pocomath/PocomathInstance.mjs

91 lines
3.3 KiB
JavaScript

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