Basic random capabilities

tstl/include/random.hpp

@@ -0,0 +1,76 @@
+//=======================================================================
+// Copyright Baptiste Wicht 2013-2016.
+// Distributed under the terms of the MIT License.
+// (See accompanying file LICENSE or copy at
+//  http://www.opensource.org/licenses/MIT)
+//=======================================================================
+
+#ifndef RANDOM_HPP
+#define RANDOM_HPP
+
+#include <types.hpp>
+
+namespace std {
+
+template<typename UIntType, UIntType a, UIntType c, UIntType m>
+struct linear_congruential_engine {
+    using result_type = UIntType;
+
+    static constexpr const result_type multiplier   = a;
+    static constexpr const result_type increment    = c;
+    static constexpr const result_type modulus      = m;
+    static constexpr const result_type default_seed = 1;
+
+    linear_congruential_engine(result_type seed = default_seed) : seed(seed){
+        // Generate the second result directly
+        (*this)();
+    }
+
+    result_type operator()(){
+        return seed = (multiplier * seed + increment) % modulus;
+    }
+
+    static constexpr result_type min(){
+        return 0;
+    }
+
+    static constexpr result_type max(){
+        return modulus - 1;
+    }
+
+private:
+    result_type seed;
+};
+
+using mnist_rand0 = linear_congruential_engine<uint32_t, 16807, 0, 2147483647>;
+using mnist_rand  = linear_congruential_engine<uint32_t, 48271, 0, 2147483647>;
+
+using default_random_engine = mnist_rand;
+
+template<typename IntType = int>
+struct uniform_int_distribution {
+    using result_type = IntType;
+
+    uniform_int_distribution(result_type a, result_type b) : a(a), b(b) {
+        //Nothing else to init
+    }
+
+    template<typename Generator>
+    result_type operator()(Generator& g) const {
+        static constexpr const auto input_range = Generator::max() - Generator::min();
+
+        const auto output_range = b - a;
+        const auto ratio        = input_range / output_range;
+        const auto offset       = a - Generator::min();
+
+        return (g() / ratio) + offset;
+    }
+
+private:
+    const result_type a;
+    const result_type b;
+};
+
+} //end of namespace std
+
+#endif