build: test find_minmax

histogram.cpp

@@ -4,7 +4,7 @@
 
 using namespace std;
 
-static void
+void
 find_minmax(const vector<double>& numbers, double& min, double& max) {
     min = numbers[0];
     max = numbers[0];

histogram_internal.h

@@ -0,0 +1,9 @@
+#ifndef HISTOGRAM_H_INCLUDED
+#define HISTOGRAM_H_INCLUDED
+
+#include <vector>
+
+void
+find_minmax(const std::vector<double>& numbers, double& min, double& max);
+
+#endif // HISTOGRAM_H_INCLUDED