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MG Mud User88f12472016-06-24 23:31:02 +02001CONCEPT
2 unions
3
4DESCRIPTION
5 Unions types are a declaration at compile time that a variable,
6 function parameter or function return value can be one of
7 several types.
8
9 Except for type checks using #pragma rtt_checks they have no
10 impact at runtime. There is no runtime union type, the concrete
11 value type is one of the possibilities of the union type.
12
13 Union types have no type names for themselves, they are declared
14 anonymously with the declaration of the variable, function
15 parameter or return type:
16
17 int|string var;
18 int|float fun(object|closure f);
19
20 When using union types as array member types they must be
21 enclosed with < >:
22
23 <int|string>* arr; /* An array of ints and strings. */
24 int*|string* arr; /* Either an array of ints or
25 an array of strings. */
26
27 /* There must be a whitespace between two consecutive <
28 to be not confused with the << operator: */
29 < <int|string>*|object >* arr;
30