源代码网整理以下由于标准的数字变量类型取值有限，如果需要进行运算的数字超过了范围，用标准的数字变量类型就显得无能为力了！下面的四个函数利用Delphi中的字符串对象实现了大数运算。
源代码网整理以下加法、乘法由zswang编写
源代码网整理以下function StrLeft(const mStr: string; mDelimiter: string): string;
begin
Result := Copy(mStr, 1, Pos(mDelimiter, mStr) - 1);
end; { StrLeft }
源代码网整理以下function StrRight(const mStr: string; mDelimiter: string): string;
begin
if Pos(mDelimiter, mStr) <= 0 then
Result := ´´
else Result := Copy(mStr, Pos(mDelimiter, mStr) + Length(mDelimiter), MaxInt);
end; { StrRight }
软件开发网 www.mscto.com
源代码网整理以下function formatnum(mNumber: string):string;
var
m:integer;
TemStr:string;
begin
Result:=´´;
for m:=1 to Length(mNumber) do
begin
if mNumber[m]=´.´ then
Result:=Result+´.´
else
Result:=Result+IntToStr(StrToIntDef(mNumber[m], 0));
end;
while Pos(´0´, Result) = 1 do Delete(Result, 1, 1); //排除整数前无效的0
if Pos(´.´, Result )<= 0 then Result := Result + ´.´; //没有有小数点补小数点
TemStr:=StrRight(Result,´.´);
while Copy(TemStr, Length(TemStr), 1) = ´0´ do Delete(TemStr, Length(TemStr), 1); //排除小数后无效的0
Result:=StrLeft(Result,´.´)+´.´+TemStr;
if Copy(Result, Length(Result), 1) = ´.´ then Delete(Result, Length(Result), 1); //排除无效小数点
if Copy(Result, 1, 1)=´.´ then Result:=´0´+Result;
if (Result = ´´) then Result := ´0´;
end;
源代码网整理以下function InfiniteAdd(mNumberA, mNumberB: string): string; { 无限位数加法 }
var
I: Integer;
T: Integer;
begin
Result := ´´;
if Pos(´.´, mNumberA) <= 0 then mNumberA := mNumberA + ´.´; //没有有小数点补小数点
if Pos(´.´, mNumberB) <= 0 then mNumberB := mNumberB + ´.´; //没有有小数点补小数点
I := Max(Length(StrLeft(mNumberA, ´.´)), Length(StrLeft(mNumberB, ´.´))); //整数部分最大长度
mNumberA := DupeString(´0´, I - Length(StrLeft(mNumberA, ´.´))) + mNumberA; //整数前补0
mNumberB := DupeString(´0´, I - Length(StrLeft(mNumberB, ´.´))) + mNumberB; //整数前补0
T := Max(Length(StrRight(mNumberA, ´.´)), Length(StrRight(mNumberB, ´.´))); //小数部分最大长度
mNumberA := mNumberA + DupeString(´0´, T - Length(StrRight(mNumberA, ´.´))); //小数后补0
mNumberB := mNumberB + DupeString(´0´, T - Length(StrRight(mNumberB, ´.´))); //小数后补0
I := I + T + 1; //计算总长度//小数长度和整数长度加上小数点长度
T := 0; //进位数初始化
for I := I downto 1 do //从后向前扫描
if [mNumberA[I], mNumberB[I]] <> [´.´] then begin //不是小数点时
T := StrToIntDef(mNumberA[I], 0) + T; //累加当前数位
T := StrToIntDef(mNumberB[I], 0) + T; //累加当前数位
Result := IntToStr(T mod 10) + Result; //计算当前数位上的数字
T := T div 10; //计算进位数
end else Result := ´.´ + Result; //加上小数点
if T <> 0 then Result := IntToStr(T mod 10) + Result; //处理进位数
while Pos(´0´, Result) = 1 do Delete(Result, 1, 1); //排除整数前无效的0
while Copy(Result, Length(Result), 1) = ´0´ do
Delete(Result, Length(Result), 1); //排除小数后无效的0
if Copy(Result, Length(Result), 1) = ´.´ then
Delete(Result, Length(Result), 1); //排除无效小数点
if Copy(Result, 1, 1) = ´.´ then Result := ´0´ + Result; //处理无0小数情况
if (Result = ´´) then Result := ´0´; //处理空字符情况
end; { InfiniteAdd }
软件开发网 www.mscto.com
源代码网整理以下function InfiniteMult(mNumberA, mNumberB: string): string; { 无限位数乘法 }
源代码网整理以下 function fMult(mNumber: string; mByte: Byte): string; { 无限位数乘法子函数 }
var
I: Integer;
T: Integer;
begin
Result := ´´;
T := 0;
for I := Length(mNumber) downto 1 do begin //从后向前扫描
T := StrToIntDef(mNumber[I], 0) * mByte + T; //累加当前数位
Result := IntToStr(T mod 10) + Result; //计算当前数位上的数字
T := T div 10; //计算进位数
end;
if T <> 0 then Result := IntToStr(T mod 10) + Result; //处理进位数
end; { fMult }
源代码网整理以下var
I: Integer;
vDecimal: Integer; //小数位数
T: string;
begin
Result := ´´;
///////Begin 处理小数
if Pos(´.´, mNumberA) <= 0 then mNumberA := mNumberA + ´.´; //没有有小数点补小数点
if Pos(´.´, mNumberB) <= 0 then mNumberB := mNumberB + ´.´; //没有有小数点补小数点
vDecimal := Length(StrRight(mNumberA, ´.´)) + Length(StrRight(mNumberB, ´.´)); //计算小数位数
mNumberA := StrLeft(mNumberA, ´.´) + StrRight(mNumberA, ´.´); //删除小数点
mNumberB := StrLeft(mNumberB, ´.´) + StrRight(mNumberB, ´.´); //删除小数点
///////End 处理小数
T := ´´;
for I := Length(mNumberB) downto 1 do begin
Result := InfiniteAdd(Result, fMult(mNumberA, StrToIntDef(mNumberB[I], 0)) + T);
T := T + ´0´;
end;
Insert(´.´, Result, Length(Result) - vDecimal + 1);
while Pos(´0´, Result) = 1 do Delete(Result, 1, 1); //排除整数前无效的0
while Copy(Result, Length(Result), 1) = ´0´ do
Delete(Result, Length(Result), 1); //排除小数后无效的0
if Copy(Result, Length(Result), 1) = ´.´ then
Delete(Result, Length(Result), 1); //排除无效小数点
if Copy(Result, 1, 1) = ´.´ then Result := ´0´ + Result; //处理无0小数情况
if (Result = ´´) then Result := ´0´; //处理空字符情况
end; { InfiniteMult }
源代码网整理以下function InfiniteSub(mNumberA, mNumberB: string): string; { 无限位数减法 }
var
I: Integer;
T: Integer;
TemNumA:String;
minus:Boolean;
begin
Result := ´´;
mNumberA:=formatnum(mNumberA);
mNumberB:=formatnum(mNumberB);
if Pos(´.´, mNumberA) <= 0 then mNumberA := mNumberA + ´.´; //没有有小数点补小数点
if Pos(´.´, mNumberB) <= 0 then mNumberB := mNumberB + ´.´; //没有有小数点补小数点
I := Max(Length(StrLeft(mNumberA, ´.´)), Length(StrLeft(mNumberB, ´.´))); //整数部分最大长度
mNumberA := DupeString(´0´, I - Length(StrLeft(mNumberA, ´.´))) + mNumberA; //整数前补0
mNumberB := DupeString(´0´, I - Length(StrLeft(mNumberB, ´.´))) + mNumberB; //整数前补0
T := Max(Length(StrRight(mNumberA, ´.´)), Length(StrRight(mNumberB, ´.´))); //小数部分最大长度
if ((Length(StrLeft(mNumberA, ´.´))) > (Length(StrLeft(mNumberB, ´.´)))) or(((Length(StrLeft(mNumberA, ´.´))) = (Length(StrLeft(mNumberB, ´.´))))and(mNumberB>mNumberA))then
begin
TemNumA := mNumberA;
mNumberA := mNumberB + DupeString(´0´, T - Length(StrRight(mNumberB, ´.´))); //小数后补0
mNumberB := TemNumA + DupeString(´0´, T - Length(StrRight(TemNumA, ´.´))); //小数后补0
minus:=True;
end
else
begin
mNumberA := mNumberA + DupeString(´0´, T - Length(StrRight(mNumberA, ´.´))); //小数后补0
mNumberB := mNumberB + DupeString(´0´, T - Length(StrRight(mNumberB, ´.´))); //小数后补0
minus:=False;
end;
I := I + T + 1; //计算总长度//小数长度和整数长度加上小数点长度
T := 0; //进位数初始化
for I := I downto 1 do //从后向前扫描
if [mNumberA[I], mNumberB[I]] <> [´.´] then begin //不是小数点时
T := StrToIntDef(mNumberB[I], 0) - T; //累加当前数位
T := StrToIntDef(mNumberA[I], 0) - T; //累加当前数位
if (T<0) and (I<>1) then
begin
T:=T+10;
Result := IntToStr(T mod 10) + Result; //计算当前数位上的数字
T := -1; //计算进位数
end
else
begin
Result := IntToStr(T mod 10) + Result; //计算当前数位上的数字
T := T div 10; //计算进位数
