defaultCurrency implenemted for unknown currencies + ChangeDefaultCur…

…rency(), issue Rhymond#69

currency.go

@@ -15,6 +15,9 @@ type Currency struct {
 	Thousand    string
 }
 
+// default currency
+var defaultCurrency = "USD"
+
 // currencies represents a collection of currency.
 var currencies = map[string]*Currency{
 	"AED": {Decimal: ".", Thousand: ",", Code: "AED", Fraction: 2, NumericCode: "784", Grapheme: ".\u062f.\u0625", Template: "1 $"},
@@ -211,6 +214,14 @@ func GetCurrency(code string) *Currency {
 	return currencies[code]
 }
 
+// ChangeDefaultCurrency changes the default currency
+func ChangeDefaultCurrency(code string) {
+	if _, ok := currencies[code]; ok {
+		defaultCurrency = code
+	}
+	return
+}
+
 // Formatter returns currency formatter representing
 // used currency structure.
 func (c *Currency) Formatter() *Formatter {
@@ -235,7 +246,7 @@ func (c *Currency) get() *Currency {
 		return curr
 	}
 
-	return c.getDefault()
+	return currencies[defaultCurrency]
 }
 
 func (c *Currency) equals(oc *Currency) bool {

currency_test.go

@@ -27,11 +27,21 @@ func TestCurrency_Get1(t *testing.T) {
 	code := "RANDOM"
 	c := newCurrency(code).get()
 
-	if c.Grapheme != code {
-		t.Errorf("Expected %s got %s", c.Grapheme, code)
+	if c.Code != defaultCurrency {
+		t.Errorf("Expected %s got %s", c.Code, code)
 	}
+
 }
 
+func TestCurrency_Get2(t *testing.T) {
+	code := "RANDOM"
+
+	ChangeDefaultCurrency("GBP")
+	c1 := newCurrency(code).get()
+	if c1.Code != defaultCurrency {
+		t.Errorf("Expected %s got %s", c1.Code, defaultCurrency)
+	}
+}
 func TestCurrency_Equals(t *testing.T) {
 	tcs := []struct {
 		code  string