diff -r aa6129697116 -r d7cd14b8ccc0 src/newton.rs
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/newton.rs	Wed Dec 04 23:19:46 2024 -0500
@@ -0,0 +1,34 @@
+/*!
+Newton method in 2D.
+*/
+
+use alg_tools::types::*;
+
+#[inline]
+pub fn newton_sym1x1<F : Float>(
+    g : impl Fn(F) -> (F, F),
+    mut x : F,
+    iters : usize
+) -> F {
+    for _i in 0..iters {
+        let (a, b) = g(x);
+        x -= b / a
+    }
+    x
+}
+
+#[inline]
+pub fn newton_sym2x2<F : Float>(
+    g : impl Fn(F, F) -> ([F; 3], [F; 2]),
+    [mut x1, mut x2] : [F; 2],
+    iters : usize
+) -> [F; 2] {
+    for _i in 0..iters {
+        let ([a11, a12, a22], [b1, b2]) = g(x1, x2);
+        let q = a11 * a22 - a12 * a12;
+        x1 -= (a22 * b1 - a12 * b2) / q;
+        x2 -= (a11 * b2 - a12 * b1) / q;
+    }
+    [x1, x2]
+}
+