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(* calculate fibonacci numbers recursively *) let fib = let rec fib_sub = fun {n; a; b} -> if n <= 1 then a else fib_sub {n=n - 1; a=a + b; b=a} in fun n -> fib_sub {n; a=1; b=1}; (* matching on variant types *) let area = fun shape -> match shape with | `Circle {rad} -> rad *. rad *. 3.1415926 | `Rect {length; height} -> length *. height; print "area `Circle {rad=5.0} =", area `Circle {rad=5.0}; print "area `Rect {height=4.; length=2.5} =", area `Rect {height=4.; length=2.5}; (* wildcard match delegates to first area function for the non-Circle cases in a type safe manner *) let area = fun shape -> match shape with | `Square {len} -> len *. len | v -> area v; print "area `Square {len=4.} =", area `Square {len=4.}; print "area `Rect {height=4.; length=2.5} =", area `Rect {height=4.; length=2.5}; print "area `Circle {rad=1.2} =", area `Circle {rad=1.2}; (* ints are arbitrary precision *) (* 999th fibonacci number = 43466557686937456435688527675040625802564660517371780402481729089536555417949051890403879840079255169295922593080322634775209689623239873322471161642996440906533187938298969649928516003704476137795166849228875 *) print "fib 999 =", fib 999;
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