Custom Stringlist Sort

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Introduction

"Dictionary" Sort Custom "Numeric" Sort
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Here's a program illustrating the use of the "Custom Sort" feature of the Delphi TStringList class. The default TStringList "Sort" method arranges the strings in lexicographic (dictionary) order. The "CustomSort" method passes two index pointers to a user defined function and expects the user function
to return one of three values: -1, +1, or 0 indicating that the first string is "less than", "greater than" or "equal to" the second string.

In this demonstration program, the requirement is to sort a set of file names containing embedded numeric information into sequence accounting for the numeric values. For example, "A100A.xxx" will come before "A11.xxx" in a standard sort but after if numbers are treated as numeric values.

The user function in this case separates each pair of strings into 3 pieces: an alpha prefix, a number, and an alpha suffix. The alphabetic parts are converted to upper case to make the comparison case insensitive. The pieces are compared in sequence with a non-equal result after each piece
determining the returned result.

 

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Created: September 8, 2013

Modified: July 29, 2017

 
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