将字符型转换成int64的函数怎么写? 用

Question

将字符型转换成int64的函数怎么写?    var
      s:int64; begin  s:=strtointdef('2121001001'); end;
  运行出错呀

Answer 1

var
  a:Integer;
begin
  a:=StrToInt64('2121001001');
end;

Answer 2

s := strtoint64def('2121001001',0);

Answer 3

var
  a:Int64;
begin
  a:=StrToInt64('2121001001');
end;

Answer 4

   var
      s:int64;//s:string; begin  s:=strtointdef('2121001001');//strtoint64(''); end;