clock: passes tests, iteration 1 (?)

cpp/clock/clock.cpp

@@ -0,0 +1,71 @@
+#include "clock.h"
+
+#include <cstring>
+
+namespace date_independent {
+
+namespace {
+
+const minutes_t minutes_per_hour = 60;
+const hours_t   hours_per_day    = 24;
+const total_t   minutes_per_day  = hours_per_day * minutes_per_hour;
+
+inline void make_date_independent(total_t total_minutes)
+{
+    while (total_minutes < 0)
+        total_minutes += minutes_per_day;
+
+    total_minutes = total_minutes % minutes_per_day;
+}
+
+}
+
+
+clock::clock(hours_t hours, minutes_t minutes)
+{
+    total_minutes_ = minutes_per_hour*hours + minutes;
+    make_date_independent(total_minutes_);
+}
+
+bool clock::operator==(const clock &other) const
+{
+    return total_minutes_ == other.total_minutes_;
+}
+
+bool clock::operator!=(const clock &other) const
+{
+    return !(*this == other);
+}
+
+clock clock::at(hours_t hours, minutes_t minutes)
+{
+    return clock(hours, minutes);
+}
+
+clock clock::plus(minutes_t minutes) const
+{
+    clock result(*this);
+
+    result.total_minutes_ += minutes;
+    make_date_independent(result.total_minutes_);
+
+    return result;
+}
+
+clock clock::minus(minutes_t minutes) const
+{
+    return plus(-minutes);
+}
+
+clock::operator std::string() const
+{
+    minutes_t minutes = total_minutes_ % minutes_per_hour
+    hours_t   hours   = total_minutes_ / minutes_per_hour;
+
+    char buff[6];
+    snprintf(buff, 6, "%.2i:%.2i", hours, minutes);
+
+    return buff;
+}
+
+}