2.11. Data Type Declarations

2.11. Data Type Declarations
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Starting in Qore 0.8.0, it is possible to restrict variables, class members, and function and method parameters to certain data types. This allows programmers to write safer code, as many more errors can be caught at parse time that would otherwise be caught at run time. Furthermore, providing type information to the parser allows Qore to implement performance optimizations by performing lookups and resolutions once at parse time rather than every time a variable or class member is accessed at run time.

When types are declared in a parameter list, functions and methods can be overloaded as well.

The types in the following table can be used as well as any class name or '*classname', meaning either the given class or NOTHING:

Table 2.8. Data Type Declaration Names

Name	Accepts Qore Type(s)	Returns Qore Type(s)	Description
`int`	Integer	Integer	Restricts values to Qore's Integer type.
`float`	Float	Float	Restricts values to Qore's Float type.
`bool`	Boolean	Boolean	Restricts values to Qore's Boolean type.
`string`	String	String	Restricts values to Qore's String type.
`date`	Date	Date	Restricts values to Qore's Date type; values may be either absolute or relative date/time values.
`binary`	Binary	Binary	Restricts values to Qore's Binary type.
`hash`	Hash	Hash	Restricts values to Qore's Hash type.
`list`	List	List	Restricts values to Qore's List type.
`object`	Object	Object	Restricts values to Qore's Object type.
`<classname>`	Object	Object	Restricts values to objects of the specific class given; either the class name can be given (ex: `Mutex` or a qualified path to the class: `Qore::Mutex`).
`null`	NULL	NULL	Restricts values to Qore's NULL type; this type has few (if any) practical applications and has been included for completeness' sake.
`nothing`	NOTHING	NOTHING	Restricts values to Qore's NOTHING type; this type is mostly useful for declaring that a function or method returns no value.
`timeout`	Integer, Date	Integer	Accepts Integer, Date and converts dates to an integer value representing milliseconds and returns the integer; incoming integers are assumed to represent milliseconds.
`softint`	Integer, Float, Boolean, String, NULL	Integer	Accepts Integer, Float, Boolean, String, NULL and converts non-integer values to an integer and returns the integer.
`softfloat`	Integer, Float, Boolean, String, NULL	Float	Accepts Integer, Float, Boolean, String, NULL and converts non-float values to a float and returns the new value.
`softbool`	Integer, Float, Boolean, String, NULL	Boolean	Accepts Integer, Float, Boolean, String, NULL and converts non-boolean values to a boolean and returns the new value.
`softstring`	Integer, Float, Boolean, String, NULL	String	Accepts Integer, Float, Boolean, String, NULL and converts non-string values to a string and returns the new value.
`softdate`	Integer, Float, Boolean, String, Date, NULL	Date	Accepts Integer, Float, Boolean, String, Date, and NULL and converts non-date values to a date and returns the new value.
`softlist`	all types	List	Accepts all types; NOTHING is returned as an empty list; a list is returned unchanged, and any other type is returned as the first element of a new list.
`*int`	Integer or NOTHING	same as received	Restricts values to Qore's Integer or NOTHING types.
`*float`	Float or NOTHING	same as received	Restricts values to Qore's Float or NOTHING types.
`*bool`	Boolean or NOTHING	same as received	Restricts values to Qore's Boolean or NOTHING types.
`*string`	String or NOTHING	same as received	Restricts values to Qore's String or NOTHING types.
`*date`	Date or NOTHING	same as received	Restricts values to Qore's Date or NOTHING type; values may be either absolute or relative date/time values.
`*binary`	Binary or NOTHING	same as received	Restricts values to Qore's Binary or NOTHING types.
`*hash`	Hash or NOTHING	same as received	Restricts values to Qore's Hash or NOTHING types.
`*list`	List or NOTHING	same as received	Accepts either a List or NOTHING.
`*data`	String, Binary, or NOTHING	same as received	Restricts input to String, Binary, or NOTHING and returns the same type.
`*code`	Closure, Call Reference or NOTHING	same as received	Restricts values to closures, call references and NOTHING.
`*timeout`	Integer, Date or NOTHING	Integer or NOTHING	Accepts Integer, Date and converts dates to an integer value representing milliseconds and returns the integer; incoming integers are assumed to represent milliseconds. If no value is passed, then NOTHING is returned.
`*softint`	Integer, Float, Boolean, String, NULL or NOTHING	Integer or NOTHING	Accepts Integer, Float, Boolean, String, NULL and converts non-integer values to an integer and returns the integer. If no value is passed, then NOTHING is returned.
`*softfloat`	Integer, Float, Boolean, String, NULL or NOTHING	Float or NOTHING	Accepts Integer, Float, Boolean, String, NULL and converts non-float values to a float and returns the new value. If no value is passed, then NOTHING is returned.
`*softbool`	Integer, Float, Boolean, String, NULL or NOTHING	Boolean or NOTHING	Accepts Integer, Float, Boolean, String, NULL and converts non-boolean values to a boolean and returns the new value. If no value is passed, then NOTHING is returned.
`*softstring`	Integer, Float, Boolean, String, NULL or NOTHING	String or NOTHING	Accepts Integer, Float, Boolean, String, NULL and converts non-string values to a string and returns the new value. If no value is passed, then NOTHING is returned.
`*softdate`	Integer, Float, Boolean, String, Date, NULL or NOTHING	Date or NOTHING	Accepts Integer, Float, Boolean, String, Date, and NULL and converts non-date values to a date and returns the new value. If no value is passed, then NOTHING is returned.
`*softlist`	all types	List or NOTHING	Accepts all types; NOTHING and list values are returned as the same value; any other type is returned as the first element of a new list.
`any`	any	same as received	Provides no restrictions on the type of value it receives and returns the same value.
`data`	String or Binary	same as received	Restricts input to String and Binary and returns the same type.
`code`	Closure, Call Reference	same as received	Restricts values to closures and call references.
`reference`	reference to an lvalue	same as received	Restricts values to references to lvalues; currently only usable in function or method parameters.
`closure`	Closure, Call Reference	same as received	Does not restrict value to just closures, but rather also allows call references. Synonym for `code`.
`callref`	Closure, Call Reference	same as received	Does not restrict value to just call references, but rather also allows closures. Synonym for `code`.

Complex types (hash of lists, reference to string, etc) are currently not possible to declare.

2.11.1. Overloading

Functions and methods can be overloaded if parameter types are declared as in the following example:

int sub example(int $i) {
    printf("i=%d\n", $i);
    return $i + 1;
}

string sub example(string $str) {
    printf("str=%s\n", $str);
    return $str + "foo";
}

In this case, the first version (example(int)) will be executed if called with an integer argument, and the second (example(string)) if called with a string argument.

Class methods may also be overloaded, but note that destructor(), copy(), methodGate(), memberGate(), and memberNotification() methods may not be overloaded (see Classes for more information).

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