diff --git a/Projekt2_Knuettel_Daniel.c b/Projekt2_Knuettel_Daniel.c
index d546d44..f443415 100644
--- a/Projekt2_Knuettel_Daniel.c
+++ b/Projekt2_Knuettel_Daniel.c
@@ -50,6 +50,15 @@
  *
  * gcc -o main -lm Projekt2_Knuettel_Daniel.c lib/lrmp.c lib/vorrueckwaertsub.c
  *
+ *
+ * Preprocessor flags:
+ *
+ * - DEBUG turns on some more output.
+ * - NOCRAPMODE enables a reusable interface which is not conformous to the
+ *   specification given but allowes to used the algorithms with arbitrary
+ *   functions. Also this adds the functions `write_error_(newton|bisek)`.
+ * - ALLOW_NEGATGIVE_ERRORS allows negative errors which might be interesting.
+ *
  */
 
 
@@ -88,7 +97,8 @@ int bisec_one(double * x_minus
  * \param eps Used precision.
  * \param Nmax Stop searching after Nmax iterations.
  * \param flag Will be set to 0xf000, if the goal has been reached,
- *             to 0xf001, if Nmax has been reached.
+ *             to 0xf001, if Nmax has been reached
+ *             , to 0xf004 if f(a)*f(b) >= 0.
  *             Any other value indicates an unknown error.
  * \param file The function will not use this parameter, it is there just
  *             for backwards compability.
@@ -104,6 +114,7 @@ double bisek(double (*f)(double)
 		, int * flag
 		, FILE * file);
 
+#ifdef NOCRAPMODE
 /*
  * \brief Calculate f(x) < eps using bisek and write the results to file.
  *
@@ -113,12 +124,15 @@ double bisek(double (*f)(double)
  * \param eps Used precision.
  * \param Nmax Stop searching after Nmax iterations.
  * \param flag Will be set to 0xf000, if the goal has been reached,
- *             to 0xf001, if Nmax has been reached.
+ *             to 0xf001, if Nmax has been reached
+ *             , to 0xf004 if f(a)*f(b) >= 0.
  *             Any other value indicates an unknown error.
  * \param file Write ``Nmax,error\n`` to this file.
  * \param x0 The real result for bisek.
+ *
+ * \return The result of the bisection
  * */
-int write_error_bisek(double (*f)(double)
+double write_error_bisek(double (*f)(double)
 		, double a
 		, double b
 		, double eps
@@ -126,6 +140,7 @@ int write_error_bisek(double (*f)(double)
 		, int * flag
 		, FILE * file
 		, double x0);
+#endif
 
 
 
@@ -155,6 +170,7 @@ double newton(double x0
 		, FILE * file);
 
 
+#ifdef NOCRAPMODE
 /*
  * \brief Calculate f(x) < eps or a minimum of f. And write the results to file
  *
@@ -181,6 +197,7 @@ double write_error_newton(double x0
 		, int * flag
 		, FILE * file
 		, double x1);
+#endif
 
 /*
  * \brief Calculate one step of the newton iteration.
@@ -282,6 +299,7 @@ double dg2(double x);
 void g(double * x, double * y, int N);
 void dg(double * x, double ** y, int N);
 
+
 int main(void)
 {
 
@@ -289,41 +307,57 @@ int main(void)
 	int flag;
 	double result;
 
-//	// Calculate the bisection of g1.
-//	for(i = 1, j = 0; i < 100 ;i += 1, j++)
-//	{
-//		write_error_bisek(g1, -2.5, -100, 1e-7, i, &flag, stdout, -6);
-//	}
-//	printf("XXX\n");
-//	fprintf(stderr, "wrote %d lines for g1 to /dev/stdout\n", j);
-//	
-//	// Calculate the bisection of g2.
-//	// Note that the output of this will be basically crap, because
-//	// g2 does not meet the requirements for a bisection.
-//	for(i = 1, j = 0; i < 100 ;i += 1, j++)
-//	{
-//		write_error_bisek(g2, -2.5, -100, 1e-7, i, &flag, stdout, -6);
-//	}
-//	printf("XXX\n");
-//	fprintf(stderr, "wrote %d lines for g2 to /dev/stdout\n", j);
-//
-//	// Calculate the newton iteration of g1.
-//	for(i = 1, j = 0; i < 100 ;i += 1, j++)
-//	{
-//		write_error_newton(-100, g1, dg1, 1e-7, i, &flag, stdout, -6);
-//	}
-//	printf("XXX\n");
-//	fprintf(stderr, "wrote %d lines for g1 to /dev/stdout\n", j);
-//	
-//	// Calculate the newton iteration of g2.
-//	// Note that the output of this will be basically crap, because
-//	// g2 does not meet the requirements for the newton iteration.
-//	for(i = 1, j = 0; i < 100 ;i += 1, j++)
-//	{
-//		write_error_newton(-100, g2, dg1, 1e-7, i, &flag, stdout, -6);
-//	}
-//	printf("XXX\n");
-//	fprintf(stderr, "wrote %d lines for g2 to /dev/stdout\n", j);
+	// Calculate the bisection of g1.
+	for(i = 1, j = 0; i < 100 ;i += 1, j++)
+	{
+#ifdef NOCRAPMODE
+		write_error_bisek(g1, -2.5, -100, 1e-7, i, &flag, stdout, -6);
+#else
+		bisek(g1, -2.5, -100, 1e-7, i, &flag, stdout);
+#endif
+	}
+	printf("XXX\n");
+	fprintf(stderr, "wrote %d lines for g1 to /dev/stdout\n", j);
+	
+	// Calculate the bisection of g2.
+	// Note that the output of this will be basically crap, because
+	// g2 does not meet the requirements for a bisection.
+	for(i = 1, j = 0; i < 100 ;i += 1, j++)
+	{
+#ifdef NOCRAPMODE
+		write_error_bisek(g2, -2.5, -100, 1e-7, i, &flag, stdout, -6);
+#else
+		bisek(g2, -2.5, -100, 1e-7, i, &flag, stdout);
+#endif
+	}
+	printf("XXX\n");
+	fprintf(stderr, "wrote %d lines for g2 to /dev/stdout\n", j);
+
+	// Calculate the newton iteration of g1.
+	for(i = 1, j = 0; i < 100 ;i += 1, j++)
+	{
+#ifdef NOCRAPMODE
+		write_error_newton(-100, g1, dg1, 1e-7, i, &flag, stdout, -6);
+#else
+		newton(-100, g1, dg1, 1e-7, i, &flag, stdout);
+#endif
+	}
+	printf("XXX\n");
+	fprintf(stderr, "wrote %d lines for g1 to /dev/stdout\n", j);
+	
+	// Calculate the newton iteration of g2.
+	// Note that the output of this will be basically crap, because
+	// g2 does not meet the requirements for the newton iteration.
+	for(i = 1, j = 0; i < 100 ;i += 1, j++)
+	{
+#ifdef NOCRAPMODE
+		write_error_newton(-100, g2, dg2, 1e-7, i, &flag, stdout, -6);
+#else
+		newton(-100, g2, dg2, 1e-7, i, &flag, stdout);
+#endif
+	}
+	printf("XXX\n");
+	fprintf(stderr, "wrote %d lines for g2 to /dev/stdout\n", j);
 
 	// Calculate the multi dimensional newton iteration
 	
@@ -433,7 +467,13 @@ int bisec_one(double * x_minus
 	return 0;
 }
 
-double bisek(double (*f)(double)
+double 
+#ifdef NOCRAPMODE
+	bisek
+#else
+	__inline_bisek
+#endif
+	(double (*f)(double)
 		, double a
 		, double b
 		, double eps
@@ -441,6 +481,11 @@ double bisek(double (*f)(double)
 		, int * flag
 		, FILE * file)
 {
+	if(f(a)*f(b) >= 0)
+	{
+		*flag = 0xf004;
+		return 0;
+	}
 	double x_minus = a
 		, x_plus = b;
 	if(a > b)
@@ -466,23 +511,45 @@ double bisek(double (*f)(double)
 	return x_minus;
 }
 
-int write_error_bisek(double (*f)(double)
+double 
+#ifdef NOCRAPMODE
+	write_error_bisek
+#else
+	bisek
+#endif
+	(double (*f)(double)
 		, double a
 		, double b
 		, double eps
 		, int Nmax
 		, int * flag
 		, FILE * file
-		, double x0)
+#ifdef NOCRAPMODE
+		, double x0
+#endif
+		)
 {
+#ifndef NOCRAPMODE
+	double x0 = -6;
+#endif
 	double result
 		, error;
 
-	result = bisek(f, a, b, eps, Nmax, flag, file);
-	if(*flag & 0xff)
+	result = 
+#ifdef NOCRAPMODE
+		bisek
+#else
+		__inline_bisek
+#endif
+			(f, a, b, eps, Nmax, flag, file);
+	if(*flag & 0x0f == 0x01)
 	{
 		fprintf(stderr, "WARNING: bisek(..., eps = %.10e, Nmax = %d, ...) hit Nmax.\n", eps, Nmax);
 	}
+	if(*flag & 0x0f == 0x04)
+	{
+		fprintf(stderr, "WARNING: bisek(..., eps = %.10e, Nmax = %d, ...) conditions failed.\n", eps, Nmax);
+	}
 	if(!(*flag & 0xff00))
 	{
 		fprintf(stderr, "WARNING: bisek flag is invalid.\n");
@@ -494,12 +561,15 @@ int write_error_bisek(double (*f)(double)
 	// FIXME:
 	// Shold we allow negative errors? It is mathematically incorrect but
 	// more interesting.
-//	if(error < 0)
-//	{
-//		error *= -1;
-//	}
+#ifndef ALLOW_NEGATGIVE_ERRORS
+	if(error < 0)
+	{
+		error *= -1;
+	}
+#endif
 	
-	return fprintf(file, "%d,%.10e\n", Nmax, error);
+	fprintf(file, "%d,%.10e\n", Nmax, error);
+	return result;
 }
 
 
@@ -511,7 +581,9 @@ int newton_one(double * x
 	double y, yd;
 	y = f(*x);
 	yd = df(*x);
+#ifdef DEBUG
 	fprintf(stderr, "f(%.4e) -> %.4e; df(%.4e) -> %.4e\n", *x, y, *x, yd);
+#endif
 	if(abs(y) < eps)
 	{
 		return 0xe000;
@@ -522,12 +594,20 @@ int newton_one(double * x
 	}
 
 	*x -= y / yd;
+#ifdef DEBUG
 	fprintf(stderr, "set new x: %.4e\n", *x);
+#endif
 	return 0;
 }
 
 
-double newton(double x0
+double 
+#ifdef NOCRAPMODE
+	newton
+#else
+	__inline_newton
+#endif
+	(double x0
 		, double (*f)(double)
 		, double (*df)(double)
 		, double eps
@@ -556,18 +636,36 @@ double newton(double x0
 
 }
 
-double write_error_newton(double x0
+double 
+#ifdef NOCRAPMODE
+	write_error_newton
+#else
+	newton
+#endif
+		(double x0
 		, double (*f)(double)
 		, double (*df)(double)
 		, double eps
 		, int Nmax
 		, int * flag
 		, FILE * file
-		, double x1)
+#ifdef NOCRAPMODE
+		, double x1
+#endif
+		)
 {
+#ifndef NOCRAPMODE
+	double x1 = -6;
+#endif
 	double result, error;
 
-	result = newton(x0, f, df, eps, Nmax, flag, file);
+	result = 
+#ifdef NOCRAPMODE
+		newton
+#else
+		__inline_newton
+#endif
+			(x0, f, df, eps, Nmax, flag, file);
 
 	if(*flag & 0xff)
 	{
@@ -584,12 +682,15 @@ double write_error_newton(double x0
 	// FIXME:
 	// Shold we allow negative errors? It is mathematically incorrect but
 	// more interesting.
-//	if(error < 0)
-//	{
-//		error *= -1;
-//	}
+#ifndef ALLOW_NEGATGIVE_ERRORS
+	if(error < 0)
+	{
+		error *= -1;
+	}
+#endif
 	
-	return fprintf(file, "%d,%.10e\n", Nmax, error);
+	fprintf(file, "%d,%.10e\n", Nmax, error);
+	return result;
 }
 
 int newton_mult(int N