l2 norm

src/linalg/mod.rs

+mod vector;
\ No newline at end of file

src/linalg/vector.rs

+pub struct Vector<'a> {
+    _repr: &'a [f32],
+}
+
+impl<'a> Vector<'a> {
+    pub fn len(&self) -> usize {
+        self._repr.len()
+    }
+
+    pub fn l2_sim(&self, other: &Vector<'a>) -> f32 {
+        debug_assert!(self.len() == other.len());
+
+        self._repr
+            .iter()
+            .zip(other._repr)
+            .map(|(x, y)| {
+                let diff = x - y;
+                diff * diff
+            })
+            .sum::<f32>()
+            .sqrt()
+    }
+}
+
+impl<'a> From<&'a [f32]> for Vector<'a> {
+    fn from(value: &'a [f32]) -> Self {
+        Vector { _repr: value }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const TOLERANCE: f32 = 1e-8;
+
+    fn close(actual: f32, target: f32) -> bool {
+        (target - actual).abs() < TOLERANCE
+    }
+
+    fn unsuspicious_l2(suspect: f32) -> bool {
+        suspect.is_finite() && suspect >= 0.0
+    }
+
+    #[test]
+    fn self_sim_is_zero() {
+        let testvec = Vector::from([1.0, 2.0, 3.0, 1.5].as_slice());
+        let selfsim = testvec.l2_sim(&testvec);
+        assert!(unsuspicious_l2(selfsim));
+        assert!(close(selfsim, 0.0));
+    }
+}

src/main.rs

+mod linalg;
+
 fn main() {
     println!("Hello, world!");
+    
 }