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This is a program to define and test a substitute for the substring search function Posex that was  not available in versions before Delphi 7.    Here is Delphi's definition:

function PosEx(const SubStr, S: string; Offset: Cardinal = 1): Integer;

PosEx returns the index of SubStr in S, beginning the search at Offset. If Offset is 1 (default), PosEx is equivalent to Pos. PosEx returns 0 if SubStr is not found, if Offset is greater than the length of S, or if Offset is less than 1.

I coded my version to this definition so logically the code is similar.   I coded a version of Pos as a base for Posex and both are included here.   The program was written several years ago when a Delphi 5 user asked for one in order to recompile one of my the programs which uses Posex.  He recently wrote again because he had mislaid the original answer and, as a result, I decided to post the program here in Delphi techniques section. 

An even more interesting part of the project was implementing compile time conditional directives to include testing against the official Posex if  the program is compiled with Delphi  7 or later.   There is a predefined constant, CompilerVersion, which is compiled into each version of Delphi.  In can be tested in code to conditionally execute sections based on its value, however this doesn't work if the code to be executed references names not defined in the current Delphi version.  The solution is to use the conditional directives to include or exclude code in the source.  For example inserting Strutils into the Uses statement for Delphi 7 or later (to access PosEx), looks like this:

uses Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
{$IF declared(CompilerVersion) and (CompilerVersion>=15.0)}
    {$define TestPosEx}
    strutils,
{$IFEND}
StdCtrls, ShellAPI;

The variable TestPosEx is defined to use as a shortcut for testing in other code sections where the included testing for Delphi version of PosEx is to be included.  Like this:

{$IFDEF TestPosEx }

  ... insert Posex test code here

{$ENDIF}
 

A table associating Delphi external numbers with CompilerVersion  and RTLVersion (Run Time Library) numbers can be found at http://blog.blong.com/p/ancient-blog-posts.html.  Here's the pertinent table extracted from that interesting article:   

Running/Exploring the Program 

Suggestions for Further Explorations

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