old/PAS/STRINGANALYZE/MAS2.PAS

const
 deyst: set of char = ['+','-','*','/','(',')','^'];
var
  i1,i2,i3,i4 : byte;
  a : string;
  ret : longint;

function calc(var sum : longint; num:longint;dey:char) : boolean;
var i : byte;
    res : longint;
begin
  case dey of
       '^': begin
              if num = 0 then sum:=1;
              res:=sum;
              for i := 2 to num do sum:=res*sum;
            end;
       '+': sum := sum + num;
       '-': sum := sum - num;
       '*': sum := sum * num;
       '/': if num <> 0 then sum := sum div num
            else
         Begin
           calc := false;
           exit;
          End;
  end;
  calc := true;
end;

function Findnum(a:string;pos,dir:byte):longint;
var
  ret   :longint;
  st    :string;
  code  :integer;
begin
 st:='';
 if dir = 1 then inc(pos) else dec(pos);
  if dir = 1 then
   while (not (a[pos] in deyst))and(pos<>length(a)+1) do
    begin
      st := st + a[pos];
      inc(pos);
    end
  else
   while (not (a[pos] in deyst)) and (pos<>0) do
    begin
      insert(a[pos],st,1);
      dec(pos);
    end;
 if (pos=1)and(a[pos]='-') then insert(a[pos],st,1);
 if st[1] = '.' then st[1] :='-';
 Val(st,ret,code);
 FindNum:=ret;
end;{FindNum}

Procedure Ends(st:string);
begin
  Writeln(st);
  Halt(3);
end;

Function Calculate(a:string):string;
var
  res       : longint;
  j,i       : byte;
  code      : integer;
  ch        : byte;
  num1,num2 : longint;
  tmp1,tmp2 : string;
  min       : boolean;
begin
  if a[1] = '-' then a[1] := '.';
  while pos(' ',a) <> 0 do delete(a,pos(' ',a),1);

  if (pos('(',a)<>0) or (pos(')',a)<>0) then
   begin
     j:=pos('(',a);
     if j = 0 then Ends('Ошибка в скобках');
     i := 1;
     ch := j+1;
     while i <> 0 do
      begin
       if a[ch] = '(' then inc(i);
       if a[ch] = ')' then dec(i);
       inc(ch);
      end;
     tmp1:=copy(a,j+1,ch-j-2);
     tmp1:=calculate(tmp1);
     delete(a,j,ch-j);
     insert(tmp1,a,j);
   end;

  while (pos('^',a)<>0) do
    begin
      i := pos('^',a);
      num1 := findnum(a,i,0);
      str(num1,tmp1);
      num2 := findnum(a,i,1);
      str(num2,tmp2);
      calc(num1,num2,a[i]);
      delete(a,i-length(tmp1),length(tmp1)+1+length(tmp2));
      str(num1,tmp2);
      insert(tmp2,a,i-length(tmp1))
    end;

  while (pos('*',a)<>0)or(pos('/',a)<>0) do
    begin
      i := pos('*',a);
      j := pos('/',a);
      if ((i<j) or (j=0)) and (i<>0) then
       begin
         num1 := findnum(a,i,0);
         str(num1,tmp1);
         num2 := findnum(a,i,1);
         str(num2,tmp2);
         calc(num1,num2,a[i]);
         delete(a,i-length(tmp1),length(tmp1)+1+length(tmp2));
         str(num1,tmp2);
         if tmp2[1] = '-' then tmp2[1]:='.';
         insert(tmp2,a,i-length(tmp1))
       end
      else
       begin
         num1 := findnum(a,j,0);
         str(num1,tmp1);
         num2 := findnum(a,j,1);
         str(num2,tmp2);
         calc(num1,num2,a[j]);
         delete(a,j-length(tmp1),length(tmp1)+1+length(tmp2));
         str(num1,tmp2);
         if tmp2[1] = '-' then tmp2[1]:='.';
         insert(tmp2,a,j-length(tmp1))
       end;
    end;

  min:=true;

  while ((pos('+',a)<>0)or(pos('-',a)<>0)) and min do
  begin
      i := pos('+',a);
      j := pos('-',a);
      if ((i<j) or (j=0)) and (i<>0) then
       begin
         num1 := findnum(a,i,0);
         str(num1,tmp1);
         num2 := findnum(a,i,1);
         str(num2,tmp2);
         calc(num1,num2,a[i]);
         delete(a,i-length(tmp1),length(tmp1)+1+length(tmp2));
         str(num1,tmp2);
         if tmp2[1] = '-' then tmp2[1]:='.';
         insert(tmp2,a,i-length(tmp1))
       end
      else
       begin
         num1 := findnum(a,j,0);
         str(num1,tmp1);
         num2 := findnum(a,j,1);
         str(num2,tmp2);
         calc(num1,num2,a[j]);
         delete(a,j-length(tmp1),length(tmp1)+1+length(tmp2));
         str(num1,tmp2);
         if tmp2[1] = '-' then tmp2[1]:='.';
         insert(tmp2,a,j-length(tmp1))
       end;
  end;
  calculate:=a;
end;

Function Simply(a:string):longint;
var
 res:longint;
 code:integer;
begin
 a:=Calculate(a);
 if a[1] = '.' then a[1] :='-';
 val(a,res,code);
 Simply:=res;
end;

begin
  WriteLN('Введите пример:  ');
  ReadLn(a);
  WriteLn(Simply(a));
  readln
end.