Re: [boost] Design question SafeFloat

Subject: Re: [boost] Design question SafeFloat
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2018-07-27 18:38:29

AMDG

On 07/26/2018 09:25 PM, Damian Vicino via Boost wrote:
> I'm working in simplifying safe_float to prepare it for future review.
> 
> For now I'm focusing in a C++17 compatible version.
> 
> Currently safefloat receives 2 template parameters:
> 
> template<typename FP, typename P>
> class safe_float ...
> 
> Where FP is the floating point value being made "safe", float, double, long
> double ...
> and P is a Policy of what to check and how to react.
> 
> <snip>
> These are the options I'm considering
> 
> 1) define typenames for each flag and assign them tuple of affected
> operations
> 
> class addition; <snip>
> 
> template<typename R>
> struct policy_x {
> using reporter=R;
> using overflow=tuple<addition>; <snip>
> };
> 
> 2) define typename by operation, passing class with constexprs of flags
> being evaluated
> 
> struct empty_check{
> static constexpr bool check_overflow=false; <snip>
> };
> 
> <snip>
> 
> 3) similar to 2, but using true_type, and false_type in place of constexpr
> variables.
> <snip>
> 4) other options?
> 

What about doing this the old-fashioned way:

constexpr check_policy_t empty_check = 0;
constexpr check_policy_t check_underflow = 0x1;
constexpr check_policy_t check_overflow = 0x2;
...

// with a bit of syntactic sugar:
struct operation_id {
  check_policy_t offset;
  constexpr check_policy_t operator=(check_policy_t value) const
  { return offset * value; }
};

constexpr operation_id
  addition=0x1,
  subtraction=0x100,
  multiplication=0x10000
  ...;

// Usage:
addition=check_overflow|subtraction=empty_check

In Christ,
Steven Watanabe