ocaml: phase 5.1 polygon_area.ml baseline (pentagon 2x area = 32)

Shoelace formula on a pentagon with integer vertices:

  pts = [(0,0); (4,0); (4,3); (2,5); (0,3)]

  2 * area = | Σ (x_i * y_{i+1} - x_{i+1} * y_i) |
           = | 0*0 - 4*0 + 4*3 - 4*0 + 4*5 - 2*3 + 2*3 - 0*5
                + 0*0 - 0*3 |
           = 32

Returns the doubled form (32) to stay integral.

Tests:
  - let (x1, y1) = arr.(i) in   -- tuple destructure from array
  - arr.((i + 1) mod n)         -- modular wrap-around index
  - if a < 0 then - a else a    -- prefix - negation

162 baseline programs total.

lib/ocaml/baseline/expected.json

@@ -122,6 +122,7 @@
   "prefix_sum.ml": 66,
   "pretty_table.ml": 64,
   "poly_stack.ml": 5,
+  "polygon_area.ml": 32,
   "pow_mod.ml": 738639,
   "prime_factors.ml": 17,
   "pythagorean.ml": 16,