Properties
Every type and expression has properties that can be queried: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
.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
.init initializer (0) .max maximum value .min minimum value
Properties for Floating Point Types
.init initializer (NaN) .infinity infinity value .nan NaN value .dig number of decimal digits of precision .epsilon smallest increment .mant_dig number of bits in mantissa .max_10_exp maximum exponent as power of 10 .max_exp maximum exponent as power of 2 .min_10_exp minimum exponent as power of 10 .min_exp minimum exponent as power of 2 .max largest representable value that's not infinity .min smallest representable 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.