From 7903a4611830b252b87b23e367374b6939bd1ec2 Mon Sep 17 00:00:00 2001
From: Glen Whitney <glen@studioinfinity.org>
Date: Thu, 24 Apr 2025 20:52:43 -0700
Subject: [PATCH] feat: add cis and fix indistinguishable

---
 src/complex/__test__/type.spec.js | 4 ++++
 src/complex/relational.js         | 4 ++--
 src/complex/type.js               | 5 ++++-
 3 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/src/complex/__test__/type.spec.js b/src/complex/__test__/type.spec.js
index b85797f..6ea0875 100644
--- a/src/complex/__test__/type.spec.js
+++ b/src/complex/__test__/type.spec.js
@@ -32,4 +32,8 @@ describe('complex type operations', () => {
       assert(!assoc(b, cplx(false, true)))
       assert(!assoc(cplx(0, 1), b))
    })
+   it('computes cis of an angle', () => {
+      assert(math.equal(math.cis(0), 1))
+      assert(math.equal(math.cis(Math.PI/3), cplx(0.5, Math.sqrt(3)/2)))
+   })
 })
diff --git a/src/complex/relational.js b/src/complex/relational.js
index 4d6a8af..a8c58f3 100644
--- a/src/complex/relational.js
+++ b/src/complex/relational.js
@@ -13,11 +13,11 @@ export const indistinguishable = match(
          return Returns(
             BooleanT, (w, z) => same(w.re, z.re) && same(w.im, z.im))
       }
-      const [RT, AT] = T
+      const [[RT, AT]] = T
       const same = math.indistinguishable.resolve([WComp, ZComp, RT, AT])
       return Returns(
          BooleanT,
-         (w, z, [rT, aT]) => {
+         (w, z, [[rT, aT]]) => {
             return same(w.re, z.re, rT, aT) && same(w.im, z.im, rT, aT)
          })
    })
diff --git a/src/complex/type.js b/src/complex/type.js
index fbe7d8e..e83aabb 100644
--- a/src/complex/type.js
+++ b/src/complex/type.js
@@ -49,4 +49,7 @@ export const associate = match([Complex, Complex], (math, [W, Z]) => {
         const iz = mult(iZ, z)
         return eqM(w, iz) || eqNM(w, negM(iz))
     })
-})            
+})
+
+export const cis = match(NumberT, Returns(Complex(NumberT), t => ({
+    re: Math.cos(t), im: Math.sin(t)})))