Considering the sample code below that contains non-functional stuff
that mimics a simple XmlScanner from my company.
type event = StartElement | EndElement | Text | EndOfDocument
let cur_name = ref None
let name () = match !cur_name with None -> failwith "None" | Some name
-> name
let next it =
match !it with
| [] -> failwith "Unexpected end of source"
| hd :: tl -> it := tl; cur_name := Some (snd hd); fst hd
let read_section_while source test f a =
let rec handle_next a =
match next source, name () with
| EndOfDocument, _ -> failwith "Unexpected end of document"
| Text, _ -> handle_next (f a "Text")
| StartElement, "titi" -> handle_next (f a "Start titi")
| EndElement, "tata" -> handle_next (f a "End tata")
| xml -> if test xml then handle_next
a else a
in
handle_next a
let source = [
(StartElement, "toto");
(StartElement, "titi");
(EndElement, "titi");
(StartElement, "tata");
(EndElement, "tata");
(EndElement, "toto");
(EndOfDocument, "dummy")
];;
read_section_while (ref source) ((<>) (EndElement, "toto")) (fun a x -
> x :: a) [];;
==== END SAMPLE ===
I have an exception "Unexpected end of source" while the code was
supposed to stop normally on (EndElement, "toto")
The same code works as expected if I just change slightly the default
pattern:
| ev, name -> if test (ev, name) then handle_next a else a
instead of:
| xml -> if test xml then handle_next a else a
Again, the same code works if I make the tuple resulting from (next
it, name ()) just before the pattern matching:
let x = next source, name () in match next x with
instead of:
match next source, name () with
>From my point of view, I thought that there was no fundamental
difference between the code that works and the code that fails. Maybe
I missed something...
I am using Ocaml 3.11.0 and I don't plan to update for the moment
since I am experiencing 3rd party library link problems as soon as
something change in the Ocaml+MinGW+Cygwin+FlexDLL toolchain.
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