[optimization] moving regularization methods to their own module

src/regularization.h

@@ -0,0 +1,15 @@
+#ifndef REGULARIZATION_H
+#define REGULARIZATION_H
+
+#include <stdlib.h>
+
+typedef enum {
+    REGULARIZATION_NONE,
+    REGULARIZATION_L1,
+    REGULARIZATION_L2
+} regularization_type_t;
+
+void regularize_l2(double *theta, size_t n, double reg_update);
+void regularize_l1(double *theta, size_t n, double reg_update);
+
+#endif