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Last update Tue Jun 6 16:38:19 2006

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.