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feat: Implement subtypes

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This should eventually be moved into typed-function itself, but for
  now it can be implemented on top of the existing typed-function.

  Uses subtypes to define (and error-check) gcd and lcm, which are only
  defined for integer arguments.

  Resolves #36.
This commit is contained in:
Glen Whitney 2022-07-30 04:59:04 -07:00
parent 4d38f4161c
commit c429c19dfe
35 changed files with 294 additions and 43 deletions
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65
src/core/PocomathInstance.mjs
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@ -27,6 +27,7 @@ export default class PocomathInstance {
this._typed = typed.create()
this._typed.clear()
this.Types = {any: anySpec} // dummy entry to track the default 'any' type
this._subtypes = {} // For each type, gives all of its (in)direct subtypes
this._usedTypes = new Set() // all types that have occurred in a signature
this._doomed = new Set() // for detecting circular reference
this._config = {predictable: false}
@ -190,6 +191,9 @@ export default class PocomathInstance {
* **to** this type to the corresponding conversion functions
* - before: [optional] a list of types this should be added
* before, in priority order
* - refines: [optional] the name of a type that this is a subtype
* of. This means the test is the conjunction of the given test and
* the supertype test, and that it must come before the supertype.
*/
/*
* Implementation note: unlike _installFunctions below, we can make
@ -202,29 +206,68 @@ export default class PocomathInstance {
}
return
}
let beforeType = 'any'
for (const other of spec.before || []) {
if (other in this.Types) {
beforeType = other
break
if (spec.refines && !(spec.refines in this.Types)) {
throw new SyntaxError(
`Cannot install ${type} before its supertype ${spec.refines}`)
}
let beforeType = spec.refines
if (!beforeType) {
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)
let testFn = spec.test
if (spec.refines) {
const supertypeTest = this.Types[spec.refines].test
testFn = entity => supertypeTest(entity) && spec.test(entity)
}
this._typed.addTypes([{name: type, test: testFn}], beforeType)
this.Types[type] = spec
/* 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]})
// add conversions from "from" to this one and all its supertypes:
let nextSuper = type
while (nextSuper) {
this._typed.addConversion(
{from, to: nextSuper, convert: spec.from[from]})
nextSuper = this.Types[nextSuper].refines
}
}
}
/* 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]})
if (spec.refines == to || spec.refines in this._subtypes[to]) {
throw new SyntaxError(
`Conversion of ${type} to its supertype ${to} disallowed.`)
}
let nextSuper = to
while (nextSuper) {
this._typed.addConversion({
from: type,
to: nextSuper,
convert: this.Types[to].from[type]
})
nextSuper = this.Types[nextSuper].refines
}
}
}
this.Types[type] = spec
if (spec.refines) {
this._typed.addConversion(
{from: type, to: spec.refines, convert: x => x})
}
this._subtypes[type] = new Set()
// Update all the subtype sets of supertypes up the chain:
let nextSuper = spec.refines
while (nextSuper) {
this._subtypes[nextSuper].add(type)
nextSuper = this.Types[nextSuper].refines
}
// rebundle anything that uses the new type:
this._invalidateDependents(':' + type)
}