Sounds a bit silly to write something like that by hand, when you could use BatList.drop_while (from batteries) like so: let line_is_not_header line =

Sounds a bit silly to write something like that by hand, when you could use BatList.drop_while (from batteries) like so: let line_is_not_header line = String.length line < 4 || String.sub line 0 3 != "+++" match (BatList.drop_while line_is_not_header lines) with | header_line :: following_lines -> header env header_line; modified env 0 following_lines | _ -> () In practice, I find that it's rarely useful to write recursive functions by hand, unless you're willing to limit yourself to the default stdlib.