Extract numbers from a string with Delphi

type

  TCharSet = set of Char;

function StripNonConforming(const S: string;

  const ValidChars: TCharSet): string;

var

  DestI: Integer;

  SourceI: Integer;

begin

  SetLength(Result, Length(S));

  DestI := 0;

  for SourceI := 1 to Length(S) do

    if S[SourceI] in

      ValidChars then

    begin

      Inc(DestI);

      Result[DestI] := S[SourceI]

    end;

  SetLength(Result,

    DestI)

end;

function StripNonNumeric(const S: string): string;

begin

  Result :=

    StripNonConforming(S, ['0'..'9'])

end;