Re: [boost] Numeric constants

John Maddock wrote:

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template <class T> T pi();

I have a fixed-point class. What actually happens when I call pi<fixed>() ?

Currently with Boost.Math if you call:

pi<my_UDT>()

then internally it does a lexical_cast from a string containing ~100 decimal digits to my_UDT.

OK, I suppose that makes sense in general. My fixed class doesn't have operator<<,>> unfortunately, since I've never needed them for anything else.

And finally don't forget that you could add user-defined full specialisations of the templates for my_UDT if my_UDT provides its own interfaces to various constants.

Can I specialise all_constants<my_type> to cast from double without having to write out all of the constants individually? Phil.