diff --git a/matrix/SquareMatrix.hpp b/matrix/SquareMatrix.hpp
index dbcb307..3063051 100644
--- a/matrix/SquareMatrix.hpp
+++ b/matrix/SquareMatrix.hpp
@@ -66,8 +66,8 @@ class SquareMatrix : public Matrix<Type, M, M>
         return res;
     }
 
-    // get matrix upper right triangle
-    Vector<Type, M * (M + 1) / 2> urt() const
+    // get matrix upper right triangle in a row-major vector format
+    Vector<Type, M * (M + 1) / 2> upper_right_triangle() const
     {
         Vector<Type, M * (M + 1) / 2> res;
         const SquareMatrix<Type, M> &self = *this;
@@ -149,7 +149,7 @@ bool inv(const SquareMatrix<Type, M> & A, SquareMatrix<Type, M> & inv)
     for (size_t n = 0; n < M; n++) {
 
         // if diagonal is zero, swap with row below
-        if (fabs(static_cast<float>(U(n, n))) < __FLT_EPSILON__) {
+        if (fabs(static_cast<float>(U(n, n))) < FLT_EPSILON) {
             //printf("trying pivot for row %d\n",n);
             for (size_t i = n + 1; i < M; i++) {
 
@@ -174,7 +174,7 @@ bool inv(const SquareMatrix<Type, M> & A, SquareMatrix<Type, M> & inv)
 #endif
 
         // failsafe, return zero matrix
-        if (fabs(static_cast<float>(U(n, n))) < __FLT_EPSILON__) {
+        if (fabs(static_cast<float>(U(n, n))) < FLT_EPSILON) {
             return false;
         }
 
diff --git a/matrix/stdlib_imports.hpp b/matrix/stdlib_imports.hpp
index 1f6b88b..6e98a0d 100644
--- a/matrix/stdlib_imports.hpp
+++ b/matrix/stdlib_imports.hpp
@@ -15,6 +15,10 @@
 
 namespace matrix {
 
+#if !defined(FLT_EPSILON)
+#define FLT_EPSILON     __FLT_EPSILON__
+#endif
+
 #if defined(__PX4_NUTTX)
 /*
  * NuttX has no usable C++ math library, so we need to provide the needed definitions here manually.
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 2453f70..0dc8480 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -18,7 +18,7 @@ set(tests
     hatvee
     copyto
     least_squares
-    urt
+    upperRightTriangle
     )
 
 add_custom_target(test_build)
diff --git a/test/helper.cpp b/test/helper.cpp
index dda3c90..a21c90a 100644
--- a/test/helper.cpp
+++ b/test/helper.cpp
@@ -5,15 +5,15 @@ using namespace matrix;
 
 int main()
 {
-    TEST(fabs(wrap_pi(4.0) - (4.0 - 2*M_PI)) < __FLT_EPSILON__);
-    TEST(fabs(wrap_pi(-4.0) - (-4.0 + 2*M_PI)) < __FLT_EPSILON__);
-    TEST(fabs(wrap_pi(3.0) - (3.0)) < __FLT_EPSILON__);
+    TEST(fabs(wrap_pi(4.0) - (4.0 - 2*M_PI)) < FLT_EPSILON);
+    TEST(fabs(wrap_pi(-4.0) - (-4.0 + 2*M_PI)) < FLT_EPSILON);
+    TEST(fabs(wrap_pi(3.0) - (3.0)) < FLT_EPSILON);
     TEST(!is_finite(wrap_pi(1000.0f)));
     TEST(!is_finite(wrap_pi(-1000.0f)));
     wrap_pi(NAN);
 
-    TEST(fabs(wrap_2pi(-4.0) - (-4.0 + 2*M_PI)) < __FLT_EPSILON__);
-    TEST(fabs(wrap_2pi(3.0) - (3.0)) < __FLT_EPSILON__);
+    TEST(fabs(wrap_2pi(-4.0) - (-4.0 + 2*M_PI)) < FLT_EPSILON);
+    TEST(fabs(wrap_2pi(3.0) - (3.0)) < FLT_EPSILON);
     TEST(!is_finite(wrap_2pi(1000.0f)));
     TEST(!is_finite(wrap_2pi(-1000.0f)));
     wrap_2pi(NAN);
diff --git a/test/matrixAssignment.cpp b/test/matrixAssignment.cpp
index 81e3412..994af85 100644
--- a/test/matrixAssignment.cpp
+++ b/test/matrixAssignment.cpp
@@ -22,7 +22,7 @@ int main()
     Matrix3f m2(data);
 
     for(int i=0; i<9; i++) {
-        TEST(fabs(data[i] - m2.data()[i]) < __FLT_EPSILON__);
+        TEST(fabs(data[i] - m2.data()[i]) < FLT_EPSILON);
     }
 
     Matrix3f m_nan;
@@ -38,7 +38,7 @@ int main()
     };
     m2 = Matrix3f(data2d);
     for(int i=0; i<9; i++) {
-        TEST(fabs(data[i] - m2.data()[i]) < __FLT_EPSILON__);
+        TEST(fabs(data[i] - m2.data()[i]) < FLT_EPSILON);
     }
 
     float data_times_2[9] = {2, 4, 6, 8, 10, 12, 14, 16, 18};
@@ -100,16 +100,16 @@ int main()
     m4.swapCols(2, 2);
     TEST(isEqual(m4, Matrix3f(data)));
 
-    TEST(fabs(m4.min() - 1) < __FLT_EPSILON__);
-    TEST(fabs((-m4).min() + 9) < __FLT_EPSILON__);
+    TEST(fabs(m4.min() - 1) < FLT_EPSILON);
+    TEST(fabs((-m4).min() + 9) < FLT_EPSILON);
 
     Scalar<float> s = 1;
     const Vector<float, 1> & s_vect = s;
-    TEST(fabs(s - 1) < __FLT_EPSILON__);
-    TEST(fabs(s_vect(0) - 1.0f) < __FLT_EPSILON__);
+    TEST(fabs(s - 1) < FLT_EPSILON);
+    TEST(fabs(s_vect(0) - 1.0f) < FLT_EPSILON);
 
     Matrix<float, 1, 1> m5 = s;
-    TEST(fabs(m5(0,0) - s) < __FLT_EPSILON__);
+    TEST(fabs(m5(0,0) - s) < FLT_EPSILON);
 
     Matrix<float, 2, 2> m6;
     m6.setRow(0, Vector2f(1, 2));
diff --git a/test/setIdentity.cpp b/test/setIdentity.cpp
index fd96791..289e286 100644
--- a/test/setIdentity.cpp
+++ b/test/setIdentity.cpp
@@ -11,10 +11,10 @@ int main()
     for (size_t i = 0; i < 3; i++) {
         for (size_t j = 0; j < 3; j++) {
             if (i == j) {
-                TEST(fabs(A(i, j) -  1) < __FLT_EPSILON__);
+                TEST(fabs(A(i, j) -  1) < FLT_EPSILON);
 
             } else {
-                TEST(fabs(A(i, j) -  0) < __FLT_EPSILON__);
+                TEST(fabs(A(i, j) -  0) < FLT_EPSILON);
             }
         }
     }
@@ -25,10 +25,10 @@ int main()
     for (size_t i = 0; i < 3; i++) {
         for (size_t j = 0; j < 3; j++) {
             if (i == j) {
-                TEST(fabs(B(i, j) -  1) < __FLT_EPSILON__);
+                TEST(fabs(B(i, j) -  1) < FLT_EPSILON);
 
             } else {
-                TEST(fabs(B(i, j) -  0) < __FLT_EPSILON__);
+                TEST(fabs(B(i, j) -  0) < FLT_EPSILON);
             }
         }
     }
diff --git a/test/squareMatrix.cpp b/test/squareMatrix.cpp
index 1fc4bed..861139e 100644
--- a/test/squareMatrix.cpp
+++ b/test/squareMatrix.cpp
@@ -14,7 +14,7 @@ int main()
     Vector3<float> diag_check(1, 5, 10);
 
     TEST(isEqual(A.diag(), diag_check));
-    TEST(A.trace() - 16 < __FLT_EPSILON__);
+    TEST(A.trace() - 16 < FLT_EPSILON);
 
     float data_check[9] = {
         1.01158503f,  0.02190432f,  0.03238144f,
diff --git a/test/test_data.py b/test/test_data.py
index 85fa79c..61ef1d0 100644
--- a/test/test_data.py
+++ b/test/test_data.py
@@ -75,9 +75,9 @@ def quat_to_dcm(q):
 print('euler', phi, theta, psi)
 
 q = euler_to_quat(phi, theta, psi)
-assert(abs(norm(q) - 1) < __FLT_EPSILON__)
-assert(abs(norm(q) - 1) < __FLT_EPSILON__)
-assert(norm(array(quat_to_euler(q)) - array([phi, theta, psi])) < __FLT_EPSILON__)
+assert(abs(norm(q) - 1) < FLT_EPSILON)
+assert(abs(norm(q) - 1) < FLT_EPSILON)
+assert(norm(array(quat_to_euler(q)) - array([phi, theta, psi])) < FLT_EPSILON)
 print('\nq:')
 pprint(q)
 
@@ -85,8 +85,8 @@ def quat_to_dcm(q):
 assert(norm(dcm[:,0]) == 1)
 assert(norm(dcm[:,1]) == 1)
 assert(norm(dcm[:,2]) == 1)
-assert(abs(dcm[:,0].dot(dcm[:,1])) < __FLT_EPSILON__)
-assert(abs(dcm[:,0].dot(dcm[:,2])) < __FLT_EPSILON__)
+assert(abs(dcm[:,0].dot(dcm[:,1])) < FLT_EPSILON)
+assert(abs(dcm[:,0].dot(dcm[:,2])) < FLT_EPSILON)
 print('\ndcm:')
 pprint(dcm)
 
diff --git a/test/test_macros.hpp b/test/test_macros.hpp
index f21c5a6..d6ca2d2 100644
--- a/test/test_macros.hpp
+++ b/test/test_macros.hpp
@@ -10,7 +10,6 @@
 
 #include <cstdio>
 #include <cmath>    // cmath has to be introduced BEFORE we poison the C library identifiers
-#include "float.h"
 
 #define TEST(X) if(!(X)) { fprintf(stderr, "test failed on %s:%d\n", __FILE__, __LINE__); return -1;}
 
diff --git a/test/urt.cpp b/test/upperRightTriangle.cpp
similarity index 83%
rename from test/urt.cpp
rename to test/upperRightTriangle.cpp
index 7b54d05..9807365 100644
--- a/test/urt.cpp
+++ b/test/upperRightTriangle.cpp
@@ -14,7 +14,7 @@ int main()
     SquareMatrix<float, 3> A(data);
 
     for(int i=0; i<6; i++) {
-        TEST(fabs(urt[i] - A.urt().data()[i]) < __FLT_EPSILON__);
+        TEST(fabs(urt[i] - A.upper_right_triangle().data()[i]) < FLT_EPSILON);
     }
 
     return 0;
diff --git a/test/vector2.cpp b/test/vector2.cpp
index d5bf782..1ea88fc 100644
--- a/test/vector2.cpp
+++ b/test/vector2.cpp
@@ -10,29 +10,29 @@ int main()
 {
     Vector2f a(1, 0);
     Vector2f b(0, 1);
-    TEST(fabs(a % b - 1.0f) < __FLT_EPSILON__);
+    TEST(fabs(a % b - 1.0f) < FLT_EPSILON);
 
     Vector2f c;
-    TEST(fabs(c(0) - 0) < __FLT_EPSILON__);
-    TEST(fabs(c(1) - 0) < __FLT_EPSILON__);
+    TEST(fabs(c(0) - 0) < FLT_EPSILON);
+    TEST(fabs(c(1) - 0) < FLT_EPSILON);
 
     Matrix<float, 2, 1> d(a);
-    TEST(fabs(d(0,0) - 1) < __FLT_EPSILON__);
-    TEST(fabs(d(1,0) - 0) < __FLT_EPSILON__);
+    TEST(fabs(d(0,0) - 1) < FLT_EPSILON);
+    TEST(fabs(d(1,0) - 0) < FLT_EPSILON);
 
     Vector2f e(d);
-    TEST(fabs(e(0) - 1) < __FLT_EPSILON__);
-    TEST(fabs(e(1) - 0) < __FLT_EPSILON__);
+    TEST(fabs(e(0) - 1) < FLT_EPSILON);
+    TEST(fabs(e(1) - 0) < FLT_EPSILON);
 
     float data[] = {4,5};
     Vector2f f(data);
-    TEST(fabs(f(0) - 4) < __FLT_EPSILON__);
-    TEST(fabs(f(1) - 5) < __FLT_EPSILON__);
+    TEST(fabs(f(0) - 4) < FLT_EPSILON);
+    TEST(fabs(f(1) - 5) < FLT_EPSILON);
 
     Vector3f g(1.23f, 423.4f, 3221.f);
     Vector2f h(g);
-    TEST(fabs(h(0) - 1.23f) < __FLT_EPSILON__);
-    TEST(fabs(h(1) - 423.4f) < __FLT_EPSILON__);
+    TEST(fabs(h(0) - 1.23f) < FLT_EPSILON);
+    TEST(fabs(h(1) - 423.4f) < FLT_EPSILON);
 
     return 0;
 }