diff --git a/src/boolean/BooleanT.js b/src/boolean/BooleanT.js
index f2792ed..6f4ede6 100644
--- a/src/boolean/BooleanT.js
+++ b/src/boolean/BooleanT.js
@@ -1,6 +1,7 @@
 import {Type} from '#core/Type.js'
 
 export const BooleanT = new Type(n => typeof n === 'boolean', {
+   typeName: 'BooleanT',
    zero: false,
    one: true
 })
diff --git a/src/complex/__test__/arithmetic.spec.js b/src/complex/__test__/arithmetic.spec.js
index 02dd56b..d72b335 100644
--- a/src/complex/__test__/arithmetic.spec.js
+++ b/src/complex/__test__/arithmetic.spec.js
@@ -1,5 +1,7 @@
 import assert from 'assert'
 import math from '#nanomath'
+import {Complex} from '../Complex.js'
+import {NumberT} from '#number/NumberT.js'
 
 const cplx = math.complex
 
@@ -11,16 +13,51 @@ describe('complex arithmetic operations', () => {
    })
    it('adds complex numbers', () => {
       const z = cplx(3, 4)
-      assert.deepStrictEqual(math.add(z, cplx(-1, 1)), cplx(2, 5))
-      assert.deepStrictEqual(math.add(z, cplx(true, false)), cplx(4, 4))
-      assert.deepStrictEqual(math.add(cplx(false, true), z), cplx(3, 5))
+      const add = math.add
+      assert.deepStrictEqual(add(z, cplx(-1, 1)), cplx(2, 5))
+      assert.deepStrictEqual(add(z, cplx(true, false)), cplx(4, 4))
+      assert.deepStrictEqual(add(cplx(false, true), z), cplx(3, 5))
       assert.deepStrictEqual(
-         math.add(cplx(z, z), cplx(cplx(0.5, 0.5), z)),
+         add(cplx(z, z), cplx(cplx(0.5, 0.5), z)),
          cplx(cplx(3.5, 4.5), cplx(6, 8)))
-      assert.deepStrictEqual(math.add(z, 5), cplx(8, 4))
-      assert.deepStrictEqual(math.add(true, z), cplx(4, 4))
-      assert.deepStrictEqual(math.add(cplx(z,z), 10), cplx(cplx(13, 4), z))
+      assert.deepStrictEqual(add(z, 5), cplx(8, 4))
+      assert.deepStrictEqual(add(true, z), cplx(4, 4))
+      assert.deepStrictEqual(add(cplx(z,z), 10), cplx(cplx(13, 4), z))
       assert.deepStrictEqual(
-         math.add(cplx(z,z), cplx(10,20)), cplx(cplx(13, 4), cplx(23, 4)))
+         add(cplx(z,z), cplx(10,20)), cplx(cplx(13, 4), cplx(23, 4)))
+   })
+   it('conjugates complex numbers', () => {
+      const conj = math.conj
+      const z = cplx(3, 4)
+      assert.deepStrictEqual(conj(z), cplx(3, -4))
+      assert.deepStrictEqual(conj(cplx(z,z)), cplx(cplx(3, -4), cplx(-3, -4)))
+   })
+   it('multiplies complex numbers', () => {
+      const mult = math.multiply
+      const z = cplx(3, 4)
+      assert.deepStrictEqual(mult(z, z), cplx(-7, 24))
+      assert(math.equal(mult(z, math.conj(z)), 25))
+      const q0 = cplx(cplx(1, 1), math.zero(Complex(NumberT)))
+      const q1 = cplx(cplx(1, 0.5), cplx(0.5, 0.75))
+      assert.deepStrictEqual(
+         mult(q0, q1), cplx(cplx(0.5, 1.5), cplx(1.25, 0.25)))
+      assert.deepStrictEqual(
+         mult(q0, cplx(cplx(2, 0.1), cplx(1, 0.1))),
+         cplx(cplx(1.9, 2.1), cplx(1.1, -0.9)))
+   })
+   it('subtracts complex numbers', () => {
+      const z = cplx(3, 4)
+      const sub = math.subtract
+      assert.deepStrictEqual(sub(z, cplx(-1, 1)), cplx(4, 3))
+      assert.deepStrictEqual(sub(z, cplx(true, false)), cplx(2, 4))
+      assert.deepStrictEqual(sub(cplx(false, true), z), cplx(-3, -3))
+      assert.deepStrictEqual(
+         sub(cplx(z, z), cplx(cplx(0.5, 0.5), z)),
+         cplx(cplx(2.5, 3.5), cplx(0, 0)))
+      assert.deepStrictEqual(sub(z, 5), cplx(-2, 4))
+      assert.deepStrictEqual(sub(true, z), cplx(-2, -4))
+      assert.deepStrictEqual(sub(cplx(z,z), 10), cplx(cplx(-7, 4), z))
+      assert.deepStrictEqual(
+         sub(cplx(z,z), cplx(10,20)), cplx(cplx(-7, 4), cplx(-17, 4)))
    })
 })
diff --git a/src/complex/__test__/type.spec.js b/src/complex/__test__/type.spec.js
index a0c42cf..b85797f 100644
--- a/src/complex/__test__/type.spec.js
+++ b/src/complex/__test__/type.spec.js
@@ -15,4 +15,21 @@ describe('complex type operations', () => {
       assert.strictEqual(math.arg(cplx(1, Math.sqrt(3))), Math.PI/3)
       assert.strictEqual(math.arg(cplx(true, true)), Math.PI/4)
    })
+   it('detects associates of a complex number', () => {
+      const z = cplx(3, 4)
+      const assoc = math.associate
+      assert(assoc(z, z))
+      assert(assoc(z, cplx(-3, -4)))
+      assert(assoc(z, cplx(-4, 3)))
+      assert(assoc(z, cplx(4, -3)))
+      assert(!assoc(z, math.conj(z)))
+      const b = cplx(true, true)
+      assert(assoc(b, cplx(-1, 1)))
+      assert(assoc(cplx(1, 1), b))
+      assert(assoc(cplx(-1, -1), b))
+      assert(assoc(cplx(1, -1), b))
+      assert(assoc(cplx(-1, 1), b))
+      assert(!assoc(b, cplx(false, true)))
+      assert(!assoc(cplx(0, 1), b))
+   })
 })
diff --git a/src/complex/all.js b/src/complex/all.js
index 5c261d4..8ccff17 100644
--- a/src/complex/all.js
+++ b/src/complex/all.js
@@ -1,3 +1,4 @@
 export * as typeDefinition from './Complex.js'
 export * as arithmetic from './arithmetic.js'
+export * as relational from './relational.js'
 export * as type from './type.js'
diff --git a/src/complex/arithmetic.js b/src/complex/arithmetic.js
index 75a91ea..70fafae 100644
--- a/src/complex/arithmetic.js
+++ b/src/complex/arithmetic.js
@@ -1,17 +1,44 @@
 import {Complex} from './Complex.js'
+import {promoteBinary, promoteUnary} from './helpers.js'
+import {ResolutionError} from '#core/helpers.js'
 import {match} from '#core/TypePatterns.js'
 import {ReturnsAs} from '#generic/helpers.js'
 
 export const absquare = match(Complex, (math, C) => {
-    const compAbsq = math.absquare.resolve([C.Component])
-    const R = compAbsq.returns
-    const add = math.add.resolve([R,R])
-    return ReturnsAs(add, z => add(compAbsq(z.re), compAbsq(z.im)))
+   const compAbsq = math.absquare.resolve([C.Component])
+   const R = compAbsq.returns
+   const add = math.add.resolve([R,R])
+   return ReturnsAs(add, z => add(compAbsq(z.re), compAbsq(z.im)))
 })
 
-export const add = match([Complex, Complex], (math, [C, D]) => {
-    const addComps = math.add.resolve([C.Component, D.Component])
-    const cplx = math.complex.resolve([addComps.returns, addComps.returns])
-    return ReturnsAs(
-        cplx, (w,z) => cplx(addComps(w.re, z.re), addComps(w.im, z.im)))
+export const add = promoteBinary('add')
+
+export const conj = match(Complex, (math, C) => {
+   const neg = math.negate.resolve(C.Component)
+   const compConj = math.conj.resolve(C.Component)
+   const cplx = math.complex.resolve([compConj.returns, neg.returns])
+   return ReturnsAs(cplx, z => cplx(compConj(z.re), neg(z.im)))
 })
+
+// We want this to work for complex numbers, quaternions, octonions, etc
+// See https://math.ucr.edu/home/baez/octonions/node5.html
+export const multiply = match([Complex, Complex], (math, [W, Z]) => {
+   const conj = math.conj.resolve(W.Component)
+   if (conj.returns !== W.Component) {
+      throw new ResolutionError(
+         `conjugation on ${W.Component} returns other type (${conj.returns})`)
+   }
+   const mWZ = math.multiply.resolve([W.Component, Z.Component])
+   const mZW = math.multiply.resolve([Z.Component, W.Component])
+   const sub = math.subtract.resolve([mWZ.returns, mZW.returns])
+   const add = math.add.resolve([mWZ.returns, mZW.returns])
+   const cplx = math.complex.resolve([sub.returns, add.returns])
+   return ReturnsAs(cplx, (w, z) => {
+      const real = sub(mWZ(     w.re,  z.re), mZW(z.im, conj(w.im)))
+      const imag = add(mWZ(conj(w.re), z.im), mZW(z.re,      w.im))
+      return cplx(real, imag)
+   })
+})
+
+export const negate = promoteUnary('negate')
+export const subtract = promoteBinary('subtract')
diff --git a/src/complex/helpers.js b/src/complex/helpers.js
new file mode 100644
index 0000000..84e828f
--- /dev/null
+++ b/src/complex/helpers.js
@@ -0,0 +1,20 @@
+import {Complex} from './Complex.js'
+import {match} from '#core/TypePatterns.js'
+import {ReturnsAs} from '#generic/helpers.js'
+
+export const promoteUnary = name => match(
+   Complex,
+   (math, C) => {
+      const compOp = math.resolve(name, C.Component)
+      const cplx = math.complex.resolve([compOp.returns, compOp.returns])
+      return ReturnsAs(cplx, z => cplx(compOp(z.re), compOp(z.im)))
+   })
+
+export const promoteBinary = name => match(
+   [Complex, Complex],
+   (math, [W, Z]) => {
+      const compOp = math.resolve(name, [W.Component, Z.Component])
+      const cplx = math.complex.resolve([compOp.returns, compOp.returns])
+      return ReturnsAs(
+         cplx, (w, z) => cplx(compOp(w.re, z.re), compOp(w.im, z.im)))
+   })
diff --git a/src/complex/relational.js b/src/complex/relational.js
new file mode 100644
index 0000000..4d6a8af
--- /dev/null
+++ b/src/complex/relational.js
@@ -0,0 +1,24 @@
+import {Complex} from './Complex.js'
+import {BooleanT} from '#boolean/BooleanT.js'
+import {Returns} from '#core/Type.js'
+import {match, Any, Optional} from '#core/TypePatterns.js'
+
+export const indistinguishable = match(
+   [Complex, Complex, Optional([Any, Any])],
+   (math, [W, Z, T]) => {
+      let WComp = W.Component
+      let ZComp = Z.Component
+      if (T.length === 0) { // no tolerances
+         const same = math.indistinguishable.resolve([WComp, ZComp])
+         return Returns(
+            BooleanT, (w, z) => same(w.re, z.re) && same(w.im, z.im))
+      }
+      const [RT, AT] = T
+      const same = math.indistinguishable.resolve([WComp, ZComp, RT, AT])
+      return Returns(
+         BooleanT,
+         (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 6c0f410..fbe7d8e 100644
--- a/src/complex/type.js
+++ b/src/complex/type.js
@@ -1,6 +1,7 @@
 import {Complex} from './Complex.js'
 import {Returns} from "#core/Type.js"
 import {Any, match} from "#core/TypePatterns.js"
+import {BooleanT} from '#boolean/BooleanT.js'
 import {NumberT} from '#number/NumberT.js'
 
 export const complex = [
@@ -28,3 +29,24 @@ export const complex = [
 
 export const arg = match(
     Complex(NumberT), Returns(NumberT, z => Math.atan2(z.im, z.re)))
+
+/* Returns true if w is z multiplied by a complex unit */
+export const associate = match([Complex, Complex], (math, [W, Z]) => {
+    if (Z.Component.complex) {
+        throw new Error(
+            `The group of units of type ${Z} is not yet implemented`)
+    }
+    const eq = math.equal.resolve([W, Z])
+    const neg = math.negate.resolve(Z)
+    const eqN = math.equal.resolve([W, neg.returns])
+    const mult = math.multiply.resolve([Z, Z])
+    const eqM = math.equal.resolve([W, mult.returns])
+    const negM = math.negate.resolve(mult.returns)
+    const eqNM = math.equal.resolve([W, negM.returns])
+    const iZ = math.complex(math.zero(Z.Component), math.one(Z.Component))
+    return Returns(BooleanT, (w, z) => {
+        if (eq(w, z) || eqN(w, neg(z))) return true
+        const iz = mult(iZ, z)
+        return eqM(w, iz) || eqNM(w, negM(iz))
+    })
+})            
diff --git a/src/core/TypeDispatcher.js b/src/core/TypeDispatcher.js
index 9eaa6da..2b997e6 100644
--- a/src/core/TypeDispatcher.js
+++ b/src/core/TypeDispatcher.js
@@ -8,6 +8,8 @@ import {
    matched, needsCollection, Passthru, Matcher, match
 } from './TypePatterns.js'
 
+const underResolution = Symbol('underResolution')
+
 export class TypeDispatcher {
    constructor(...specs) {
       this._implementations = {} // maps key to list of [pattern, result] pairs
@@ -261,6 +263,7 @@ export class TypeDispatcher {
       if (!(key in this)) {
          throw new ReferenceError(`no method or value for key '${key}'`)
       }
+      if (!Array.isArray(types)) types = [types]
 
       const generatingDeps = this.resolve._genDepsOf?.length
       if (generatingDeps) this._addToDeps(key, types)
@@ -269,6 +272,10 @@ export class TypeDispatcher {
       // Return the cached resolution if it's there
       if (behave.has(types)) {
          const result = behave.get(types)
+         if (result === underResolution) {
+            throw new ResolutionError(
+               `recursive resolution of ${key} on ${types}`)
+         }
          if (generatingDeps
              && typeof result === 'object'
              && !(result instanceof Type)
@@ -328,6 +335,7 @@ export class TypeDispatcher {
       let theBehavior = () => undefined
       let finalBehavior
       this.resolve._genDepsOf.push([key, types])
+      behave.set(types, underResolution)
       try { // Used to make sure not to return without popping _genDepsOf
          if (!('returns' in item)) {
             // looks like a factory
diff --git a/src/generic/arithmetic.js b/src/generic/arithmetic.js
index 7c7c327..cf67fdc 100644
--- a/src/generic/arithmetic.js
+++ b/src/generic/arithmetic.js
@@ -1,6 +1,7 @@
 import {Returns} from '#core/Type.js'
 import {match, Any} from '#core/TypePatterns.js'
 
+export const conj = match(Any, (_math, T) => Returns(T, a => a))
 export const square = match(Any, (math, T) => {
    const mult = math.multiply.resolve([T, T])
    return Returns(mult.returns, a => mult(a, a))
diff --git a/src/nanomath.js b/src/nanomath.js
index 3038472..ddeeeba 100644
--- a/src/nanomath.js
+++ b/src/nanomath.js
@@ -10,9 +10,11 @@ import {TypeDispatcher} from '#core/TypeDispatcher.js'
 // the following list will be tried earlier. (The rationale for that
 // ordering is that any time you merge something, it should supersede
 // whatever has been merged before.)
-// Hence, in building the math instance, we put complex first because
-// we want its conversion (which converts _any_ non-complex type to
-// complex, potentially making a poor overload choice) to be tried last.
-const math = new TypeDispatcher(complex, generics, booleans, coretypes, numbers)
+// Hence, in building the math instance, we put generics first because
+// they should only kick in when there are not specific implementations,
+// and complex next becausewe want its conversion (which converts _any_
+// non-complex type to complex, potentially making a poor overload choice)
+// to be tried last.
+const math = new TypeDispatcher(generics, complex, booleans, coretypes, numbers)
 
 export default math
diff --git a/src/number/NumberT.js b/src/number/NumberT.js
index b915b85..415a37d 100644
--- a/src/number/NumberT.js
+++ b/src/number/NumberT.js
@@ -4,6 +4,7 @@ import {BooleanT} from '#boolean/BooleanT.js'
 
 export const NumberT = new Type(n => typeof n === 'number', {
     from: match(BooleanT, math => math.number.resolve([BooleanT])),
+    typeName: 'NumberT', // since used before ever put in a TypeDispatcher
     one: 1,
     zero: 0,
     nan: NaN