Octave / zadan6_1

function F = zadan6_1(f,a,b,e)
  if(a > b || e < 0)
    F = 'Неверные данные';
    return;
  else 
    fa = f(a);
    fb = f(b);
    if (fa * fb < 0)
      while(true)
        fa = f(a);
        fb = f(b);
        c = a - ((b - a)/(fb - fa)) * fa;
        fc = f(c);
        if (abs(fc) < e)
          break;
        else
          if(fa * fc < 0)
            b = c;
          else
            a = c;
          endif
        endif
      endwhile
    else
      F = 'Неверные данные';
      return;
    endif
  endif
  F = c;
endfunction