libtrilinos-teuchos-dev 12.10.1-3 / usr / include / trilinos / Teuchos_MatrixMarket_SetScientific.hpp

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#ifndef __Teuchos_MatrixMarket_SetScientific_hpp
#define __Teuchos_MatrixMarket_SetScientific_hpp

#include <Teuchos_ConfigDefs.hpp>
#include <Teuchos_as.hpp>
#include <Teuchos_ScalarTraits.hpp>
#include <string>


namespace Teuchos {
  namespace MatrixMarket {
    namespace details {
      /// \class SetScientificImpl
      /// \brief Implementation of SetScientific.
      ///
      /// This class is an implementation detail of SetScientific.
      /// Users should use SetScientific, not this class.
      ///
      /// \tparam Scalar A type for which
      ///   Teuchos::ScalarTraits<Scalar> has a specialization.
      /// \tparam isFloatingPoint Whether Scalar is a floating-point
      ///   type (either real or complex).
      template<class Scalar, const bool isFloatingPoint>
      class SetScientificImpl {
      public:
        //! The Scalar type with which SetScientific was specialized.
        typedef Scalar scalar_type;
        /// Constructor.
        ///
        /// \param out [in/out] Output stream to which to apply the
        ///   scientific notation flags.
        SetScientificImpl (std::ostream& out);
        /// Destructor.
        ///
        /// The destructor sets the output stream's flags back to
        /// their original state, that is, the state before the
        /// constructor of this object was called.
        ~SetScientificImpl ();
      };

      /// Partial specialization of SetScientificImpl for floating-point types.
      ///
      /// This class currently requires that std::log10() take
      /// arguments of type Scalar.  This may be relaxed in the future
      /// if Teuchos::ScalarTraits gets its own log10() method.
      template<class Scalar>
      class SetScientificImpl<Scalar, true> {
      public:
        typedef Scalar scalar_type;

        SetScientificImpl (std::ostream& out) :
          out_ (out), originalFlags_ (out.flags())
        {
          typedef Teuchos::ScalarTraits<scalar_type> STS;
          typedef typename STS::magnitudeType magnitude_type;
          typedef Teuchos::ScalarTraits<magnitude_type> STM;

          // Print floating-point values in scientific notation.
          out << std::scientific;

          // We're writing decimal digits, so compute the number of
          // digits we need to get reasonable accuracy when reading
          // values back in.
          //
          // There is actually an algorithm, due to Guy Steele (yes,
          // Java's Guy Steele) et al., for idempotent printing of
          // finite-length floating-point values.  We should actually
          // implement that algorithm, but I don't have time for that
          // now.  Currently, I just print no more than (one decimal
          // digit more than (the number of decimal digits justified
          // by the precision of magnitude_type)).
          //
          // We need to use STM's log10() rather than (say) std::log10
          // here, because STM::base() returns a magnitude_type, not
          // one of C++'s standard integer types.
          const magnitude_type numDecDigits = STM::t() * STM::log10 (STM::base());

          // Round and add one.  The cast to int should not overflow
          // unless STM::t() is _extremely_ large, so we don't need to
          // check for that case here.
          const magnitude_type one = STM::one();
          const magnitude_type two = one + one;
          // Cast from magnitude_type to int, since std::ostream's
          // precision() method expects an int input.
          const int prec = 1 + Teuchos::as<int> (magnitude_type((two*numDecDigits + one) / two));

          // Set the number of (decimal) digits after the decimal
          // point to print.
          out.precision (prec);
        }

        ~SetScientificImpl () {
          out_.flags (originalFlags_);
        }

      private:
        //! The output stream to which to apply flags.
        std::ostream& out_;

        //! The output stream's original flags.
        std::ios_base::fmtflags originalFlags_;
      };

      //! Partial specialization of SetScientificImpl for non-floating-point types.
      template<class Scalar>
      class SetScientificImpl<Scalar, false> {
      public:
        typedef Scalar scalar_type;
        SetScientificImpl (std::ostream&) {}
        ~SetScientificImpl () {}
      };

      /// \class SetScientific
      /// \brief Temporarily make an output stream use scientific
      ///   notation with sufficient precision.
      ///
      /// On construction, apply the necessary flags to the given
      /// output stream so that floating-point numbers are written in
      /// scientific notation with precision (dependent on the Scalar
      /// type) sufficient to ensure that they can be read in with the
      /// same value.  On destruction, restore the original
      /// (pre-construction) flags to the output stream.
      ///
      /// This makes SetScientific good for scope-protected alteration
      /// of the output stream's flags; no matter how the scope exits
      /// (normally or by a thrown exception), the original flags will
      /// be restored.  Hence, "temporarily" (or even "politely"): we
      /// restore the original flags on scope exit.
      ///
      /// \tparam Scalar A floating-point type, either real or
      ///   complex, for which Teuchos::ScalarTraits<Scalar> has a
      ///   specialization.
      template<class Scalar>
      class SetScientific :
	public SetScientificImpl<Scalar, ! Teuchos::ScalarTraits<Scalar>::isOrdinal> {
      private:
	//! Parent class of this class.
	typedef SetScientificImpl<Scalar, ! Teuchos::ScalarTraits<Scalar>::isOrdinal> base_type;

      public:
        //! The Scalar type with which SetScientific was specialized.
        typedef Scalar scalar_type;

        /// Constructor.
        ///
        /// \param out [in/out] Output stream to which to apply the
        ///   scientific notation flags.
        SetScientific (std::ostream& out) : base_type (out) {}

        /// Destructor.
        ///
        /// The destructor sets the output stream's flags back to
        /// their original state, that is, the state before the
        /// constructor of this object was called.
        ~SetScientific () {
	  // Parent class' destructor will be called automatically.
	}
      };

//       // Specialization for Scalar=int.  Specializations for built-in
//       // integer types let Tpetra::MatrixMarket::Reader or
//       // Tpetra::MatrixMarket::Writer work with a Tpetra::CrsMatrix
//       // whose Scalar template parameter is a built-in integer type.
//       // These specializations are trivial because there are no
//       // decimal digits to print.
//       template<>
//       class SetScientific<int> {
//       public:
//         typedef int scalar_type;
//         SetScientific (std::ostream& out) {}
//         ~SetScientific () {}
//       };

//       // Specialization for Scalar=unsigned int.
//       template<>
//       class SetScientific<unsigned int> {
//       public:
//         typedef unsigned int scalar_type;
//         SetScientific (std::ostream& out) {}
//         ~SetScientific () {}
//       };

//       // Specialization for Scalar=long.
//       template<>
//       class SetScientific<long> {
//       public:
//         typedef long scalar_type;
//         SetScientific (std::ostream& out) {}
//         ~SetScientific () {}
//       };

//       // Specialization for Scalar=unsigned long.
//       template<>
//       class SetScientific<unsigned long> {
//       public:
//         typedef unsigned long scalar_type;
//         SetScientific (std::ostream& out) {}
//         ~SetScientific () {}
//       };

// #ifdef HAVE_TEUCHOS_LONG_LONG_INT

//       // Specialization for Scalar=long long.
//       template<>
//       class SetScientific<long long> {
//       public:
//         typedef long long scalar_type;
//         SetScientific (std::ostream& out) {}
//         ~SetScientific () {}
//       };

//       // Specialization for Scalar=unsigned long long.
//       template<>
//       class SetScientific<unsigned long long> {
//       public:
//         typedef unsigned long long scalar_type;
//         SetScientific (std::ostream& out) {}
//         ~SetScientific () {}
//       };

// #endif // HAVE_TEUCHOS_LONG_LONG_INT


    } // namespace details
  } // namespace MatrixMarket
} // namespace Teuchos

#endif // __Teuchos_MatrixMarket_SetScientific_hpp