Re: Reprise: 'in out' parameters for functions

["Alexander E. Kopilovich" <aek@VB1162.spb.edu>]

Stephen Leake wrote:

> I just ran across a need for an 'in out' parameter in a function, in
> "real code", so I thought I post it here "just for fun" :).
>
> This is what I wanted to declare:
>
> function Parse
>   (Error_Label : in     String;
>    Token       : in out Token_List.List_Iterator)
>   return String;
>   --  Process Token, which should contain '([Config_File =>] <string>)'.
>   --  Return the string.
>   --  Delete parsed tokens from Token.
>
> Token must be 'in out', because the next parse function called wants
> to work on the stuff after the config file.
>
> Parse must be a function, because I'm returning a String.
>
> The work-around is to use a procedure and a bounded string:
>
>    procedure Parse
>      (Error_Label      : in     String;
>       Token            : in out Token_List.List_Iterator;
>       Config_File_Name :    out OpenToken.Buffers.Bounded_String);
>
> In this instance, the body of Parse deals with
> OpenToken.Buffers.Bounded_String anyway, so there's no actual new
> overhead introduced. But the user interface is not as clean as it
> could be.

One thing is missing in this your explanation: why exactly you don't want to
make that List_Iterator global (instead of passing it as IN OUT argument) ?



Alexander Kopilovitch                      aek@vib.usr.pu.ru
Saint-Petersburg
Russia