feat: Initial core of picomath

Implements a totally simplistic "poortf" mutable typed function and
  a picomath instance generator, as well as the very beginnings of a
  number type and one generic function and a default full picomath instance.

  Also provides some tests which serve as usage examples.

test/_picomath.js

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+import assert from 'assert'
+import math from '../picomath.js'
+
+describe('The default full picomath instance "math"', () => {
+   it('performs basic arithmetic operations', () => {
+      assert.strictEqual(math.subtract(16, math.add(3,4,2)), 7)
+      assert.strictEqual(math.negate(math.number('8')), -8)
+   })
+
+   it('can be extended', () => {
+      math('add', [args => typeof args[0] === 'string',
+         (...addends) => addends.reduce((x,y) => x+y, '')])
+      assert.strictEqual(math.add('Kilroy',' is here'), 'Kilroy is here')
+   })
+})

test/_picomathInstance.js

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+import assert from 'assert'
+import picomathInstance from '../picomathInstance.js'
+
+describe('picomath core', () => {
+   it('creates an instance that can define TFs', () => {
+      const pmath = picomathInstance('pmath')
+      pmath('add', [() => true, (a,b) => a+b])
+      assert.strictEqual(pmath.add(2,2), 4)
+      assert.strictEqual(pmath.add('Kilroy', 17), 'Kilroy17')
+      assert.strictEqual(pmath.add(1), NaN)
+      // I guess + never throws!
+   })
+})

test/_poortf.js

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+import assert from 'assert'
+import poortf from '../poortf.js'
+
+describe('poortf', () => {
+   const slate = poortf('slate')
+   it('creates an empty tf', () => {
+      assert.throws(() => slate('empty'), TypeError)
+      assert.throws(() => slate('empty'), /slate.*empty/)
+   })
+
+   const add = poortf('add', [
+      [args => Array.from(args).every(a => typeof a === 'number'),
+       (a, b) => a+b],
+      [args => Array.from(args).every(a => typeof a === 'boolean'),
+       (p, q) => p || q]
+   ])
+   
+   it('creates a tf with initial behaviors', () => {
+      assert.strictEqual(add(2,2), 4)
+      assert.strictEqual(add(true, false), true)
+      assert.throws(() => add('kilroy'), TypeError)
+   })
+
+   it('extends an empty tf', () => {
+      slate.addImps([
+         [args => typeof args[0] === 'string', s => s + ' wuz here'],
+         [args => typeof args[0] === 'number', () => 'I am not a number']
+      ])
+      assert.strictEqual(slate('Kilroy', 'was here'), 'Kilroy wuz here')
+      assert.strictEqual(slate(2, 'was here'), 'I am not a number')
+      assert.throws(() => slate(['Ha!']), TypeError)
+   })
+
+   it('extends a tf with other behaviors', () => {
+      add.addImps([args => typeof args[0] === 'string', (s,x) => s + x]),
+      assert.strictEqual(add('Kilroy', 23), 'Kilroy23')
+      assert.throws(() => add(['Ha!'], 'gotcha'), TypeError)
+   })
+})
+      
+