Program Lab3;

Uses CRT;

Function Choose(Text : String; a, b : Real) : Real;
    Var
    S : String;
    Code : Integer;
    V : Real;
        X, Y : Byte;
    Begin
       Write(Text);
       X := WhereX;
       Y := WhereY;
       repeat
           GoToXY(X,Y);
           ClrEoL;
           Readln(S);
                   Val(S, V, Code);
       until (Code = 0) and (V > a) and (V < b);
    Choose := V;
    end;

Function F(x : Real) : Real;
    begin
       f := ln(1 + x);
    end;

Function Deg(n : Word; a: Real) : Real;
    begin
       if n <> 0 then
            Deg := a * Deg(n - 1, a)
       else
            Deg := 1;
    end;

Function Width(eps : Real) : Integer;
    var
       i, w : Integer;
    begin
       i := 1;
       w := 0;
       repeat
          i := i * 10;
          Inc(w);
       until ( Trunc(1 / eps) div i = 0 );
       Width := w;
    end;

Function Bsum(x, e : Real; k : Integer) : Real;
    var
       i, j : Integer;
       ak : Real;
    begin
       i := -1;
       for j := 2 to k do
           i := (-1) * i;
       ak := i * Deg(k, x) / ( k * (k - 1) );
       if (ak < e) then
        Bsum := ak + Bsum(x, e, k + 1)
       else
          Bsum := ak;
    end;

Var
  Sn, rn : Real;
  e, x : Real;
Begin
  Repeat
    ClrScr;
    TextColor(yellow);
    GoToXY(35,1);
    Writeln('"""Program"""');
    TextColor(white);
    x := Choose(' - vvedite x(-1<x<2) : ', -1, 2);
    e := Choose(' - vvedite eps(0<eps<0.5) : ', 0, 0.5);
    Sn := (Bsum(x, 0.001, 2) + x) / (1 + x);
    Writeln(' - Sn = ', Sn : 4: Width(e) );
    rn := abs( f(x) - Sn );
    Writeln(' - rn(x) = ', rn : 4: Width(e) );
    TextColor(yellow);
    Writeln('Prodolzim?(dlya vihoda nazmite klavishu Q)');
  Until ReadKey in ['Q','q'];
  Write('Goodbay...');
  Readln;
  Clrscr;
End.