[m-rev.] for review: make parsing tail recursive

[Zoltan Somogyi]

On 07-May-2008, Paul Bone <pbone at csse.unimelb.edu.au> wrote:
>     ( Token = io_error(IO_Error) ->
>         io.error_message(IO_Error, IO_ErrorMessage),
>         string.append("I/O error: ", IO_ErrorMessage, Message)
>     ; Token = junk(Char) -> 
>         char.to_int(Char, Code), 
>         string.int_to_base_string(Code, 10, Decimal),
>         string.int_to_base_string(Code, 16, Hex),
>         string.append_list(["Syntax error: Illegal character 0x", Hex,
>             " (", Decimal, ") in input"], Message)
>     ; Token = error(ErrorMessage) ->
>         string.append("Syntax error: ", ErrorMessage, Message)
>     ;
>         check_for_bad_token(Tokens, Message, LineNum)
>                                              ^^^^^^^ It's unified here too,
>         when LineNum is unified here it probably shouldn't be unified against
>         the line number in the first argument.
>     ).  
> 
> Perhaps using a switch over all the function symbols that Token may be can help as well.

Yes, that would be a good idea. The reason why didn't do it originally
is that it would have required duplicating the code for the "everything else"
case, but that has not been a concern since I implemented multi-cons-id
switch arms.

Zoltan.
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