diff --git a/config/config.go b/config/config.go
index 4e2391d..711c255 100644
--- a/config/config.go
+++ b/config/config.go
@@ -84,12 +84,17 @@ var negativeZero = math.Copysign(0, -1)
 type Value interface {
 	value ()
 	fmt.Stringer
+	Equals (Value) bool
 }
 
 // ValueString is a string value.
 type ValueString string
 var _ Value = ValueString("")
 func (ValueString) value () { }
+func (value ValueString) Equals (other Value) bool {
+	other, ok := other.(ValueString)
+	return ok && value == other
+}
 func (value ValueString) String () string {
 	return fmt.Sprintf("\"%s\"", escape(string(value)))
 }
@@ -98,6 +103,10 @@ func (value ValueString) String () string {
 type ValueNumber float64
 var _ Value = ValueNumber(0)
 func (ValueNumber) value () { }
+func (value ValueNumber) Equals (other Value) bool {
+	other, ok := other.(ValueNumber)
+	return ok && value == other
+}
 func (value ValueNumber) String () string {
 	number := float64(value)
 	// the requirements I wrote said lossless in all cases. here's lossless
@@ -133,6 +142,10 @@ func (value ValueNumber) String () string {
 var _ Value = ValueBool(false)
 type ValueBool bool
 func (ValueBool) value () { }
+func (value ValueBool) Equals (other Value) bool {
+	other, ok := other.(ValueBool)
+	return ok && value == other
+}
 func (value ValueBool) String () string {
 	if value {
 		return "true"