Modernize RNG to support std::uniform_random_bit_generator requirement

src/gnu/CMakeLists.txt

@@ -15,7 +15,6 @@ add_library(
   Poisson.cpp
   Rand.cpp
   Random.cpp
-  RNG.cpp
   Uniform.cpp
   Weibull.cpp)
 set_property(TARGET nrngnu PROPERTY POSITION_INDEPENDENT_CODE ON)

src/gnu/RNG.h

@@ -1,56 +1,28 @@
-// This may look like C code, but it is really -*- C++ -*-
-/* 
-Copyright (C) 1988 Free Software Foundation
-    written by Dirk Grunwald ([email protected])
-
-This file is part of the GNU C++ Library.  This library is free
-software; you can redistribute it and/or modify it under the terms of
-the GNU Library General Public License as published by the Free
-Software Foundation; either version 2 of the License, or (at your
-option) any later version.  This library is distributed in the hope
-that it will be useful, but WITHOUT ANY WARRANTY; without even the
-implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
-PURPOSE.  See the GNU Library General Public License for more details.
-You should have received a copy of the GNU Library General Public
-License along with this library; if not, write to the Free Software
-Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
-*/
 #pragma once
-/*
- * int32_t and uint32_t have been defined by the configure procedure.  Just
- * use these in place of the ones that libg++ used to provide. 
- */
 #include <cstdint>
-#include <cassert>
-#include <cmath>
-
-union PrivateRNGSingleType {		   	// used to access floats as unsigneds
-    float s;
-    uint32_t u;
-};
-
-union PrivateRNGDoubleType {		   	// used to access doubles as unsigneds
-    double d;
-    uint32_t u[2];
-};
+#include <limits>
 
-//
-// Base class for Random Number Generators.
-//
 class RNG {
-    static PrivateRNGSingleType singleMantissa;	// mantissa bit vector
-    static PrivateRNGDoubleType doubleMantissa;	// mantissa bit vector
 public:
-    RNG();
-    virtual ~RNG();
-    //
+    using result_type = std::uint32_t;
+
+    RNG() = default;
+    virtual ~RNG() = default;
+
     // Return a long-words word of random bits
-    //
-    virtual uint32_t asLong() = 0;
+    virtual result_type asLong() = 0;
     virtual void reset() = 0;
-    //
-    // Return random bits converted to either a float or a double
-    //
-    virtual float asFloat();
-    virtual double asDouble();
+
+    // Return random bits converted to a double
+    virtual double asDouble() = 0;
+
+    static constexpr result_type min() {
+        return std::numeric_limits<result_type>::min();
+    }
+    static constexpr result_type max() {
+        return std::numeric_limits<result_type>::max();
+    }
+    result_type operator()() {
+        return asLong();
+    }
 };