46 lines
1.4 KiB
JavaScript
46 lines
1.4 KiB
JavaScript
import {Type, Function} from "../metacircular.js";
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import {Int} from "../primitives/symbols.js";
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// Global store of list types:
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const listTypes = new Map();
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export function getListType(elementType) {
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if (listTypes.has(elementType)) {
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// only generate each list type once
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// this would not be necessary if we could define our own equality and hash functions on objects in JavaScript.
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return listTypes.get(elementType);
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}
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else {
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const type = Symbol('ListOf:'+elementType.toString());
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listTypes.set(elementType, type);
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return type;
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}
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}
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export const makeListModule = elementType => {
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// List<elementType> type depends on elementType
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// generating it another time, will give the same type (structurally equivalent):
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const ListOfElement = getListType(elementType);
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const emptyList = {l:[]};
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const get = ls => i => ls.l[i];
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const getBoundType = {in: Int, out: elementType}
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const getType = {in: ListOfElement, out: getBoundType};
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const push = ls => elem => ({l:ls.l.concat([elem])});
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const pushBoundType = {in: elementType, out: ListOfElement};
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const pushType = {in: ListOfElement, out: pushBoundType};
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return [
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{i: ListOfElement, t: Type},
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{i: emptyList , t: ListOfElement},
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{i: get , t: getType},
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{i: getType , t: Function},
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{i: getBoundType , t: Function},
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{i: push , t: pushType},
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{i: pushType , t: Function},
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{i: pushBoundType, t: Function},
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];
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};
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