diff --git a/histogram.cpp b/histogram.cpp
index 6744741..41fad77 100644
--- a/histogram.cpp
+++ b/histogram.cpp
@@ -1,7 +1,7 @@
 #include "histogram.h"
 #include <vector>
 
-static void find_minmax(const std::vector <double> &numbers, double &min, double &max){
+void find_minmax(const std::vector <double> &numbers, double &min, double &max){
     min = numbers[0];
     max = numbers[0];
     for ( double x : numbers ){
@@ -13,15 +13,15 @@ static void find_minmax(const std::vector <double> &numbers, double &min, double
     }
 }
 
-std::vector<std::size_t> make_histogram(const std::vector<double> &numbers, size_t bin_count) {
+std::vector<std::size_t> make_histogram(const std::vector<double> &numbers, std::size_t bin_count) {
     double min = numbers[0];
     double max = numbers[0];
     find_minmax(numbers, min, max);
     double bin_size = ( max - min ) / bin_count;
     std::vector<std::size_t> bins ( bin_count );
-    for (size_t i=0; i <  numbers.size(); i++ ){
+    for (std::size_t i=0; i <  numbers.size(); i++ ){
         bool found = false;
-        for (size_t j = 0; ( j < bin_count - 1 ) && !found; j++ ){
+        for (std::size_t j = 0; ( j < bin_count - 1 ) && !found; j++ ){
             auto lo = min + j * bin_size;
             auto hi = min + ( j + 1 ) * bin_size;
             if (lo <= numbers[i] && ( numbers[i] < hi )){