```C

struct Sass_Unknown {

  enum Sass_Tag tag;

};

struct Sass_Boolean {

  enum Sass_Tag tag;

  bool          value;

};

struct Sass_Number {

  enum Sass_Tag tag;

  double        value;

  char*         unit;

};

struct Sass_Color {

  enum Sass_Tag tag;

  double        r;

  double        g;

  double        b;

  double        a;

};

struct Sass_String {

  enum Sass_Tag tag;

  char*         value;

};

struct Sass_List {

  enum Sass_Tag       tag;

  enum Sass_Separator separator;

  size_t              length;

  // null terminated "array"

  union Sass_Value**  values;

};

struct Sass_Map {

  enum Sass_Tag        tag;

  size_t               length;

  struct Sass_MapPair* pairs;

};

struct Sass_Null {

  enum Sass_Tag tag;

};

struct Sass_Error {

  enum Sass_Tag tag;

  char*         message;

};

struct Sass_Warning {

  enum Sass_Tag tag;

  char*         message;

};

union Sass_Value {

  struct Sass_Unknown unknown;

  struct Sass_Boolean boolean;

  struct Sass_Number  number;

  struct Sass_Color   color;

  struct Sass_String  string;

  struct Sass_List    list;

  struct Sass_Map     map;

  struct Sass_Null    null;

  struct Sass_Error   error;

  struct Sass_Warning   warning;

};

struct Sass_MapPair {

  union Sass_Value* key;

  union Sass_Value* value;

};

```