On 2/27/2011 12:10 PM, Peter Lundgren wrote:
I'd like to define a type Ordinal which behaves like an int (using a struct or
alias) that represents the 26 letters, A-Z, with the numbers 1-26. Then, I
would like to be able to coerce between chars and Ordinals appropriately.
chars and ints already have the ability to coerce between each other using the
appropriate ASCII values. So, really, I'd just like to define a type that
overrides this behavior.
As far as I can tell, the place to define such rules is with opCast!, but I'm
at a loss for how to add additional rules to built in types.
I haven't tried anything like this yet (I'm still pretty new to D), but
I think something like this is the best you'll be able to do:
struct Ordinal
{
this(int value) { m_Value = value; }
this(dchar ch) { m_Value = ch - 'a' + 1; } // add range checks as
appropriate
alias this m_Value;
T opCast(T)() if (T is dchar) { return m_Value + 'a' - 1; }
// add more operators as appropriate
private:
int m_Value;
}
