Now have a simple stats test.

meson.build

@@ -137,6 +137,7 @@ executable('runtests', sources + [
   'tests/rituals.cpp',
   'tests/sound.cpp',
   'tests/spatialmap.cpp',
+  'tests/stats.cpp',
   'tests/textures.cpp',
   'tests/tilemap.cpp',
   ],

rand.hpp

@@ -20,8 +20,8 @@ namespace Random {
   }
 
   template<typename T>
-  T normal(T from, T to) {
+  T normal(T mean, T stddev) {
-    std::normal_distribution<T> rand(from, to);
+    std::normal_distribution<T> rand(mean, stddev);
 
     return rand(GENERATOR);
   }

stats.hpp

@@ -7,16 +7,16 @@ struct Stats {
 
   double sum = 0.0;
   double sumsq = 0.0;
-  unsigned long n = 0L;
+  double n = 0.0;
   double min = 0.0;
   double max = 0.0;
 
   inline void reset() {
-    sum = 0;
+    sum = 0.0;
-    sumsq = 0;
+    sumsq = 0.0;
-    n = 0L;
+    n = 0.0;
-    min = 0;
+    min = 0.0;
-    max = 0;
+    max = 0.0;
   }
 
   inline double mean() {
@@ -24,8 +24,7 @@ struct Stats {
   }
 
   inline double stddev() {
-    return std::sqrt((sumsq - (sum * sum / n)) /
+    return std::sqrt((sumsq - (sum * sum / n)) / (n - 1));
-        (n - 1));
   }
 
   inline void sample(double s) {

tests/stats.cpp

@@ -0,0 +1,27 @@
+#include <catch2/catch_test_macros.hpp>
+#include "stats.hpp"
+#include "rand.hpp"
+#include <cmath>
+#include <fmt/core.h>
+
+TEST_CASE("basic stats tests", "[stats]") {
+  Stats stat1;
+  stat1.sample(1.0);
+
+  for(int i = 0; i < 20; i++) {
+    double x = Random::normal(20.0,5.0);
+    stat1.sample(x);
+    REQUIRE(!std::isnan(stat1.stddev()));
+    REQUIRE(stat1.mean() < stat1.mean() + stat1.stddev() * 4.0);
+  }
+
+  stat1.dump();
+
+  stat1.reset();
+  REQUIRE(stat1.n == 0.0);
+
+  auto timer = stat1.time_start();
+  for(int i = 0; i < 20; i++) {
+    stat1.sample_time(timer);
+  }
+}