计算字符串中数值的问题!!!!(50分)

我现在需要计算一字符串中的数值
如 s:string;
s:='1+2*3';
我需要得出s中的计算结果 i:=7;
请各位大虾指教!!!多谢!!!!!!!!

1.使用SQL语句代替计算:简单(等一下给你),前提是SQL要认识
2.使用自己写的函数计算:麻烦

简单的计算没有问题:
//需要去掉表达式中的逗号，小数点属于数字部分
function TForm4.DefineCalculate(Source:String):TStringList;
var S,ST:String;
i:Integer;
LB:Boolean;
SL:TStringList;
begin
SL:=TStringList.Create;
S:='';
LB:=True;//默认当前属于数字部分
for i:=1 to Length(Source) do begin
ST:=Source;
if Pos(ST,'0123456789.')=0 then begin
if LB then begin
if S<>'' then SL.Add(S);
S:=ST;LB:=False;
end else begin
S:=S+ST;
end;
end else begin
if LB then begin
S:=S+ST;
end else begin
if S<>'' then SL.Add(S);
S:=ST;LB:=True;
end;
end;
end;
if S<>'' then SL.Add(S);
Result:=SL;
end;
procedure TForm4.Button6Click(Sender: TObject);
var S,SQL:String;
i:Integer;
SL:TStringList;
begin
SL:=DefineCalculate('1+2*3');
if SL.Count=0 then exit;
SQL:='Select ';
for i:=0 to SL.Count-1 do begin
SQL:=SQL+SL;
end;
SQL:=SQL+' As CalResult';
exeSQL(ADOQuery1,SQL);//这是一个我自己的执行SQL语句的函数,你需要修改
S:=ADOQuery1.FieldByName('CalResult').AsString;
showmessage(S);
end;

user comobj;

function expression(const srule:string):
var
sc : OleVariant;
begin
sc := CreateOleObject('MSScriptControl.ScriptControl.1');
sc.Language :='JavaScript';
result:=VarToStr(sc.Eval(srule));
end;
...
s:='1+2*3';
i:=expression(s);

这时一个简单的脚本解释程序，虽然是简单脚本解释，但也慢复杂的，我做这个用了1周才实现 任意的四则混合运算。
都给你吧 ，功能比你想要的多，我一个控件的一个属性
(语法错误时 GetBaseValue 返回 －2147483640)
：支持＋ － × ÷ 四则混合运算，支持多级括号，支持相连运算10&20 --->1020
还支持以下函数
DayOfTheYear ：今年第几天
DayOfTheMonth ：本月第几天
DayOfTheWeek ：本周第几天
MonthOfTheYear ：今年第几月
WeekOfTheYear ：今年第几周
WeekOfTheMonth ：本月第几周
HourOfTheYear ：今年第几小时
HourOfTheMonth ：本月第几小时
HourOfTheWeek ：本周第几小时
HourOfTheDay ：本日第几小时
MinuteOfTheYear ：本年第几分钟
MinuteOfTheMonth：本月第分钟
MinuteOfTheWeek ：本周第几分钟
MinuteOfTheDay ：本日第几分钟
MinuteOfTheHour ：本小时第几分钟


function GetdispartChar(str:string;disPartset:chset;Var ch:char;var PartSt:string):integer;
var
i,j,len,dispos:integer;
ArrayChar:array of char;
begin
len:=0;
//---初始化分隔符－－－－－－－
for i:=0 to 255 do
if char(i) in disPartSet then
begin
inc(len);
setlength(ArrayChar,len);
ArrayChar[len-1]:=char(i);
end;
//-------找出第一个分隔符所在位置－－－－－
dispos:=2147483647;
for i:=0 to len-1 do
begin
j:=pos(ArrayChar,str);
if (J<>0) and (j<dispos) then
begin
dispos:=j;
ch:=ArrayChar;
end;
end;//end for i:=0 to len-1
if dispos=1 then PartSt:=''
else PartSt:=copy(str,1,dispos-1);
result:=dispos;
end;

function TBskyADODataSet.GetSubBaseValue(SBst:string):integer;
var
st:string;
begin
st:=sBst;
delallSpace(st);
//DelEndSpace(st);
// DelFirstSpace(st);
if st='' then result:=0
else if SearchErrorChar(st,['0'..'9'])=0 then
begin
result:=strtoint(st);
end
else if UpperCase(st)=UpperCase('DayOfTheYear') then
result:=DayOfTheYear(Now())
else if UpperCase(st)=UpperCase('DayOfTheMonth') then
result:=DayOfTheMonth(Now())
else if UpperCase(st)=UpperCase('DayOfTheWeek') then
result:=DayOfTheWeek(Now())
else if UpperCase(st)=UpperCase('MonthOfTheYear') then
result:=MonthOfTheYear(Now())
else if UpperCase(st)=UpperCase('WeekOfTheYear') then
result:=WeekOfTheYear(Now())
else if UpperCase(st)=UpperCase('WeekOfTheMonth') then
result:=WeekOfTheMonth(Now())
else if UpperCase(st)=UpperCase('HourOfTheYear') then
result:=HourOfTheYear(Now())
else if UpperCase(st)=UpperCase('HourOfTheMonth') then
result:=HourOfTheMonth(Now())
else if UpperCase(st)=UpperCase('HourOfTheWeek') then
result:=HourOfTheWeek(Now())
else if UpperCase(st)=UpperCase('HourOfTheDay') then
result:=HourOfTheDay(Now())
else if UpperCase(st)=UpperCase('MinuteOfTheYear') then
result:=MinuteOfTheYear(Now())
else if UpperCase(st)=UpperCase('MinuteOfTheMonth') then
result:=MinuteOfTheMonth(Now())
else if UpperCase(st)=UpperCase('MinuteOfTheWeek') then
result:=HourOfTheDay(Now())
else if UpperCase(st)=UpperCase('MinuteOfTheDay') then
result:=MinuteOfTheDay(Now())
else if UpperCase(st)=UpperCase('MinuteOfTheHour') then
result:=MinuteOfTheHour(Now())
else result:=-2147483640;
end;
function TBskyADODataSet.GetBaseValue(var Bst:string; pre:boolean):integer;
var
SdisChar:set of char;
preChar,dischar,MPrechar:char;
i,Int_haver,nownum,tempInt:integer;
partST:string;
ifDIgui:boolean;
begin
SdisChar:=['+','-','*','/','&','(',')'];
Int_haver:=0;
nownum:=0;
preChar:='b';
MPrechar:='s';
ifDIgui:=false;
DelENDChar(bst,'+');
Bst:=bst+'+';
if (pos('+-',Bst)<>0)
or (pos('++',Bst)<>0)
or (pos('+&',Bst)<>0)
or (pos('+*',Bst)<>0)
or (pos('+/',Bst)<>0)
or (pos('-+',Bst)<>0)
or (pos('--',Bst)<>0)
or (pos('-*',Bst)<>0)
or (pos('-/',Bst)<>0)
or (pos('-&',Bst)<>0)
or (pos('*+',Bst)<>0)
or (pos('*-',Bst)<>0)
or (pos('**',Bst)<>0)
or (pos('*/',Bst)<>0)
or (pos('*&',Bst)<>0)
or (pos('/+',Bst)<>0)
or (pos('/-',Bst)<>0)
or (pos('/*',Bst)<>0)
or (pos('//',Bst)<>0)
or (pos('/&',Bst)<>0)
or (pos('&+',Bst)<>0)
or (pos('&-',Bst)<>0)
or (pos('&*',Bst)<>0)
or (pos('&/',Bst)<>0)
or (pos('&&',Bst)<>0)
or (pos('(+',Bst)<>0)
or (pos('(-',Bst)<>0)
or (pos('(*',Bst)<>0)
or (pos('(/',Bst)<>0)
or (pos('(&',Bst)<>0)
or (pos('+)',Bst)<>0)
or (pos('-)',Bst)<>0)
or (pos('*)',Bst)<>0)
or (pos('/)',Bst)<>0)
or (pos('&)',Bst)<>0)
then
begin
result:=-2147483640;
exit;
end;

// dischar:='';
i:=GetdispartChar(Bst,Sdischar,dischar,partSt);
while i<>2147483647 do //有分隔符就一直运算
begin
System.Delete(Bst,1,i);
if (dischar='(') and (partSt<>'') then
begin
result:=-2147483640;
exit;
end;
//----------- + - * /------------
if dischar in ['+','-','&',')'] then
begin
tempInt:=GetSubBaseValue(partSt);
if tempInt=-2147483640 then
begin
result:=-2147483640;
exit;
end;
case mpreChar of
's': begin
if partSt='' then
begin
result:=-2147483640;
exit;
end;
nownum:=tempInt;
end;
'*': begin
nownum:=nownum*tempInt;
end;
'/':begin
if tempInt=0 then
begin
messagedlg('表达式除数为零！',mtError,[mbOK],0);
result:=-2147483640;
exit;
end;
nownum:=round(nownum/tempInt);
end;
end;//end case mpreChar
case preChar of
'b': begin
if (partSt='') then
begin
result:=-2147483640;
exit;
end;
Int_haver:=nownum;
end ;//'b'
'+': begin
Int_haver:=Int_haver+nownum;
end;
'-': begin
Int_haver:=Int_haver-nownum;
end;
'&': begin
Int_haver:=strtoint(inttostr(Int_haver)+inttostr(nownum));
end;
end;//end case
preChar:=dischar;
MpreChar:='s';
nownum:=0;
if (dischar=')') and pre then //递归返回
begin
result:=Int_haver;
exit;
end
else if (dischar=')') and (not pre) then
begin
result:=-2147483640;
exit;
end; //end 递归返回
end // if dischar in ['+','-','&']
else if dischar in ['*','/','('] then
begin
if dischar='(' then
begin
// pre:=true;
tempInt:=GetBaseValue(Bst,true);
if tempInt=-2147483640 then
begin
result:=-2147483640;
exit;
end;
ifDIgui:=true;
end
else
begin
tempInt:=GetSubBaseValue(partSt);
if tempInt=-2147483640 then
begin
result:=-2147483640;
exit;
end;
end;
case MpreChar of
's': begin
nownum:=tempInt;
end;
'*':begin
nownum:=nownum*tempInt;
end ;
'/':begin
if tempInt=0 then
begin
messagedlg('表达式除数为零！',mtError,[mbOK],0);
result:=-2147483640;
exit;
end;
nownum:=round(nownum/tempInt);
end;
end;//end case
if dischar<>'(' then MpreChar:=dischar;
end;// if dischar in ['*','/','(']
if ifDIgui then
begin
i:=GetdispartChar(Bst,Sdischar,dischar,partSt);
System.Delete(Bst,1,i);
if (partSt<>'') or (dischar='(')then
begin
result:=-2147483640;
exit;
end;
if dischar in ['*','/'] then MpreChar:=dischar
else
begin
case preChar of
'b': begin
//if (partSt='') then
// begin
// result:=-2147483640;
// exit;
// end;
Int_haver:=nownum;
end ;//'b'
'+': begin
Int_haver:=Int_haver+nownum;
end;
'-': begin
Int_haver:=Int_haver-nownum;
end;
'&': begin
Int_haver:=strtoint(inttostr(Int_haver)+inttostr(nownum));
end;
end;//end case
if (dischar=')') and pre then //递归返回
begin
result:=Int_haver;
exit;
end
else if (dischar=')') and (not pre) then
begin
result:=-2147483640;
exit;
end; //end 递归返回
preChar:=dischar;
MpreChar:='s';
nownum:=0;
end;//['+','-','&']
ifDIgui:=false;
end; //end ifDIgui
i:=GetdispartChar(Bst,Sdischar,dischar,partSt);
end; //end while
result:=Int_haver;
end;

对了上面的函数得到的都是整数，那是因为这是给我的TbskyADOSet 的baseValue用的，这个属性是自动产生 表的编号类字段值用的，比如一年中第几天作为 每天的基础编号xxx 然当天产生的记录编号在此基础上递增。

感谢各位的大力支持,我的问题已经搞定,多谢了!![][]

多人接受答案了。