let rec(@)j s=Printf.printf"On the %s day of Christmas, my true love sent to me %sA%s partridge in a pear tree%c "[|"twelfth";"eleventh";"tenth";"ninth";"eighth";"seventh";"sixth";"fifth";"fourth";"third";"second";"first"|].(j)s[|"nd a";""|].(j/11)"!.".[min 1j];j-1@([|"Twelve drummers drumming";"Eleven pipers piping";"Ten lords a-leaping";"Nine ladies dancing";"Eight maids a-milking";"Seven swans a-swimming";"Six geese a-laying";"Five golden rings";"Four calling birds";"Three French hens";"Two turtle doves"|].(j-1)^", "^s);;11@""
Note that non-ascii characters in the above source code will be escaped (such as \x9f).