Module Lwtreslib.Traced

Traced is a functor to generate advanced combined-monad replacements for parts of the Stdlib. The generated module is similar to Bare with the addition of traces: structured collections of errors.

For convenience, the monad includes primitives to error directly with a trace rather than a bare error.

All the _ep traversors return traces of errors rather than lists of errors. The _ep traversors preserve their best-effort semantic.

Additional functions in the Monad allow the construction of sequential traces: functions to enrich traces with new errors. E.g.,

let load_config file =
   Result.map_error
     (fun trace ->
        Trace.cons "cannot load configuration file" trace)
   @@ begin
     let open Lwt_result_syntax in
     let* file = open_file in
     let* lines = read_lines file in
     let* json = parse_config lines in
     make_dictionary json
   end

Example implementations of traces are provided in the traces/ directory.