Fs.DirectorySourceval fold_files_rec_result :
?ext:string ->
('a -> file -> ('a, Or_error.msg) Or_error.result) ->
'a ->
t ->
('a, [> Or_error.msg ]) Or_error.resultfold_files_rec_result ~ext f acc d recursively folds f over the files with extension matching ext (defaults to "") contained in d and its sub directories. Stop as soon as f returns Error _.