I recently had to implement version string comparison for InnoSetup, because the solutions that I found on the internet did not suit my needs. Hopefully this will be useful for somebody else.

// Procedure to split a string into an array of integers procedure Explode(var Dest: TArrayOfInteger; Text: String; Separator: String); var i, p: Integer; begin i := 0; repeat SetArrayLength(Dest, i+1); p := Pos(Separator,Text); if p > 0 then begin Dest[i] := StrToInt(Copy(Text, 1, p-1)); Text := Copy(Text, p + Length(Separator), Length(Text)); i := i + 1; end else begin Dest[i] := StrToInt(Text); Text := ''; end; until Length(Text)=0; end; // Function compares version strings numerically: // * when v1 = v2, result = 0 // * when v1 < v2, result = -1 // * when v1 > v2, result = 1 // // Supports version numbers with trailing zeroes, for example 1.02.05. // Supports comparison of two version number of different lengths, for example // CompareVersions('1.2', '2.0.3') // When any of the parameters is '' (empty string) it considers version number as 0 function CompareVersions(v1: String; v2: String): Integer; var v1parts: TArrayOfInteger; v2parts: TArrayOfInteger; i: Integer; begin if v1 = '' then begin v1 := '0'; end; if v2 = '' then begin v2 := '0'; end; Explode(v1parts, v1, '.'); Explode(v2parts, v2, '.'); if (GetArrayLength(v1parts) > GetArrayLength(v2parts)) then begin SetArrayLength(v2parts, GetArrayLength(v1parts)) end else if (GetArrayLength(v2parts) > GetArrayLength(v1parts)) then begin SetArrayLength(v1parts, GetArrayLength(v2parts)) end; for i := 0 to GetArrayLength(v1parts) - 1 do begin if v1parts[i] > v2parts[i] then begin { v1 is greater } Result := 1; exit; end else if v1parts[i] < v2parts[i] then begin { v2 is greater } Result := -1; exit; end; end; { Are Equal } Result := 0; end;

To test the code in InnoSetup, you can use the following function:

procedure TestVersions(v1: String; v2: String); begin Log(v1 + ' : ' + v2 + ' = ' + IntToStr(CompareVersions(v1, v2))); end;

And call it with some parameters:

TestVersions('1', '2'); TestVersions('2', '1'); TestVersions('3', '3'); TestVersions('1.1', '1'); TestVersions('2.1', '1'); TestVersions('1.1', '2'); TestVersions('2.12.11', '2.12.25'); TestVersions('', '2.12.25'); TestVersions('2.12.25', ''); TestVersions('', ''); TestVersions('2.12.11', '2.012.11');

A practical example can be used as follows:

if CompareVersion(currentVersion, newVersion) = -1 then begin //do the upgrade end