June 2018 Update

Task/Executable-library/Julia/executable-library.julia

@@ -0,0 +1,53 @@
+############### in file hailstone.jl ###############
+module Hailstone
+
+function hailstone(n)
+    ret = [n]
+    while n > 1
+        if n & 1 > 0
+            n = 3n + 1
+        else
+            n = Int(n//2)
+        end
+        append!(ret, n)
+    end
+    return ret
+end
+
+export hailstone
+
+end
+
+if PROGRAM_FILE == "hailstone.jl"
+    using Hailstone
+    h = hailstone(27)
+    n = length(h)
+    println("The sequence of hailstone(27) is:\n $h.\nThis sequence is of length $n. It starts with $(h[1:4]) and ends with $(h[n-3:end]).")
+end
+############ in file moduletest.jl ####################
+include("hailstone.jl")
+using Hailstone
+function countstones(mi, mx)
+    lengths2occurences = Dict()
+    mostfreq = mi
+    maxcount = 1
+    for i in mi:mx
+        h = hailstone(i)
+        n = length(h)
+        if haskey(lengths2occurences, n)
+            newoccurences = lengths2occurences[n] + 1
+            if newoccurences > maxcount
+                maxcount = newoccurences
+                mostfreq = n
+            end
+            lengths2occurences[n] = newoccurences
+        else
+            lengths2occurences[n] = 1
+        end
+    end
+    mostfreq, maxcount
+end
+
+nlen, cnt = countstones(1,99999)
+
+print("The most common hailstone sequence length for hailstone(n) for 1 <= n < 100000 is $nlen, which occurs $cnt times.")