diff --git a/include/cglm-quat.h b/include/cglm-quat.h
new file mode 100644
index 0000000..6e79a2f
--- /dev/null
+++ b/include/cglm-quat.h
@@ -0,0 +1,69 @@
+/*
+ * Copyright (c), Recep Aslantas.
+ *
+ * MIT License (MIT), http://opensource.org/licenses/MIT
+ * Full license can be found in the LICENSE file
+ */
+
+#ifndef cglm_quat_h
+#define cglm_quat_h
+
+#include "cglm.h"
+#include <math.h>
+
+CGLM_INLINE
+float
+glm_quat_dot(versor q, versor r) {
+  return q[0] * r[0] + q[1] * r[1] + q[2] * r[2] + q[3] * r[3];
+}
+
+CGLM_INLINE
+void
+glm_quat_slerp(versor q,
+               versor r,
+               float  t,
+               versor dest) {
+  float cosTheta, sinTheta, angle, a, b;
+
+  cosTheta = glm_quat_dot(q, r);
+  if (cosTheta < 0.0f) {
+    q[0] *= -1.0f;
+    q[1] *= -1.0f;
+    q[2] *= -1.0f;
+    q[3] *= -1.0f;
+
+    cosTheta = glm_quat_dot(q, r);
+  }
+
+  if (fabs(cosTheta) >= 1.0f) {
+    dest[0] = q[0];
+    dest[1] = q[1];
+    dest[2] = q[2];
+    dest[3] = q[3];
+
+    return;
+  }
+
+  sinTheta = sqrt(1.0f - cosTheta * cosTheta);
+
+  /* LERP */
+  if (fabs(sinTheta) < 0.001f) {
+    dest[0] = (1.0f - t) * q[0] + t * r[0];
+    dest[1] = (1.0f - t) * q[1] + t * r[1];
+    dest[2] = (1.0f - t) * q[2] + t * r[2];
+    dest[3] = (1.0f - t) * q[3] + t * r[3];
+    return;
+  }
+
+  /* SLERP */
+  angle = acos(cosTheta);
+  a = sin((1.0f - t) * angle) / sinTheta;
+  b = sin(t * angle) / sinTheta;
+
+  dest[0] = q[0] * a + r[0] * b;
+  dest[1] = q[1] * a + r[1] * b;
+  dest[2] = q[2] * a + r[2] * b;
+  dest[3] = q[3] * a + r[3] * b;
+}
+
+#endif /* cglm_quat_h */
diff --git a/include/cglm.h b/include/cglm.h
index f0733f9..a7ddf41 100644
--- a/include/cglm.h
+++ b/include/cglm.h
@@ -16,11 +16,7 @@ typedef float vec4[4];
 typedef vec3 mat3[3];
 typedef vec4 mat4[4];
 
-CGLM_INLINE
-void
-glm_mat_mul4(mat4 m1,
-             mat4 m2,
-             mat4 dest);
+typedef vec4 versor;
 
 #include "cglm-vec.h"
 #include "cglm-mat.h"