6))
+
+	buf := new(bytes.Buffer)
+	fmt.Fprintf(buf, "%v", tup)
+	got := buf.String()
+	want := "((), (1,), (2, 3), ((4, 5), 6))"
+
+	if got != want {
+		t.Fatalf("got= %q\nwant=%q", got, want)
+	}
+}