112 lines
4.0 KiB
JavaScript
112 lines
4.0 KiB
JavaScript
/* Core of pocomath: create an instance */
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import typed from 'typed-function'
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export default class PocomathInstance {
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constructor(name) {
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this.name = name
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this._imps = {}
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}
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/**
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* (Partially) define one or more operations of the instance:
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*
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* @param {Object<string, Object<Signature, [string[], function]>>} ops
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* The only parameter ops gives the semantics of the operations to install.
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* The keys are operation names. The value for a key is an object
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* mapping (typed-function) signature strings to pairs of dependency
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* lists and implementation functions.
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*
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* A dependency list is a list of strings. Each string can either be the
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* name of a function that the corresponding implementation has to call,
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* or a specification of a particular signature of a function that it has
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* to call, in the form 'FN(SIGNATURE)'. Note the function name can be
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* the special value 'self' to indicate a recursive call to the given
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* operation (either with or without a particular signature.
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*
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* There are two cases for the implementation function. If the dependency
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* list is empty, it should be a function taking the arguments specified
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* by the signature and returning the value. Otherwise, it should be
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* a function taking an object with the dependency lists as keys and the
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* requested functions as values, to a function taking the arguments
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* specified by the signature and returning the value
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*/
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install(ops) {
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for (const key in ops) this._installOp(key, ops[key])
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}
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/* Used internally by install, see the documentation there */
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_installOp(name, implementations) {
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// new implementations, so set the op up to lazily recreate itself
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this._invalidate(name)
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const opImps = this._imps[name]
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for (const signature in implementations) {
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if (signature in opImps) {
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if (implemenatations[signature] === opImps[signature]) continue
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throw new SyntaxError(
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`Conflicting definitions of ${signature} for ${name}`)
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} else {
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opImps[signature] = implementations[signature]
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}
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}
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}
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/**
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* Reset an operation to require creation of typed-function,
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* and if it has no implementations so far, set them up.
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*/
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_invalidate(name) {
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const self = this
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this[name] = function () {
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return self._bundle(name).apply(self, arguments)
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}
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if (!(name in this._imps)) {
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this._imps[name] = {}
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}
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}
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/**
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* Create a typed-function from the signatures for the given name and
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* assign it to the property with that name, returning it as well
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*/
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_bundle(name) {
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const imps = this._imps[name]
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if (!imps || Object.keys(imps).length === 0) {
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throw new SyntaxError(`No implementations for ${name}`)
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}
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const tf_imps = {}
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for (const signature in imps) {
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const [deps, imp] = imps[signature]
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if (deps.length === 0) {
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tf_imps[signature] = imp
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} else {
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const refs = {}
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for (const dep of deps) {
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// TODO: handle self dependencies
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if (dep.slice(0,4) === 'self') {
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throw new Error('self-reference unimplemented')
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}
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// TODO: handle signature-specific dependencies
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if (dep.includes('(')) {
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throw new Error('signature specific reference unimplemented')
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}
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refs[dep] = this._ensureBundle(dep) // just assume acyclic for now
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}
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tf_imps[signature] = imp(refs)
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}
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}
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const tf = typed(name, tf_imps)
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this[name] = tf
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return tf
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}
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/**
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* Ensure that the generated typed function is assigned to the given
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* name and return it
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*/
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_ensureBundle(name) {
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const maybe = this[name]
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if (typed.isTypedFunction(maybe)) return maybe
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return this._bundle(name)
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}
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}
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