text: // Copyright (c) 2000-2020, Heiko Bauke
  // All rights reserved.
  //
  // Redistribution and use in source and binary forms, with or without
  // modification, are permitted provided that the following conditions
  // are met:
  //
  //   * Redistributions of source code must retain the above copyright
  //     notice, this list of conditions and the following disclaimer.
  //
  //   * Redistributions in binary form must reproduce the above
  //     copyright notice, this list of conditions and the following
  //     disclaimer in the documentation and/or other materials provided
  //     with the distribution.
  //
  //   * Neither the name of the copyright holder nor the names of its
  //     contributors may be used to endorse or promote products derived
  //     from this software without specific prior written permission.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  // FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  // COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
  // INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  // (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
  // SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  // HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  // STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  // ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
  // OF THE POSSIBILITY OF SUCH DAMAGE.
  
  #if !(defined TRNG_UNIFORM_DIST_HPP)
  
  #define TRNG_UNIFORM_DIST_HPP
  
  #include <trng/cuda.hpp>
  #include <trng/limits.hpp>
  #include <trng/utility.hpp>
  #include <ostream>
  #include <istream>
  #include <iomanip>
  #include <cerrno>
  #include <ciso646>
  
  namespace trng {
  
    // uniform random number generator class
    template<typename float_t = double>
    class uniform_dist {
    public:
      using result_type = float_t;
  
      class param_type {
      private:
        result_type a_{0}, b_{1}, d_{1};
        TRNG_CUDA_ENABLE
        result_type d() const { return d_; }
  
      public:
        TRNG_CUDA_ENABLE
        result_type a() const { return a_; }
        TRNG_CUDA_ENABLE
        void a(result_type a_new) {
          a_ = a_new;
          d_ = b_ - a_;
        }
        TRNG_CUDA_ENABLE
        result_type b() const { return b_; }
        TRNG_CUDA_ENABLE
        void b(result_type b_new) {
          b_ = b_new;
          d_ = b_ - a_;
        }
        TRNG_CUDA_ENABLE
        param_type() = default;
        TRNG_CUDA_ENABLE
        explicit param_type(result_type a, result_type b) : a_(a), b_(b), d_(b - a) {}
  
        friend class uniform_dist<float_t>;
  
        // Streamable concept
        template<typename char_t, typename traits_t>
        friend std::basic_ostream<char_t, traits_t> &operator<<(
            std::basic_ostream<char_t, traits_t> &out, const param_type &P) {
          std::ios_base::fmtflags flags(out.flags());
          out.flags(std::ios_base::dec | std::ios_base::fixed | std::ios_base::left);
          out << '(' << std::setprecision(math::numeric_limits<float_t>::digits10 + 1) << P.a()
              << ' ' << P.b() << ')';
          out.flags(flags);
          return out;
        }
  
        template<typename char_t, typename traits_t>
        friend std::basic_istream<char_t, traits_t> &operator>>(
            std::basic_istream<char_t, traits_t> &in, param_type &P) {
          float_t a, b;
          std::ios_base::fmtflags flags(in.flags());
          in.flags(std::ios_base::dec | std::ios_base::fixed | std::ios_base::left);
          in >> utility::delim('(') >> a >> utility::delim(' ') >> b >> utility::delim(')');
          if (in)
            P = param_type(a, b);
          in.flags(flags);
          return in;
        }
      };
  
    private:
      param_type P;
  
    public:
      // constructor
      TRNG_CUDA_ENABLE
      uniform_dist(result_type a, result_type b) : P{a, b} {}
      TRNG_CUDA_ENABLE
      explicit uniform_dist(const param_type &P) : P{P} {}
      // reset internal state
      TRNG_CUDA_ENABLE
      void reset() {}
      // random numbers
      template<typename R>
      TRNG_CUDA_ENABLE result_type operator()(R &r) {
        return P.d() * utility::uniformco<result_type>(r) + P.a();
      }
      template<typename R>
      TRNG_CUDA_ENABLE result_type operator()(R &r, const param_type &P) {
        uniform_dist g(P);
        return g(r);
      }
      // property methods
      TRNG_CUDA_ENABLE
      result_type min() const { return P.a(); }
      TRNG_CUDA_ENABLE
      result_type max() const { return P.b(); }
      TRNG_CUDA_ENABLE
      param_type param() const { return P; }
      TRNG_CUDA_ENABLE
      void param(const param_type &p_new) { P = p_new; }
      TRNG_CUDA_ENABLE
      result_type a() const { return P.a(); }
      TRNG_CUDA_ENABLE
      void a(result_type a_new) { P.a(a_new); }
      TRNG_CUDA_ENABLE
      result_type b() const { return P.b(); }
      TRNG_CUDA_ENABLE
      void b(result_type b_new) { P.b(b_new); }
      // probability density function
      TRNG_CUDA_ENABLE
      result_type pdf(result_type x) const {
        if (x < P.a() or x >= P.b())
          return 0.0;
        return 1.0 / P.d();
      }
      // cumulative density function
      TRNG_CUDA_ENABLE
      result_type cdf(result_type x) const {
        if (x < P.a())
          return 0;
        if (x >= P.b())
          return 1;
        return (x - P.a()) / P.d();
      }
      // inverse cumulative density function
      TRNG_CUDA_ENABLE
      result_type icdf(result_type x) const {
        if (x < 0 or x > 1) {
  #if !(defined __CUDA_ARCH__)
          errno = EDOM;
  #endif
          return math::numeric_limits<result_type>::quiet_NaN();
        }
        return x * P.d() + P.a();
      }
    };
  
    // -------------------------------------------------------------------
  
    // EqualityComparable concept
    template<typename float_t>
    TRNG_CUDA_ENABLE bool operator==(const typename uniform_dist<float_t>::param_type &P1,
                                     const typename uniform_dist<float_t>::param_type &P2) {
      return P1.a() == P2.a() and P1.b() == P2.b();
    }
  
    template<typename float_t>
    TRNG_CUDA_ENABLE bool operator!=(const typename uniform_dist<float_t>::param_type &P1,
                                     const typename uniform_dist<float_t>::param_type &P2) {
      return not(P1 == P2);
    }
  
    // -------------------------------------------------------------------
  
    // EqualityComparable concept
    template<typename float_t>
    TRNG_CUDA_ENABLE bool operator==(const uniform_dist<float_t> &g1,
                                     const uniform_dist<float_t> &g2) {
      return g1.param() == g2.param();
    }
  
    template<typename float_t>
    TRNG_CUDA_ENABLE bool operator!=(const uniform_dist<float_t> &g1,
                                     const uniform_dist<float_t> &g2) {
      return g1.param() != g2.param();
    }
  
    // -------------------------------------------------------------------
  
    // Streamable concept
    template<typename char_t, typename traits_t, typename float_t>
    std::basic_ostream<char_t, traits_t> &operator<<(std::basic_ostream<char_t, traits_t> &out,
                                                     const uniform_dist<float_t> &g) {
      std::ios_base::fmtflags flags(out.flags());
      out.flags(std::ios_base::dec | std::ios_base::fixed | std::ios_base::left);
      out << "[uniform " << g.param() << ']';
      out.flags(flags);
      return out;
    }
  
    template<typename char_t, typename traits_t, typename float_t>
    std::basic_istream<char_t, traits_t> &operator>>(std::basic_istream<char_t, traits_t> &in,
                                                     uniform_dist<float_t> &g) {
      typename uniform_dist<float_t>::param_type P;
      std::ios_base::fmtflags flags(in.flags());
      in.flags(std::ios_base::dec | std::ios_base::fixed | std::ios_base::left);
      in >> utility::ignore_spaces() >> utility::delim("[uniform ") >> P >> utility::delim(']');
      if (in)
        g.param(P);
      in.flags(flags);
      return in;
    }
  
  }  // namespace trng
  
  #endif
  