diff --git a/code/info2/nonlin.cpp b/code/info2/nonlin.cpp
index 8be71742c..bfdf6ba1f 100644
--- a/code/info2/nonlin.cpp
+++ b/code/info2/nonlin.cpp
@@ -1,25 +1,42 @@
-#ifndef __NONLIN_H__
-#define __NONLIN_H__
-
-//  rozwiazuje rownanie   pf(x)=0 metoda bisekcji
-//  a,b to granice przedzialu, w ktorym poszukuje sie pierwiastka
-//  UWAGA: musi byc spelniony warunek:
-//  pf(a)*pf(b) <= 0 (jesli nie jest spelniony zwracana jest wartosc 0, liczba iteracji wynosi -1)
-//  jesli warunek jest spelniony
-//    wartosc zwracana = liczba iteracji uzytych dla znalezienia pierwiastka
-//    x  = poszukiwany pierwiastek okreslony z dokladnoscia "eps"
-
-//  solves equation pf(x) = 0 using bisection method
-//  a,b are the limits of the range in which the root is sought
-//  (*pf)(double) is pointer to function of type double with a one argument
-//  eps is accuracy used to stop an iteration process (eg. eps=1.e-3)
-//  *i_iter pointer to a variable storing the number of iterations
-//  WARNING: 
-//  IF condition pf(a)*pf(b) <= 0 is satisfied the function returns 
-//  the root approximation and the number of iteraions *i_iter for given eps 
-//  ELSE
-//  it returns 0, and the number of iterations is set to -1
-//
-double bisec( double a, double b, double (*pf)(double), double eps, int *i_iter);
-
-#endif // __NONLIN_H__
+#include <math.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+double bisec( double xa, double xb, double (*pf)(double), double eps, int *i_iter )
+{
+	int	i;
+	double fa, fb, xc, fc;
+
+	fa = pf(xa);
+	fb = pf(xb);
+
+	if ( fa * fb > 0.0)
+	{
+		*i_iter = -1; 
+		return 0;
+	}
+
+	for ( i = 1; i <= 1000; i++ )
+	{
+		xc = ( xa + xb ) / 2.;
+		fc = pf( xc );
+
+		if( fa * fc < 0. )
+		{
+			xb = xc;
+			fb = fc;
+		}
+		else
+		{
+			xa = xc;
+			fa = fc;
+		}
+
+		if ( fabs(fc) < eps && fabs(xb-xa) < eps)
+			break;
+	}
+
+	*i_iter = i;
+	return xc;
+}
+
diff --git a/code/info2/nonlin.h b/code/info2/nonlin.h
index 467420427..bd8fde148 100644
--- a/code/info2/nonlin.h
+++ b/code/info2/nonlin.h
@@ -8,6 +8,18 @@
 //  jesli warunek jest spelniony
 //    wartosc zwracana = liczba iteracji uzytych dla znalezienia pierwiastka
 //    x  = poszukiwany pierwiastek okreslony z dokladnoscia "eps"
+
+//  solves equation pf(x) = 0 using bisection method
+//  a,b are the limits of the range in which the root is sought
+//  (*pf)(double) is pointer to function of type double with a one argument
+//  eps is accuracy used to stop an iteration process (eg. eps=1.e-3)
+//  *i_iter pointer to a variable storing the number of iterations
+//  WARNING: 
+//  IF condition pf(a)*pf(b) <= 0 is satisfied the function returns 
+//  the root approximation and the number of iteraions *i_iter for given eps 
+//  ELSE
+//  it returns 0, and the number of iterations is set to -1
+//
 double bisec( double a, double b, double (*pf)(double), double eps, int *i_iter);
 
-#endif __NONLIN_H__
\ No newline at end of file
+#endif __NONLIN_H__