Re: [Boost-users] deleting operators to forbid mixed arithmetic? [multiprecision]

Subject: Re: [Boost-users] deleting operators to forbid mixed arithmetic? [multiprecision]
From: John Maddock (jz.maddock_at_[hidden])
Date: 2017-08-12 17:13:54

On 12/08/2017 00:53, Dani Brake via Boost-users wrote:
> Hi,
> I'd like to forbid multiplication of Boost.Multiprecision floating 
> point numbers by doubles.  Any tips?  I think I want to delete a 
> family of operator*s, but am having a hard time coming up with which ones.

All the operators are enable_if'ed on "is_compatible_arithmetic_type<V, 
M>::value" where V is the arithmetic type and M is the multiprecision 
type.  The trait is defined in 
boost/multiprecision/detail/number_base.hpp as:

template <class T, class Num>
struct is_compatible_arithmetic_type
    : public mpl::bool_<
          is_convertible<T, Num>::value
          && !is_same<T, Num>::value
          && !is_number_expression<T>::value>
{};

So in principle you just define a full or partial specialization, for 
example:

template <class Backend>
struct is_compatible_arithmetic_type<double, number<Backend> > : public 
mpl::false_ {};

and then cross your fingers and hope for the best ;)

This is untried, and it's quite likely there will be collateral damage - 
things which should compile but don't any more because they multiply by 
0.5 or something.

HTH, John.

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