diff --git a/src/bigint/all.mjs b/src/bigint/all.mjs
index f9da9f0..6f1412d 100644
--- a/src/bigint/all.mjs
+++ b/src/bigint/all.mjs
@@ -1,6 +1,6 @@
 import PocomathInstance from '../core/PocomathInstance.mjs'
 import * as bigints from './native.mjs'
 import * as generic from '../generic/all.mjs'
-import * as floor from '../ops/floor.mjs'
+import * as ops from '../ops/all.mjs'
 
-export default PocomathInstance.merge('bigint', bigints, generic, floor)
+export default PocomathInstance.merge('bigint', bigints, generic, ops)
diff --git a/src/core/PocomathInstance.mjs b/src/core/PocomathInstance.mjs
index c1cee4a..6fab6c9 100644
--- a/src/core/PocomathInstance.mjs
+++ b/src/core/PocomathInstance.mjs
@@ -66,6 +66,7 @@ export default class PocomathInstance {
             return true // successful
          }
       })
+      this._plainFunctions = new Set() // the names of the plain functions
       this._chainRepository = {} // place to store chainified functions
    }
 
@@ -136,6 +137,8 @@ export default class PocomathInstance {
       for (const [item, spec] of Object.entries(ops)) {
          if (spec instanceof PocomathInstance) {
             this._installInstance(spec)
+         } else if (typeof spec === 'function') {
+            stdFunctions[item] = spec
          } else {
             if (item.charAt(0) === '_') {
                throw new SyntaxError(
@@ -183,6 +186,9 @@ export default class PocomathInstance {
             migrateImps[operator] = other._imps[operator]
          }
       }
+      for (const plain of other._plainFunctions) {
+         migrateImps[plain] = other[plain]
+      }
       this._installFunctions(migrateImps)
    }
 
@@ -352,7 +358,21 @@ export default class PocomathInstance {
    /* Used internally by install, see the documentation there */
    _installFunctions(functions) {
       for (const [name, spec] of Object.entries(functions)) {
-         // new implementations, so set the op up to lazily recreate itself
+         if (typeof spec === 'function') {
+            if (name in this) {
+               if (spec === this[name]) continue
+               throw new SyntaxError(`Attempt to redefine function ${name}`)
+            }
+            this._plainFunctions.add(name)
+            this[name] = spec
+            continue
+         }
+         // new implementations, first check the name isn't taken
+         if (this._plainFunctions.has(name)) {
+            throw new SyntaxError(
+               `Can't add implementations to function ${name}`)
+         }
+         // All clear, so set the op up to lazily recreate itself
          this._invalidate(name)
          const opImps = this._imps[name]
          for (const [signature, behavior] of Object.entries(spec)) {
diff --git a/src/number/all.mjs b/src/number/all.mjs
index bedaa24..622484a 100644
--- a/src/number/all.mjs
+++ b/src/number/all.mjs
@@ -1,7 +1,7 @@
 import PocomathInstance from '../core/PocomathInstance.mjs'
 import * as numbers from './native.mjs'
 import * as generic from '../generic/all.mjs'
-import * as floor from '../ops/floor.mjs'
+import * as ops from '../ops/all.mjs'
 
-export default PocomathInstance.merge('number', numbers, generic, floor)
+export default PocomathInstance.merge('number', numbers, generic, ops)
 
diff --git a/src/ops/all.mjs b/src/ops/all.mjs
new file mode 100644
index 0000000..3d1646b
--- /dev/null
+++ b/src/ops/all.mjs
@@ -0,0 +1,4 @@
+export * from './choose.mjs'
+export * from './factorial.mjs'
+export * from './floor.mjs'
+
diff --git a/src/ops/choose.mjs b/src/ops/choose.mjs
new file mode 100644
index 0000000..c285dc7
--- /dev/null
+++ b/src/ops/choose.mjs
@@ -0,0 +1,11 @@
+/* Note this is not a good algorithm for computing binomial coefficients,
+ * it's just for demonstration purposes
+ */
+export const choose = {
+   'NumInt,NumInt': ({factorial}) => (n,k) => Number(
+      factorial(n) / (factorial(k)*factorial(n-k))),
+   'bigint,bigint': ({
+      factorial
+   }) => (n,k) => factorial(n) / (factorial(k)*factorial(n-k))
+}
+        
diff --git a/src/ops/factorial.mjs b/src/ops/factorial.mjs
new file mode 100644
index 0000000..bb07047
--- /dev/null
+++ b/src/ops/factorial.mjs
@@ -0,0 +1,8 @@
+export function factorial(n) {
+   n = BigInt(n)
+   let prod = 1n
+   for (let i = n; i > 1n; --i) {
+      prod *= i
+   }
+   return prod
+}
diff --git a/src/pocomath.mjs b/src/pocomath.mjs
index cb9bf94..dee980e 100644
--- a/src/pocomath.mjs
+++ b/src/pocomath.mjs
@@ -4,9 +4,9 @@ import * as numbers from './number/native.mjs'
 import * as bigints from './bigint/native.mjs'
 import * as complex from './complex/native.mjs'
 import * as generic from './generic/all.mjs'
-import * as floor from './ops/floor.mjs'
+import * as ops from './ops/all.mjs'
 
 const math = PocomathInstance.merge(
-    'math', numbers, bigints, complex, generic, floor)
+    'math', numbers, bigints, complex, generic, ops)
 
 export default math
diff --git a/test/_pocomath.mjs b/test/_pocomath.mjs
index 222fbd6..18643b0 100644
--- a/test/_pocomath.mjs
+++ b/test/_pocomath.mjs
@@ -93,4 +93,14 @@ describe('The default full pocomath instance "math"', () => {
       assert.throws(() => math.chain(3).foo(), /Unknown operation/)
    })
 
+   it('calls plain factorial function', () => {
+      assert.strictEqual(math.factorial(4), 24n)
+      assert.strictEqual(math.factorial(7n), 5040n)
+   })
+
+   it('calculates binomial coefficients', () => {
+      assert.strictEqual(math.choose(6, 3), 20)
+      assert.strictEqual(math.choose(21n, 2n), 210n)
+   })
+
 })