Re: [Caml-list] Map module

[Alessandro Baretta <alex@baretta.com>]

Brian Hurt wrote:
> On Thu, 5 Jun 2003, Alessandro Baretta wrote:
> 
> 
> Glancing at the code, it appears to be a height-balanced tree.  So 
> operations should use only O(log N) stack frames- call it something less 
> than 32 stack frames for 80K elements.  Which means either there is a bug 
> in that code, or your insert routine is not tail-recursive.
> 

The insert routine is actually tail recursive, but somewhere 
else there is something which is not tail recursive. I have 
now tried converting my code to simple read-parse-print tail 
recursive functional cycle and still I get a Stack overflow.

Here's the code:

let read_cap s = Scanf.sscanf s "%2s %5[0-9]%[^\r\n]%[\r\n]"
let rec output_table input_ch =
   try
     let line = input_line input_ch in
     let prov, cap = read_cap line (fun p c _ _ -> p, c) in
      Printf.printf "%s\t%s\n" cap prov;
       output_table input_ch
   with
     | End_of_file -> print_string ""
     | Scanf.Scan_failure (_) -> output_table input_ch


***

Ok, now I'm using a "while true" cycle with exceptions. This 
simply cannot overflow.

let output_table2 input_ch =
   try
     while true do
       try
	let line = input_line input_ch in
	let prov, cap = read_cap line (fun p c _ _ -> p, c)
           in Printf.printf "%s\t%s\n" cap prov
       with Scanf.Scan_failure (_) -> ()
     done
   with End_of_file -> ()

And, yes, this does work. So what is wrong with the 
recursive version?

Alex

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