Re: [Firebird-devel] UDF Library

[Tsourinakis A. <ts...@ot...>]

On Tue, 17 Apr 2001 19:54:19 +0000 (UTC), cv...@us... ("Claudio
Valderrama C.") wrote:

>Ok, please help me to shape what you want the UDF substring should do:
>- When parameters are wrong: return NULL or empty string? Examples of wrong
>parameters: starting pos less than zero.
>- When final position is greater than the string's length, return from
>initial pos up to the last character?

I think that SUBSTR(s,n,m) must return 
 if string is NULL then 
    return NULL
else
   if aritmetic parameters are wrong 
        return EMPTY_STRING
  else
       return AS_MUCH_CHARACTERS_AS_YOU_CAN

the code you send I think is as it must be.
This is in pascal as I think that must work (I cannot catch the NULL)
======================
function Substring(s:string;m,n:integer):string;overload;
var len :integer;
begin
  len := length(s);
  if (len<1) or (m<1) or (n<1) or (m>len) then
    result:= '' //'EMPTY'
  else
    if m+n>len then
      result := copy(s,m,len-m+1)
    else
      result := copy(s,m,n)
end;

function Substring(s:string;m:integer):string;overload;
var len :integer;
begin
  len := length(s);
  if (len<1) or (m<1) or (m>len) then
    result:= '' //'EMPTY'
  else
    result := copy(s,m,len-m+1)
end;
==============
>- I understood that I should leave the current function's arguments as they
>are: starting pos, final pos. Do I create a second UDF to handle the
>pascal-style function, with starting pos and length of the slice as
>arguments?
>
I think that is also a very good idea and name it SUBSTRING (as is
more standard, see my previous answer).
I don't know if it can be used with either 2 or 3 parameters. If I
remember in C you can do such things)

Antonis Tsourinakis
Piraeus-Greece