Removed irrelevant code.

examples/angularMomentum/attitude.go

@@ -1,7 +1,6 @@
 package dynamics
 
 import (
-	"fmt"
 	"math"
 
 	"github.com/gonum/matrix/mat64"
@@ -97,10 +96,6 @@ func (s *MRP) B() *mat64.Dense {
 	return B
 }
 
-func (s *MRP) String() string {
-	return fmt.Sprintf("[%1.5f  %1.5f  %1.5f]", s.s1, s.s2, s.s3)
-}
-
 // Attitude defines an attitude with an orientation, an angular velocity and an inertial tensor.
 // *ALMOST* implements rk4.Integrable.
 type Attitude struct {

examples/angularMomentum/geometry.go

@@ -1,10 +1,6 @@
 package dynamics
 
-import (
-	"math"
-
-	"github.com/gonum/matrix/mat64"
-)
+import "math"
 
 // norm returns the norm of a given vector which is supposed to be 3x1.
 func norm(v []float64) float64 {
@@ -16,13 +12,6 @@ func dot(a, b []float64) float64 {
 	return a[0]*b[0] + a[1]*b[1] + a[2]*b[2]
 }
 
-// cross performs the inner product.
-func cross(a, b []float64) []float64 {
-	return []float64{a[1]*b[2] - a[2]*b[1],
-		a[2]*b[0] - a[0]*b[2],
-		a[0]*b[1] - a[1]*b[0]} // Cross product R x V.
-}
-
 // Spherical2Cartesian returns the provided spherical coordinates vector in Cartesian.
 func Spherical2Cartesian(a []float64) (b []float64) {
 	b = make([]float64, 3)
@@ -55,12 +44,3 @@ func Deg2rad(a float64) float64 {
 func Rad2deg(a float64) float64 {
 	return a / (2 * math.Pi) * 360.0
 }
-
-// MxV33 multiplies a matrix with a vector. Note that there is no dimension check!
-func MxV33(m *mat64.Dense, v []float64) (o []float64) {
-	o = make([]float64, 3)
-	o[0] = m.At(0, 0)*v[0] + m.At(0, 1)*v[1] + m.At(0, 2)*v[2]
-	o[1] = m.At(1, 0)*v[0] + m.At(1, 1)*v[1] + m.At(1, 2)*v[2]
-	o[2] = m.At(2, 0)*v[0] + m.At(2, 1)*v[1] + m.At(2, 2)*v[2]
-	return
-}

integrable_test.go

@@ -0,0 +1,12 @@
+package ode
+
+import "testing"
+
+func assertPanic(t *testing.T, msg string, f func()) {
+	defer func() {
+		if r := recover(); r == nil {
+			t.Errorf("code did not panic with %s", msg)
+		}
+	}()
+	f()
+}

rk4_test.go

@@ -76,3 +76,13 @@ func TestRK4Attitude(t *testing.T) {
 		t.Fatalf("angular momentum changed by %4.12f", diff)
 	}
 }
+
+func TestPanics(t *testing.T) {
+	assertPanic(t, "negative step", func() {
+		NewRK4(1, -1, nil)
+	})
+
+	assertPanic(t, "nil integrator", func() {
+		NewRK4(1, 1, nil)
+	})
+}