[math] Adding sigmoid and softmax functions

src/logistic.h

@@ -0,0 +1,14 @@
+#ifndef LOGISTIC_H
+#define LOGISTIC_H
+
+#include <stdlib.h>
+#include <stdint.h>
+
+#include "matrix.h"
+
+double sigmoid(double x);
+void sigmoid_vector(double *x, size_t n);
+void softmax_vector(double *x, size_t n);
+void softmax_matrix(matrix_t *matrix);
+
+#endif