refactor: reorganize code and use c api (#133)

rng.hpp

@@ -0,0 +1,35 @@
+#ifndef __RNG_H__
+#define __RNG_H__
+
+#include <random>
+#include <vector>
+
+class RNG {
+public:
+    virtual void manual_seed(uint64_t seed)      = 0;
+    virtual std::vector<float> randn(uint32_t n) = 0;
+};
+
+class STDDefaultRNG : public RNG {
+private:
+    std::default_random_engine generator;
+
+public:
+    void manual_seed(uint64_t seed) {
+        generator.seed((unsigned int)seed);
+    }
+
+    std::vector<float> randn(uint32_t n) {
+        std::vector<float> result;
+        float mean   = 0.0;
+        float stddev = 1.0;
+        std::normal_distribution<float> distribution(mean, stddev);
+        for (uint32_t i = 0; i < n; i++) {
+            float random_number = distribution(generator);
+            result.push_back(random_number);
+        }
+        return result;
+    }
+};
+
+#endif  // __RNG_H__