add convenience constructors for arguments

arg.go

@@ -0,0 +1,41 @@
+package osc
+
+func StringArg(value string) Arg {
+	return Arg{Type: "s", Value: value}
+}
+
+func Int32Arg(value int32) Arg {
+	return Arg{Type: "i", Value: value}
+}
+
+func FloatArg(value float32) Arg {
+	return Arg{Type: "f", Value: value}
+}
+
+func BlobArg(value []byte) Arg {
+	return Arg{Type: "b", Value: value}
+}
+
+func TrueArg() Arg {
+	return Arg{Type: "T", Value: true}
+}
+
+func FalseArg() Arg {
+	return Arg{Type: "F", Value: false}
+}
+
+func NilArg() Arg {
+	return Arg{Type: "N", Value: nil}
+}
+
+func ColorArg(red, green, blue, alpha byte) Arg {
+	return Arg{Type: "r", Value: Color{r: red, g: green, b: blue, a: alpha}}
+}
+
+func Int64Arg(value int64) Arg {
+	return Arg{Type: "h", Value: value}
+}
+
+func DoubleArg(value float64) Arg {
+	return Arg{Type: "d", Value: value}
+}