Properties
Every type and expression has properties that can be queried:
Expression | Value |
---|---|
int.sizeof | yields 4 |
float.nan | yields the floating point nan (Not A Number) value |
(float).nan | yields the floating point nan value |
(3).sizeof | yields 4 (because 3 is an int) |
2.sizeof | syntax error, since "2." is a floating point number |
int.init | default initializer for int's |
int.mangleof | yields the string "i" |
Properties for All Types
Property | Description |
---|---|
.init | initializer |
.sizeof | size in bytes (equivalent to C's sizeof(type)) |
.alignof | alignment size |
.mangleof | string representing the 'mangled' representation of the type |
Properties for Integral Types
Property | Description |
---|---|
.init | initializer (0) |
.max | maximum value |
.min | minimum value |
Properties for Floating Point Types
Property | Description |
---|---|
.init | initializer (NaN) |
.infinity | infinity value |
.nan | NaN value |
.dig | number of decimal digits of precision |
.epsilon | smallest increment to the value 1 |
.mant_dig | number of bits in mantissa |
.max_10_exp | maximum int value such that 10max_10_exp is representable |
.max_exp | maximum int value such that 2max_exp-1 is representable |
.min_10_exp | minimum int value such that 10min_10_exp is representable as a normalized value |
.min_exp | minimum int value such that 2min_exp-1 is representable as a normalized value |
.max | largest representable value that's not infinity |
.min | smallest representable normalized value that's not 0 |
.re | real part |
.im | imaginary part |
.init Property
.init produces a constant expression that is the default initializer. If applied to a type, it is the default initializer for that type. If applied to a variable or field, it is the default initializer for that variable or field. For example:
int a; int b = 1; typedef int t = 2; t c; t d = cast(t)3; int.init // is 0 a.init // is 0 b.init // is 1 t.init // is 2 c.init // is 2 d.init // is 3 struct Foo { int a; int b = 7; } Foo.a.init // is 0 Foo.b.init // is 7
Class and Struct Properties
Properties are member functions that can be syntactically treated as if they were fields. Properties can be read from or written to. A property is read by calling a method with no arguments; a property is written by calling a method with its argument being the value it is set to.
A simple property would be:
struct Foo { int data() { return m_data; } // read property int data(int value) { return m_data = value; } // write property private: int m_data; }
To use it:
int test() { Foo f; f.data = 3; // same as f.data(3); return f.data + 3; // same as return f.data() + 3; }
The absence of a read method means that the property is write-only. The absence of a write method means that the property is read-only. Multiple write methods can exist; the correct one is selected using the usual function overloading rules.
In all the other respects, these methods are like any other methods. They can be static, have different linkages, be overloaded with methods with multiple parameters, have their address taken, etc.
Note: Properties currently cannot be the lvalue of an op=, ++, or -- operator.