diff --git a/package.json5 b/package.json5
index f83ee88..a0647ae 100644
--- a/package.json5
+++ b/package.json5
@@ -1,8 +1,7 @@
 {
   name: 'pocomath',
   version: '0.0.0',
-  description: 'A little proof-of-concept for organizing mathjs by module\
-    inclusion, avoiding factory functions.',
+  description: 'A little proof-of-concept for organizing mathjs by module    inclusion, avoiding factory functions.',
   main: 'index.js',
   scripts: {
     'test:filecase': '!(find . | sort -f | uniq -i -c | grep -v " 1 ")',
@@ -24,6 +23,7 @@
     mocha: '^10.0.0',
   },
   dependencies: {
+    'bigint-isqrt': '^0.2.1',
     'typed-function': '^3.0.0',
   },
 }
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 22e3de7..4063068 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -1,10 +1,12 @@
 lockfileVersion: 5.4
 
 specifiers:
+  bigint-isqrt: ^0.2.1
   mocha: ^10.0.0
   typed-function: ^3.0.0
 
 dependencies:
+  bigint-isqrt: 0.2.1
   typed-function: 3.0.0
 
 devDependencies:
@@ -49,6 +51,10 @@ packages:
     resolution: {integrity: sha512-3oSeUO0TMV67hN1AmbXsK4yaqU7tjiHlbxRDZOpH0KW9+CeX4bRAaX0Anxt0tx2MrpRpWwQaPwIlISEJhYU5Pw==}
     dev: true
 
+  /bigint-isqrt/0.2.1:
+    resolution: {integrity: sha512-x43s2Qx5l5ShFZFA5xejJfPtV1vXISyWUXlrZeJTx9F6D2ex3BR6AwWnIz4ITAu5nTy3hp+d+ClGu7qUGcgY8g==}
+    dev: false
+
   /binary-extensions/2.2.0:
     resolution: {integrity: sha512-jDctJ/IVQbZoJykoeHbhXpOlNBqGNcwXJKJog42E5HDPUwQTSdjCHdihjj0DlnheQ7blbT6dHOafNAiS8ooQKA==}
     engines: {node: '>=8'}
diff --git a/src/bigint/Types/bigint.mjs b/src/bigint/Types/bigint.mjs
index 04bd189..c1416af 100644
--- a/src/bigint/Types/bigint.mjs
+++ b/src/bigint/Types/bigint.mjs
@@ -1,6 +1,4 @@
-export const Types = {
-    bigint: {
-        before: ['Complex'],
-        test: b => typeof b === 'bigint'
-    }
+export const Type_bigint = {
+    before: ['Complex'],
+    test: b => typeof b === 'bigint'
 }
diff --git a/src/bigint/add.mjs b/src/bigint/add.mjs
index cc1f48e..31e2926 100644
--- a/src/bigint/add.mjs
+++ b/src/bigint/add.mjs
@@ -1,4 +1,4 @@
-export {Types} from './Types/bigint.mjs'
+export * from './Types/bigint.mjs'
 
 export const add = {
    '...bigint': () => addends => addends.reduce((x,y) => x+y, 0n)
diff --git a/src/bigint/all.mjs b/src/bigint/all.mjs
index f4cdb60..0f87414 100644
--- a/src/bigint/all.mjs
+++ b/src/bigint/all.mjs
@@ -1,4 +1,8 @@
-export {Types} from './Types/bigint.mjs'
-export {add} from './add.mjs'
-export {negate} from './negate.mjs'
-export {subtract} from '../generic/subtract.mjs'
+export * from './native.mjs'
+export * from '../generic/arithmetic.mjs'
+
+// resolve the conflicts
+export {divide} from './divide.mjs'
+export {multiply} from './multiply.mjs'
+export {sign} from './sign.mjs'
+export {sqrt} from './sqrt.mjs'
diff --git a/src/bigint/divide.mjs b/src/bigint/divide.mjs
new file mode 100644
index 0000000..288230d
--- /dev/null
+++ b/src/bigint/divide.mjs
@@ -0,0 +1,20 @@
+export * from './Types/bigint.mjs'
+
+export const divide = {
+   'bigint,bigint': ({config, 'sign(bigint)': sgn}) => {
+      if (config.predictable) {
+         return (n, d) => {
+            if (sgn(n) === sgn(d)) return n/d
+            const quot = n/d
+            if (quot * d == n) return quot
+            return quot - 1n
+         }
+      } else {
+         return (n, d) => {
+            const quot = n/d
+            if (quot * d == n) return quot
+            return undefined
+         }
+      }
+   }
+}
diff --git a/src/bigint/multiply.mjs b/src/bigint/multiply.mjs
new file mode 100644
index 0000000..7994abc
--- /dev/null
+++ b/src/bigint/multiply.mjs
@@ -0,0 +1,5 @@
+export * from './Types/bigint.mjs'
+
+export const multiply = {
+   '...bigint': () => multiplicands => multiplicands.reduce((x,y) => x*y, 1n)
+}
diff --git a/src/bigint/native.mjs b/src/bigint/native.mjs
new file mode 100644
index 0000000..b09076a
--- /dev/null
+++ b/src/bigint/native.mjs
@@ -0,0 +1,9 @@
+export * from './Types/bigint.mjs'
+export {add} from './add.mjs'
+export {divide} from './divide.mjs'
+export {multiply} from './multiply.mjs'
+export {negate} from './negate.mjs'
+export {one} from './one.mjs'
+export {sign} from './sign.mjs'
+export {sqrt} from './sqrt.mjs'
+export {zero} from './zero.mjs'
diff --git a/src/bigint/negate.mjs b/src/bigint/negate.mjs
index 874a377..d44cdb0 100644
--- a/src/bigint/negate.mjs
+++ b/src/bigint/negate.mjs
@@ -1,3 +1,3 @@
-export {Types} from './Types/bigint.mjs'
+export * from './Types/bigint.mjs'
 
 export const negate = {bigint: () => b => -b}
diff --git a/src/bigint/one.mjs b/src/bigint/one.mjs
new file mode 100644
index 0000000..f548a65
--- /dev/null
+++ b/src/bigint/one.mjs
@@ -0,0 +1,3 @@
+export * from './Types/bigint.mjs'
+
+export const one = {bigint: () => () => 1n}
diff --git a/src/bigint/sign.mjs b/src/bigint/sign.mjs
new file mode 100644
index 0000000..af48e05
--- /dev/null
+++ b/src/bigint/sign.mjs
@@ -0,0 +1,9 @@
+export * from './Types/bigint.mjs'
+
+export const sign = {
+   bigint: () => b => {
+      if (b === 0n) return 0n
+      if (b > 0n) return 1n
+      return -1n
+   }
+}
diff --git a/src/bigint/sqrt.mjs b/src/bigint/sqrt.mjs
new file mode 100644
index 0000000..ad6bd67
--- /dev/null
+++ b/src/bigint/sqrt.mjs
@@ -0,0 +1,30 @@
+export * from './Types/bigint.mjs'
+import isqrt from 'bigint-isqrt'
+
+export const sqrt = {
+   bigint: ({config, complex, 'self(Complex)': complexSqrt}) => {
+      if (config.predictable) {
+         // Don't just return the constant isqrt here because the object
+         // gets decorated with info that might need to be different
+         // for different PocomathInstancss
+         return b => isqrt(b)
+      }
+      if (!complexSqrt) {
+         return b => {
+            if (b >= 0n) {
+               const trial = isqrt(b)
+               if (trial * trial === b) return trial
+            }
+            return undefined
+         }
+      }
+      return b => {
+         if (b >= 0n) {
+            const trial = isqrt(b)
+            if (trial * trial === b) return trial
+            return undefined
+         }
+         return complexSqrt(complex(b))
+      }
+   }
+}
diff --git a/src/bigint/zero.mjs b/src/bigint/zero.mjs
new file mode 100644
index 0000000..0c63a1a
--- /dev/null
+++ b/src/bigint/zero.mjs
@@ -0,0 +1,3 @@
+export * from './Types/bigint.mjs'
+
+export const zero = {bigint: () => () => 0n}
diff --git a/src/complex/Types/Complex.mjs b/src/complex/Types/Complex.mjs
index f6e3eb2..30bbf3f 100644
--- a/src/complex/Types/Complex.mjs
+++ b/src/complex/Types/Complex.mjs
@@ -2,21 +2,15 @@
  * can be any type (for this proof-of-concept; in reality we'd want to
  * insist on some numeric or scalar supertype).
  */
-export function isComplex(z) { 
+function isComplex(z) { 
    return z && typeof z === 'object' && 're' in z && 'im' in z
 }
 
-export const Types = {
-   Complex: {
-      test: isComplex,
-      from: {
-         number: x => ({re: x, im: 0}),
-         bigint: x => ({re: x, im: 0n})
-      }
+export const Type_Complex = {
+   test: isComplex,
+   from: {
+      number: x => ({re: x, im: 0}),
+      bigint: x => ({re: x, im: 0n})
    }
 }
 
-/* test if an entity is Complex<number>, so to speak: */
-export function numComplex(z) {
-   return isComplex(z) && typeof z.re === 'number' && typeof z.im === 'number'
-}
diff --git a/src/complex/abs.mjs b/src/complex/abs.mjs
index 20ab809..63aacd6 100644
--- a/src/complex/abs.mjs
+++ b/src/complex/abs.mjs
@@ -1,4 +1,4 @@
-export {Types} from './Types/Complex.mjs'
+export * from './Types/Complex.mjs'
 
 export const abs = {Complex: ({sqrt, add, multiply}) => z => {
     return sqrt(add(multiply(z.re, z.re), multiply(z.im, z.im)))
diff --git a/src/complex/add.mjs b/src/complex/add.mjs
index 27374b6..58d9eea 100644
--- a/src/complex/add.mjs
+++ b/src/complex/add.mjs
@@ -1,4 +1,4 @@
-export {Types} from './Types/Complex.mjs'
+export * from './Types/Complex.mjs'
 
 export const add = {
    '...Complex': ({self}) => addends => {
diff --git a/src/complex/all.mjs b/src/complex/all.mjs
index 2c3946d..ddb7679 100644
--- a/src/complex/all.mjs
+++ b/src/complex/all.mjs
@@ -1,2 +1,5 @@
-export * from './native.mjs'
 export * from '../generic/arithmetic.mjs'
+export * from './native.mjs'
+
+// resolve the conflicts
+export {sqrt} from './sqrt.mjs'
diff --git a/src/complex/complex.mjs b/src/complex/complex.mjs
index 5cbbced..58d3e2e 100644
--- a/src/complex/complex.mjs
+++ b/src/complex/complex.mjs
@@ -1,11 +1,15 @@
-export {Types} from './Types/Complex.mjs'
+export * from './Types/Complex.mjs'
+export * from '../generic/Types/generic.mjs'
 
 export const complex = {
    /* Very permissive for sake of proof-of-concept; would be better to
     * have a numeric/scalar type, e.g. by implementing subtypes in
     * typed-function
     */
-   'any, any': () => (x, y) => ({re: x, im: y}),
+   'undefined': () => u => u,
+   'undefined,any': () => (u, y) => u,
+   'any,undefined': () => (x, u) => u,
+   'any,any': () => (x, y) => ({re: x, im: y}),
    /* Take advantage of conversions in typed-function */
    Complex: () => z => z
 }
diff --git a/src/complex/native.mjs b/src/complex/native.mjs
index aec0868..03652ed 100644
--- a/src/complex/native.mjs
+++ b/src/complex/native.mjs
@@ -1,4 +1,4 @@
-export {Types} from './Types/Complex.mjs'
+export * from './Types/Complex.mjs'
 
 export {abs} from './abs.mjs'
 export {add} from './add.mjs'
diff --git a/src/complex/negate.mjs b/src/complex/negate.mjs
index 45b9840..7ddaecc 100644
--- a/src/complex/negate.mjs
+++ b/src/complex/negate.mjs
@@ -1,4 +1,4 @@
-export {Types} from './Types/Complex.mjs'
+export * from './Types/Complex.mjs'
 
 export const negate = {
    Complex: ({self}) => z => ({re: self(z.re), im: self(z.im)})
diff --git a/src/complex/sqrt.mjs b/src/complex/sqrt.mjs
index 93cd10a..cba7361 100644
--- a/src/complex/sqrt.mjs
+++ b/src/complex/sqrt.mjs
@@ -1,35 +1,44 @@
-export { Types } from './Types/Complex.mjs'
+export * from './Types/Complex.mjs'
 
 export const sqrt = {
    Complex: ({
       config,
+      zero,
+      sign,
+      one,
+      add,
       complex,
       multiply,
-      sign,
       self,
       divide,
-      add,
       'abs(Complex)': abs,
       subtract
    }) => {
       if (config.predictable) {
          return z => {
+            const imZero = zero(z.im)
             const imSign = sign(z.im)
+            const reOne = one(z.re)
             const reSign = sign(z.re)
-            if (imSign === 0 && reSign === 1) return complex(self(z.re))
+            if (imSign === imZero && reSign === reOne) return complex(self(z.re))
+            const reTwo = add(reOne, reOne)
             return complex(
-               multiply(sign(z.im), self(divide(add(abs(z),z.re), 2))),
-               self(divide(subtract(abs(z),z.re), 2))
+               multiply(sign(z.im), self(divide(add(abs(z),z.re), reTwo))),
+               self(divide(subtract(abs(z),z.re), reTwo))
             )
          }
       }
       return z => {
+         const imZero = zero(z.im)
          const imSign = sign(z.im)
+         const reOne = one(z.re)
          const reSign = sign(z.re)
-         if (imSign === 0 && reSign === 1) return self(z.re)
+         if (imSign === imZero && reSign === reOne) return self(z.re)
+         const reTwo = add(reOne, reOne)
+         const partial = add(abs(z), z.re)
          return complex(
-            multiply(sign(z.im), self(divide(add(abs(z),z.re), 2))),
-            self(divide(subtract(abs(z),z.re), 2))
+            multiply(sign(z.im), self(divide(add(abs(z),z.re), reTwo))),
+            self(divide(subtract(abs(z),z.re), reTwo))
          )
       }
    }
diff --git a/src/core/PocomathInstance.mjs b/src/core/PocomathInstance.mjs
index 646bd62..7462082 100644
--- a/src/core/PocomathInstance.mjs
+++ b/src/core/PocomathInstance.mjs
@@ -8,7 +8,8 @@ export default class PocomathInstance {
     * in that if a new top-level PocomathInstance method is added, its name
     * must be added to this list.
     */
-   static reserved = new Set(['config', 'importDependencies', 'install', 'name'])
+   static reserved = new Set([
+      'config', 'importDependencies', 'install', 'name', 'Types'])
 
    constructor(name) {
       this.name = name
@@ -65,10 +66,11 @@ export default class PocomathInstance {
     *    operation in the body of the implementation. [NOTE: this signature-
     *    specific reference is not yet implemented.]
     *
-    *    Note that the "operation" named `Types` is special: it gives
-    *    types that must be installed in the instance. In this case, the keys
-    *    are type names, and the values are plain objects with the following
-    *    properties:
+    *    Note that any "operation" whose name begins with  `Type_` is special:
+    *    it defines a types that must be installed in the instance.
+    *    The remainder of the "operation" name following the `_` is the
+    *    name of the type. The value of the "operation" should be a plain
+    *    object with the following properties:
     *
     *    - test: the predicate for the type
     *    - from: a plain object mapping the names of types that can be converted
@@ -78,8 +80,8 @@ export default class PocomathInstance {
     */
    install(ops) {
       for (const [item, spec] of Object.entries(ops)) {
-         if (item === 'Types') {
-            this._installTypes(spec)
+         if (item.slice(0,5) === 'Type_') {
+            this._installType(item.slice(5), spec)
          } else {
             this._installOp(item, spec)
          }
@@ -128,43 +130,40 @@ export default class PocomathInstance {
    /* Used internally by install, see the documentation there.
     * Note that unlike _installOp below, we can do this immediately
     */
-   _installTypes(typeSpecs) {
-      for (const [type, spec] of Object.entries(typeSpecs)) {
-         if (type in this.Types) {
-            if (spec !== this.Types[type]) {
-                  throw new SyntaxError(
-                     `Conflicting definitions of type ${type}`)
-            }
-            continue
+   _installType(type, spec) {
+      if (type in this.Types) {
+         if (spec !== this.Types[type]) {
+            throw new SyntaxError(`Conflicting definitions of type ${type}`)
          }
-         let beforeType = 'any'
-         for (const other of spec.before || []) {
-            if (other in this.Types) {
-               beforeType = other
-               break
-            }
-         }
-         this._typed.addTypes([{name: type, test: spec.test}], beforeType)
-         /* Now add conversions to this type */
-         for (const from in (spec.from || {})) {
-            if (from in this.Types) {
-               this._typed.addConversion(
-                  {from, to: type, convert: spec.from[from]})
-            }
-         }
-         /* And add conversions from this type */
-         for (const to in this.Types) {
-            if (type in (this.Types[to].from || {})) {
-               this._typed.addConversion(
-                  {from: type, to, convert: this.Types[to].from[type]})
-            }
-         }
-         this.Types[type] = spec
-         // rebundle anything that uses the new type:
-         this._invalidateDependents(':' + type)
+         return
       }
+      let beforeType = 'any'
+      for (const other of spec.before || []) {
+         if (other in this.Types) {
+            beforeType = other
+            break
+         }
+      }
+      this._typed.addTypes([{name: type, test: spec.test}], beforeType)
+      /* Now add conversions to this type */
+      for (const from in (spec.from || {})) {
+         if (from in this.Types) {
+            this._typed.addConversion(
+               {from, to: type, convert: spec.from[from]})
+         }
+      }
+      /* And add conversions from this type */
+      for (const to in this.Types) {
+         if (type in (this.Types[to].from || {})) {
+            this._typed.addConversion(
+               {from: type, to, convert: this.Types[to].from[type]})
+         }
+      }
+      this.Types[type] = spec
+      // rebundle anything that uses the new type:
+      this._invalidateDependents(':' + type)
    }
-         
+
    /* Used internally by install, see the documentation there */
    _installOp(name, implementations) {
       if (name.charAt(0) === '_') {
diff --git a/src/generic/Types/generic.mjs b/src/generic/Types/generic.mjs
new file mode 100644
index 0000000..473ec56
--- /dev/null
+++ b/src/generic/Types/generic.mjs
@@ -0,0 +1,2 @@
+export const Type_undefined = {test: u => u === undefined}
+
diff --git a/src/generic/arithmetic.mjs b/src/generic/arithmetic.mjs
index 2787c41..e466b1f 100644
--- a/src/generic/arithmetic.mjs
+++ b/src/generic/arithmetic.mjs
@@ -1,3 +1,7 @@
+export * from './Types/generic.mjs'
+
+export {multiply} from './multiply.mjs'
 export {divide} from './divide.mjs'
 export {sign} from './sign.mjs'
+export {sqrt} from './sqrt.mjs'
 export {subtract} from './subtract.mjs'
diff --git a/src/generic/multiply.mjs b/src/generic/multiply.mjs
new file mode 100644
index 0000000..dc078d9
--- /dev/null
+++ b/src/generic/multiply.mjs
@@ -0,0 +1,12 @@
+export * from './Types/generic.mjs'
+
+export const multiply = {
+   'undefined': () => u => u,
+   'undefined,...any': () => (u, rest) => u,
+   'any,undefined': () => (x, u) => u,
+   'any,undefined,...any': () => (x, u, rest) => u,
+   'any,any,undefined': () => (x, y, u) => u,
+   'any,any,undefined,...any': () => (x, y, u, rest) => u
+   // Bit of a hack since this should go on indefinitely...
+}
+
diff --git a/src/generic/sqrt.mjs b/src/generic/sqrt.mjs
new file mode 100644
index 0000000..21aa1d5
--- /dev/null
+++ b/src/generic/sqrt.mjs
@@ -0,0 +1,3 @@
+export * from './Types/generic.mjs'
+
+export const sqrt = {undefined: () => () => undefined}
diff --git a/src/number/Types/number.mjs b/src/number/Types/number.mjs
index 417d6f6..f8179fc 100644
--- a/src/number/Types/number.mjs
+++ b/src/number/Types/number.mjs
@@ -1,8 +1,6 @@
-export const Types = {
-    number: {
-        before: ['Complex'],
-        test: n => typeof n === 'number',
-        from: {string: s => +s}
-    }
+export const Type_number = {
+    before: ['Complex'],
+    test: n => typeof n === 'number',
+    from: {string: s => +s}
 }
 
diff --git a/src/number/abs.mjs b/src/number/abs.mjs
index 1613356..66ede16 100644
--- a/src/number/abs.mjs
+++ b/src/number/abs.mjs
@@ -1,3 +1,3 @@
-export {Types} from './Types/number.mjs'
+export * from './Types/number.mjs'
 
 export const abs = {number: () => n => Math.abs(n)}
diff --git a/src/number/add.mjs b/src/number/add.mjs
index e473c50..e6610ee 100644
--- a/src/number/add.mjs
+++ b/src/number/add.mjs
@@ -1,4 +1,4 @@
-export {Types} from './Types/number.mjs'
+export * from './Types/number.mjs'
 
 export const add = {
    '...number': () => addends => addends.reduce((x,y) => x+y, 0),
diff --git a/src/number/all.mjs b/src/number/all.mjs
index e437adb..ef8823e 100644
--- a/src/number/all.mjs
+++ b/src/number/all.mjs
@@ -1,4 +1,6 @@
-export {Types} from './Types/number.mjs'
-
-export * from './native.mjs'
 export * from '../generic/arithmetic.mjs'
+export * from './native.mjs'
+
+// resolve the conflicts
+export {sqrt} from './sqrt.mjs'
+export {multiply} from './multiply.mjs'
diff --git a/src/number/invert.mjs b/src/number/invert.mjs
index 11d24c3..4eabe2f 100644
--- a/src/number/invert.mjs
+++ b/src/number/invert.mjs
@@ -1,3 +1,3 @@
-export {Types} from './Types/number.mjs'
+export * from './Types/number.mjs'
 
 export const invert = {number: () => n => 1/n}
diff --git a/src/number/multiply.mjs b/src/number/multiply.mjs
index dff6611..8d7f797 100644
--- a/src/number/multiply.mjs
+++ b/src/number/multiply.mjs
@@ -1,4 +1,4 @@
-export {Types} from './Types/number.mjs'
+export * from './Types/number.mjs'
 
 export const multiply = {
    '...number': () => multiplicands => multiplicands.reduce((x,y) => x*y, 1),
diff --git a/src/number/native.js b/src/number/native.js
deleted file mode 100644
index 208d8a2..0000000
--- a/src/number/native.js
+++ /dev/null
@@ -1,4 +0,0 @@
-export {Types} from './Types/number.mjs'
-export {add} from './add.mjs'
-export {negate} from './negate.mjs'
-export {sqrt} from './sqrt.mjs'
diff --git a/src/number/native.mjs b/src/number/native.mjs
index 99807de..1053579 100644
--- a/src/number/native.mjs
+++ b/src/number/native.mjs
@@ -1,8 +1,10 @@
-export {Types} from './Types/number.mjs'
+export * from './Types/number.mjs'
 
 export {abs} from './abs.mjs'
 export {add} from './add.mjs'
 export {invert} from './invert.mjs'
 export {multiply} from './multiply.mjs'
 export {negate} from './negate.mjs'
+export {one} from './one.mjs'
 export {sqrt} from './sqrt.mjs'
+export {zero} from './zero.mjs'
diff --git a/src/number/negate.mjs b/src/number/negate.mjs
index 387d905..82e27d0 100644
--- a/src/number/negate.mjs
+++ b/src/number/negate.mjs
@@ -1,3 +1,3 @@
-export { Types } from './Types/number.mjs'
+export * from './Types/number.mjs'
 
 export const negate = {number: () => n => -n}
diff --git a/src/number/one.mjs b/src/number/one.mjs
new file mode 100644
index 0000000..5726468
--- /dev/null
+++ b/src/number/one.mjs
@@ -0,0 +1,3 @@
+export * from './Types/number.mjs'
+
+export const one = {number: () => () => 1}
diff --git a/src/number/sqrt.mjs b/src/number/sqrt.mjs
index 179aa0a..f6cc459 100644
--- a/src/number/sqrt.mjs
+++ b/src/number/sqrt.mjs
@@ -1,4 +1,4 @@
-export { Types } from './Types/number.mjs'
+export * from './Types/number.mjs'
 
 export const sqrt = {
    number: ({config, complex, 'self(Complex)': complexSqrt}) => {
diff --git a/src/number/zero.mjs b/src/number/zero.mjs
new file mode 100644
index 0000000..40ac2fb
--- /dev/null
+++ b/src/number/zero.mjs
@@ -0,0 +1,3 @@
+export * from './Types/number.mjs'
+
+export const zero = {number: () => () => 0}
diff --git a/src/pocomath.mjs b/src/pocomath.mjs
index e0015a9..6b61f4f 100644
--- a/src/pocomath.mjs
+++ b/src/pocomath.mjs
@@ -1,7 +1,7 @@
 /* Core of pocomath: generates the default instance */
 import PocomathInstance from './core/PocomathInstance.mjs'
 import * as numbers from './number/native.mjs'
-import * as bigints from './bigint/all.mjs'
+import * as bigints from './bigint/native.mjs'
 import * as complex from './complex/native.mjs'
 import * as generic from './generic/all.mjs'
 
diff --git a/test/_pocomath.mjs b/test/_pocomath.mjs
index 7f130dc..e7b30e0 100644
--- a/test/_pocomath.mjs
+++ b/test/_pocomath.mjs
@@ -22,11 +22,9 @@ describe('The default full pocomath instance "math"', () => {
          add: {
             '...stringK': () => addends => addends.reduce((x,y) => x+y, '')
          },
-         Types: {
-            stringK: {
-               test: s => typeof s === 'string' && s.charAt(0) === 'K',
-               before: ['string']
-            }
+         Type_stringK: {
+            test: s => typeof s === 'string' && s.charAt(0) === 'K',
+            before: ['string']
          }
       })
       assert.strictEqual(math.add('Kilroy','K is here'), 'KilroyK is here')
diff --git a/test/bigint/_all.mjs b/test/bigint/_all.mjs
new file mode 100644
index 0000000..9c80df3
--- /dev/null
+++ b/test/bigint/_all.mjs
@@ -0,0 +1,55 @@
+import assert from 'assert'
+import math from '../../src/pocomath.mjs'
+import PocomathInstance from '../../src/core/PocomathInstance.mjs'
+import * as bigintSqrt from '../../src/bigint/sqrt.mjs'
+import * as complex from '../../src/complex/all.mjs'
+import * as bigints from '../../src/bigint/all.mjs'
+
+describe('bigint', () => {
+   it('can divide', () => {
+      assert.strictEqual(math.divide(15n, 5n), 3n)
+      assert.strictEqual(math.divide(14n, 5n), undefined)
+      math.config.predictable = true
+      assert.strictEqual(math.divide(14n, 5n), 2n)
+      assert.strictEqual(math.divide(-14n, 5n), -3n)
+      assert.strictEqual(math.divide(14n, -5n), -3n)
+      assert.strictEqual(math.divide(-14n, -5n), 2n)
+      math.config.predictable = false
+   })
+ 
+   it('supports sqrt', () => {
+      assert.strictEqual(math.sqrt(0n), 0n)
+      assert.strictEqual(math.sqrt(4n), 2n)
+      assert.strictEqual(math.sqrt(5n), undefined)
+      assert.strictEqual(
+         math.sqrt(82120471531550314555681345949499512621827274120673745141541602816614526075010755373654280259022317599142038423759320355177481886719814621305828811322920076213800348341464996337890625n),
+         9062034624274524065844376014975805577107171799890766992670739972241112960081909332275390625n)
+      assert.deepStrictEqual(math.sqrt(-9n), math.complex(0n, 3n))
+      assert.deepStrictEqual(
+         math.sqrt(math.complex(5n, 12n)),
+         math.complex(3n, 2n))
+      assert.deepStrictEqual(math.sqrt(math.complex(1n, 0n)), 1n)
+      assert.deepStrictEqual(math.sqrt(math.complex(0n, 1n)), undefined)
+      math.config.predictable = true
+      assert.strictEqual(math.sqrt(-9n), -9n)
+      assert.deepStrictEqual(
+         math.sqrt(math.complex(1n, 0n)), math.complex(1n, 0n))
+      assert.deepStrictEqual(
+         math.sqrt(math.complex(0n, 1n)), math.complex(0n, 0n))
+      assert.deepStrictEqual(
+         math.sqrt(math.complex(0n, 2n)), math.complex(1n, 1n))
+      math.config.predictable = false
+      assert.deepStrictEqual(math.sqrt(-1024n), math.complex(0n, 32n))
+   })
+
+   it('supports sqrt by itself', () => {
+      const bo = new PocomathInstance('BigInts Only')
+      bo.install(bigintSqrt)
+      assert.strictEqual(bo.sqrt(256n), 16n)
+      assert.strictEqual(bo.sqrt(-17n), undefined)
+      bo.install(complex)
+      bo.install(bigints)
+      assert.deepStrictEqual(bo.sqrt(-3249n), bo.complex(0n, 57n))
+   })
+
+})
diff --git a/test/complex/_all.mjs b/test/complex/_all.mjs
index 9d09222..1d49855 100644
--- a/test/complex/_all.mjs
+++ b/test/complex/_all.mjs
@@ -9,6 +9,9 @@ describe('complex', () => {
       assert.deepStrictEqual(
          math.sqrt(math.complex(0,1)),
          math.complex(math.sqrt(0.5), math.sqrt(0.5)))
+      assert.deepStrictEqual(
+         math.sqrt(math.complex(5, 12)),
+         math.complex(3, 2))
       math.config.predictable = true
       assert.deepStrictEqual(math.sqrt(math.complex(1,0)), math.complex(1,0))
       assert.deepStrictEqual(
diff --git a/test/custom.mjs b/test/custom.mjs
index 4df9d67..e057dbf 100644
--- a/test/custom.mjs
+++ b/test/custom.mjs
@@ -23,7 +23,7 @@ describe('A custom instance', () => {
 
    it("can be assembled in any order", () => {
       bw.install(numbers)
-      bw.install({Types: {string: {test: s => typeof s === 'string'}}})
+      bw.install({Type_string: {test: s => typeof s === 'string'}})
       assert.strictEqual(bw.subtract(16, bw.add(3,4,2)), 7)
       assert.strictEqual(bw.negate('8'), -8)
       assert.deepStrictEqual(bw.add(bw.complex(1,3), 1), {re: 2, im: 3})
diff --git a/test/number/_all.mjs b/test/number/_all.mjs
index b334fef..1af4ed4 100644
--- a/test/number/_all.mjs
+++ b/test/number/_all.mjs
@@ -4,6 +4,7 @@ import PocomathInstance from '../../src/core/PocomathInstance.mjs'
 import * as numberSqrt from '../../src/number/sqrt.mjs'
 import * as complex from '../../src/complex/all.mjs'
 import * as numbers from '../../src/number/all.mjs'
+
 describe('number', () => {
    it('supports sqrt', () => {
       assert.strictEqual(math.sqrt(4), 2)