Re: [Boost-users] [multiprecision] Empty intervals and intervalswithNaN check

Subject: Re: [Boost-users] [multiprecision] Empty intervals and intervalswithNaN check
From: John Maddock (john_at_[hidden])
Date: 2013-11-21 08:04:04

> No, the class is a very thin wrapper around mpfi so there's practically no 
> error checking.  I really should add some error checks to the functions 
> that create new intervals (i.e. assignment operators from two 
> "components"): I'll do that shortly.

Here's the patch for better error checks going in Trunk, hopefully that 
should stop most invalid intervals from ever occurring in the first place:

Index: mpfi.hpp
===================================================================
--- mpfi.hpp (revision 86537)
+++ mpfi.hpp (working copy)
@@ -179,6 +179,8 @@
    }
    mpfi_float_imp& operator = (const char* s)
    {
+      using default_ops::eval_fpclassify;
+
       if(m_data[0].left._mpfr_d == 0)
          mpfi_init2(m_data, multiprecision::detail::digits10_2_2(digits10 ? 
digits10 : get_default_precision()));

@@ -203,7 +205,22 @@
             part.erase();
          b = part.c_str();

-         mpfi_interv_fr(m_data, a.data(), b.data());
+         if(eval_fpclassify(a) == FP_NAN)
+         {
+            mpfi_set_fr(this->data(), a.data());
+         }
+         else if(eval_fpclassify(b) == FP_NAN)
+         {
+            mpfi_set_fr(this->data(), b.data());
+         }
+         else
+         {
+            if(a.compare(b) > 0)
+            {
+               BOOST_THROW_EXCEPTION(std::runtime_error("Attempt to create 
interval with invalid range (start is greater than end)."));
+            }
+            mpfi_interv_fr(m_data, a.data(), b.data());
+         }
       }
       else if(mpfi_set_str(m_data, s, 10) != 0)
       {
@@ -745,7 +762,23 @@
 template <unsigned D1, unsigned D2, mpfr_allocation_type AllocationType>
 inline void assign_components(mpfi_float_backend<D1>& result, const 
mpfr_float_backend<D2, AllocationType>& a, const mpfr_float_backend<D2, 
AllocationType>& b)
 {
-   mpfi_interv_fr(result.data(), a.data(), b.data());
+   using default_ops::eval_fpclassify;
+   if(eval_fpclassify(a) == FP_NAN)
+   {
+      mpfi_set_fr(result.data(), a.data());
+   }
+   else if(eval_fpclassify(b) == FP_NAN)
+   {
+      mpfi_set_fr(result.data(), b.data());
+   }
+   else
+   {
+      if(a.compare(b) > 0)
+      {
+         BOOST_THROW_EXCEPTION(std::runtime_error("Attempt to create 
interval with invalid range (start is greater than end)."));
+      }
+      mpfi_interv_fr(result.data(), a.data(), b.data());
+   }
 }

 template <unsigned Digits10, class V>

John.