// Copyright 2011 The Go 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 types2

// A Tuple represents an ordered list of variables; a nil *Tuple is a valid (empty) tuple.
// Tuples are used as components of signatures and to represent the type of multiple
// assignments; they are not first class types of Go.
type Tuple struct {
	vars []*Var
}

// NewTuple returns a new tuple for the given variables.
func NewTuple(x ...*Var) *Tuple {
	if len(x) > 0 {
		return &Tuple{vars: x}
	}
	// TODO(gri) Don't represent empty tuples with a (*Tuple)(nil) pointer;
	//           it's too subtle and causes problems.
	return nil
}

// Len returns the number variables of tuple t.
func (t *Tuple) Len() int {
	if t != nil {
		return len(t.vars)
	}
	return 0
}

// At returns the i'th variable of tuple t.
func (t *Tuple) At(i int) *Var { return t.vars[i] }

func (t *Tuple) Underlying() Type { return t }
func (t *Tuple) String() string   { return TypeString(t, nil) }