program NumericExtractor;
{ Enable Object Pascal mode and extended syntax }
{$mode objfpc}{$H+}
{**
* Removes all non-numeric characters from a string, returning only digits (0-9).
*
* @param inputStr The source string containing alphanumeric and special characters.
* @return A new string containing only numeric digits.
*}
function ExtractNumericOnly(const inputStr: string): string;
var
i: Integer;
len: Integer;
destIndex: Integer;
begin
len := Length(inputStr);
{ Pre-allocate the result string to the maximum possible length
to prevent performance penalties from frequent reallocations }
SetLength(Result, len);
destIndex := 1;
for i := 1 to len do
begin
{ Check if the current character is a numeric digit between '0' and '9' }
if (inputStr[i] >= '0') and (inputStr[i] <= '9') then
begin
Result[destIndex] := inputStr[i];
Inc(destIndex);
end;
end;
{ Trim the result string down to the exact number of digits found }
SetLength(Result, destIndex - 1);
end;
{ --- Main Program Demonstration --- }
var
originalText: string;
cleanedText: string;
begin
originalText := '123XYZ +9982-programming 10000000000001language';
cleanedText := ExtractNumericOnly(originalText);
Writeln('Original: ', originalText);
Writeln('Cleaned: ', cleanedText);
end.
(*
run:
Original: 123XYZ +9982-programming 10000000000001language
Cleaned: 123998210000000000001
*)
