Data commit

Task/Leap-year/Ada/leap-year.ada

@@ -0,0 +1,35 @@
+-- Incomplete code, just a sniplet to do the task. Can be used in any package or method.
+-- Adjust the type of Year if you use a different one.
+function Is_Leap_Year (Year : Integer) return Boolean is
+begin
+   if Year rem 100 = 0 then
+      return Year rem 400 = 0;
+   else
+      return Year rem 4 = 0;
+   end if;
+end Is_Leap_Year;
+
+
+-- An enhanced, more efficient version:
+-- This version only does the 2 bit comparison (rem 4) if false.
+-- It then checks rem 16 (a 4 bit comparison), and only if those are not
+-- conclusive, calls rem 100, which is the most expensive operation.
+-- I failed to be convinced of the accuracy of the algorithm at first,
+-- so I rephrased it below.
+-- FYI: 400 is evenly divisible by 16 whereas 100,200 and 300 are not. Ergo, the
+-- set of integers evenly divisible by 16 and 100 are all evenly divisible by 400.
+-- 1. If a year is not divisible by 4 => not a leap year. Skip other checks.
+-- 2. If a year is evenly divisible by 16, it is either evenly divisible by 400 or
+--    not evenly divisible by 100 => leap year. Skip further checks.
+-- 3. If a year evenly divisible by 100 => not a leap year.
+-- 4. Otherwise a leap year.
+
+function Is_Leap_Year (Year : Integer) return Boolean is
+begin
+   return (Year rem 4 = 0) and then ((Year rem 16 = 0) or else (Year rem 100 /= 0));
+end Is_Leap_Year;
+
+
+
+-- To improve speed a bit more, use with
+pragma Inline (Is_Leap_Year);