Add a missing file that defines the `Unit` type.

src/structs/unit.rs

@@ -0,0 +1,78 @@
+use traits::geometry::Norm;
+
+
+/// A wrapper that ensures the undelying algebraic entity has a unit norm.
+#[repr(C)]
+#[derive(Eq, PartialEq, RustcEncodable, RustcDecodable, Clone, Hash, Debug, Copy)]
+pub struct Unit<T> {
+    v: T
+}
+
+impl<T: Norm> Unit<T> {
+    /// Normalize the given value and return it wrapped on a `Unit` structure.
+    #[inline]
+    pub fn new(v: &T) -> Self {
+        Unit { v: v.normalize() }
+    }
+
+    /// Attempts to normalize the given value and return it wrapped on a `Unit` structure.
+    ///
+    /// Returns `None` if the norm was smaller or equal to `min_norm`.
+    #[inline]
+    pub fn try_new(v: &T, min_norm: T::NormType) -> Option<Self> {
+        v.try_normalize(min_norm).map(|v| Unit { v: v })
+    }
+
+    /// Normalize the given value and return it wrapped on a `Unit` structure and its norm.
+    #[inline]
+    pub fn new_and_get(mut v: T) -> (Self, T::NormType) {
+        let n = v.normalize_mut();
+
+        (Unit { v: v }, n)
+    }
+
+    /// Normalize the given value and return it wrapped on a `Unit` structure and its norm.
+    ///
+    /// Returns `None` if the norm was smaller or equal to `min_norm`.
+    #[inline]
+    pub fn try_new_and_get(mut v: T, min_norm: T::NormType) -> Option<(Self, T::NormType)> {
+        if let Some(n) = v.try_normalize_mut(min_norm) {
+            Some((Unit { v: v }, n))
+        }
+        else {
+            None
+        }
+    }
+
+    /// Normalizes this value again. This is useful when repeated computations 
+    /// might cause a drift in the norm because of float inaccuracies.
+    ///
+    /// Returns the norm beform re-normalization (should be close to `1.0`).
+    #[inline]
+    pub fn renormalize(&mut self) -> T::NormType {
+        self.v.normalize_mut()
+    }
+}
+
+impl<T> Unit<T> {
+    /// Wraps the given value, assuming it is already normalized.
+    ///
+    /// This function is not safe because `v` is not verified to be actually normalized.
+    #[inline]
+    pub fn from_unit_value_unchecked(v: T) -> Self {
+        Unit { v: v }
+    }
+
+    /// Retrieves the underlying value.
+    #[inline]
+    pub fn unwrap(self) -> T {
+        self.v
+    }
+}
+
+impl<T> AsRef<T> for Unit<T> {
+    #[inline]
+    fn as_ref(&self) -> &T {
+        &self.v
+    }
+}