Re: Getting the current line number

John Reppy wrote:

> After thinking about it a bit more, I realized that the following hack
> would work.  First, define the following helper function
> 
> fun file_line ex = let
>       val [s] = SMLofNJ.exnHistory ex
>       val (f, r) = Substring.splitl (fn #":" => false | _ => true) 
> (Substring.full s)
>       val ln = Substring.takel (fn #"." => false | _ => true) 
> (Substring.triml 1 r)
>       in
>         {file = Substring.string f, line = Substring.string ln}
>       end;
> 
> then you can get the file and line info at a given source code location
> by embedding the following code:
> 
> file_line ((raise Fail "") handle ex => ex);

	It just occurred to me, for the future reference of others, that you 
could probably actually make this is a little lighter as

exception Info

fun file_info (exthunk : unit -> string list) = let
        val [s] = (exthunk () handle ex => SMLofNJ.exnHistory ex)
        val (f, r) = Substring.splitl (fn #":" => false | _ => true) 
(Substring.full s)
        val ln = Substring.takel (fn #"." => false | _ => true) 
(Substring.triml 1 r)
        in
          {file = Substring.string f, line = Substring.string ln}
        end

val a = file_info (fn _ => raise Info)

val b = file_info (fn _ => raise Info)

Which actually isn't too bad, especially if body of the function using 
the information is a mostly a let expression already.  I don't see any 
way to do better without a preprocessor, an extension to SML/NJ, or 
another esoteric SML/NJ internals feature.



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