complex/extendToComplex.mjs

@@ -0,0 +1,19 @@
+import './Complex.mjs'
+import * as complex from './complex.mjs'
+
+/* Add all the complex implementations for functions already
+   in the instance:
+*/
+
+export default async function extendToComplex(pmath) {
+   pmath.install(complex)
+   for (const name in pmath._imps) {
+      const modulePath = `./${name}.mjs`
+      try {
+         const mod = await import(modulePath)
+         pmath.install(mod)
+      } catch (err) {
+         // Guess it wasn't a method available in complex; no worries
+      }
+   }
+}

test/custom.mjs

@@ -3,9 +3,11 @@ import math from '../pocomath.mjs'
 import typed from 'typed-function'
 import PocomathInstance from '../PocomathInstance.mjs'
 import * as numbers from '../number/all.mjs'
+import * as numberAdd from '../number/add.mjs'
 import * as complex from '../complex/all.mjs'
 import * as complexAdd from '../complex/add.mjs'
 import * as complexNegate from '../complex/negate.mjs'
+import extendToComplex from '../complex/extendToComplex.mjs'
 
 const bw = new PocomathInstance('backwards')
 describe('A custom instance', () => {
@@ -38,4 +40,18 @@ describe('A custom instance', () => {
       assert.deepStrictEqual(
          pm.subtract({re:5, im:0}, {re:10, im:1}), {re:-5, im: -1})
    })
+
+   it("can selectively import in cute ways", async function () {
+      const cherry = new PocomathInstance('cherry')
+      cherry.install(numberAdd)
+      await extendToComplex(cherry)
+      // Now we have an instance that supports addition for number and complex
+      // and little else:
+      assert.strictEqual(cherry.add(3, 4, 2), 9)
+      assert.deepStrictEqual(
+         cherry.add(cherry.complex(3, 3), 4, cherry.complex(2, 2)),
+         math.complex(9,5))
+      assert.strictEqual('subtract' in cherry, false)
+      assert.strictEqual('negate' in cherry, false)
+   })
 })