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From: Patrick.Verkaik@p99.f124.n512.z2.fidonet.org (Patrick Verkaik)
Newsgroups: comp.lang.modula2
Subject: Comparing Strings...
Message-ID: <339.27238882@puddle.fidonet.org>
Date: 19 Oct 90 04:40:45 GMT
Sender: ufgate@puddle.fidonet.org (newsout1.26)
Organization: FidoNet node 2:512/124.99 - The Owl's Nest Node, Soest
Lines: 64

Hello Bernard,

In a message to All <16 Oct 90  1:06:00> Bernard wrote:

 v8> like to be able to find if a string is
 v8> equal to, less than, or greater than another string.  I tried
 v8> writing a routinue

I have seen the following (translated and slightly modified) in a book (by Jim van Keulen):

-+---------------------------------------------------------------

TYPE
     CompareType = (Smaller , Greater , Equal);

PROCEDURE CompareString (Str1 , Str2 : ARRAY OF CHAR) : CompareType;
     (* CompareString returns
      * Smaller if Str1 < Str2,
      * Equal   if Str1 = Str2,
      * Greater if Str1 > Str2 *)
VAR
     i : CARDINAL;
     LengthStr1 , LengthStr2 , LengthShortest : CARDINAL;

BEGIN
     LengthStr1 := LengthString (Str1);
     LengthStr2 := LengthString (Str2);
     IF LengthStr1 <= LengthStr2
     THEN
          LengthShortest := LengthStr1
     ELSE
          LengthShortest := LengthStr2
     END;
     FOR i := 0 TO LengthShortest DO
          IF Str1 [i] < Str2 [i]
          THEN
               RETURN Smaller
          ELSIF Str1 [i] > Str2 [i]
               RETURN Greater
          END
     END;

     (* One of either strings forms the beginning of the other *)
     IF LengthShortest < LengthStr2
     THEN
          RETURN Smaller
     ELSIF LengthShortest < LengthStr1
          RETURN Greater
     ELSE
          RETURN Equal
     END
END CompareString;

-+---------------------------------------------------------------

That's it, I've assumed you do have a procedure that returns the length of a string (LengthString or whatever yours is called) otherwise I can give you that source too, if you want it...

Hope this has helped you!

PDV

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