125 lines
3.5 KiB
TypeScript
125 lines
3.5 KiB
TypeScript
import { TokenType, Token, Group, Item, Items } from './tokens.js';
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import { Scanner } from './scanner.js';
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function matchingParen(c: string): string | null {
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switch (c) {
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case ')': return '(';
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case ']': return '[';
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case '}': return '{';
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default: return null;
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}
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}
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export class LaxReader implements IterableIterator<Item> {
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readonly scanner: Scanner;
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readonly stack: Array<Group> = [];
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constructor(scanner: Scanner) {
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this.scanner = scanner;
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}
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[Symbol.iterator](): IterableIterator<Item> {
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return this;
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}
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stackTop(): Group | null {
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return this.stack[this.stack.length - 1] ?? null;
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}
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popUntilMatch(t: Token): Group | 'continue' | 'eof' {
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const m = matchingParen(t.text);
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if (m !== null && !this.stack.some(g => g.start.text === m)) {
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if (this.stack.length > 0) {
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this.stackTop()!.items.push(t);
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return 'continue';
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}
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} else {
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while (this.stack.length > 0) {
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const inner = this.stack.pop()!;
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if (inner.start.text === m) {
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inner.end = t;
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}
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if (this.stack.length === 0) {
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return inner;
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} else {
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const outer = this.stackTop()!;
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outer.items.push(inner);
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if (inner.start.text === m) {
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return 'continue';
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}
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}
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}
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}
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return 'eof';
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}
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peek(): Token {
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return this.scanner.peek() ?? this.scanner.makeToken(this.scanner.mark(), TokenType.CLOSE, '');
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}
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drop() {
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this.scanner.drop();
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}
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read(): Item | null {
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while (true) {
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let g = this.stackTop();
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const t = this.peek();
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switch (t.type) {
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case TokenType.SPACE:
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case TokenType.NEWLINE:
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case TokenType.ATOM:
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case TokenType.STRING:
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if (g === null) {
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this.drop();
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return t;
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}
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if (t.text === ';') {
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while ('(['.indexOf(g.start.text) >= 0) {
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this.stack.pop();
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const outer = this.stackTop();
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if (outer === null) {
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// do not drop the semicolon here
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return g;
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}
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outer.items.push(g);
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g = outer;
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}
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}
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this.drop();
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g.items.push(t);
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break;
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case TokenType.OPEN:
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this.drop();
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this.stack.push({ start: t, end: null, items: [] });
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break;
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case TokenType.CLOSE: {
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this.drop();
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const i = this.popUntilMatch(t);
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if (i === 'eof') return null;
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if (i === 'continue') break;
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return i;
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}
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}
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}
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}
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readToEnd(): Items {
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return Array.from(this);
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}
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next(): IteratorResult<Item> {
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const i = this.read();
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if (i === null) {
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return { done: true, value: null };
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} else {
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return { done: false, value: i };
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}
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}
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}
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