ocaml: phase 5.1 euler3.ml baseline (largest prime factor of 13195 = 29)

PE3's worked example. Trial-division streaming: when the current
factor divides m, divide and update largest; otherwise bump factor:

  let largest_prime_factor n =
    let m = ref n in
    let factor = ref 2 in
    let largest = ref 0 in
    while !m > 1 do
      if !m mod !factor = 0 then begin
        largest := !factor;
        m := !m / !factor
      end else factor := !factor + 1
    done;
    !largest

  largest_prime_factor 13195 = 29  (= 5 * 7 * 13 * 29)

The full PE3 number 600851475143 exceeds JS safe-int (2^53 ≈ 9e15
in float terms; 6e11 is fine but the intermediate 'i mod !factor'
on the way to 6857 can overflow precision). 13195 keeps the program
portable across hosts.

113 baseline programs total.

lib/ocaml/baseline/euler3.ml

@@ -0,0 +1,15 @@
+let largest_prime_factor n =
+  let m = ref n in
+  let factor = ref 2 in
+  let largest = ref 0 in
+  while !m > 1 do
+    if !m mod !factor = 0 then begin
+      largest := !factor;
+      m := !m / !factor
+    end else factor := !factor + 1
+  done;
+  !largest
+
+;;
+
+largest_prime_factor 13195

lib/ocaml/baseline/expected.json

@@ -28,6 +28,7 @@
   "euler1.ml": 233168,
   "euler10.ml": 1060,
   "euler2.ml": 4613732,
+  "euler3.ml": 29,
   "euler4_small.ml": 9009,
   "euler5.ml": 232792560,
   "euler6.ml": 25164150,