50 lines
1.2 KiB
TypeScript
50 lines
1.2 KiB
TypeScript
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export class Lexer {
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str: string;
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pos: number;
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constructor(str: string) {
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this.str = str;
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this.pos = 0;
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}
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next(): string {
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return this.str[this.pos++];
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}
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peek(): string {
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return this.str[this.pos];
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}
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match(str: string): boolean {
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if (this.str.slice(this.pos, this.pos + str.length) === str) {
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this.pos += str.length;
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return true;
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}
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return false;
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}
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matchDigit(): string {
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if (/\d/.test(this.peek())) {
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return this.next();
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}
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return "";
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}
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skipN(n: number) {
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this.pos += n;
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}
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matchDigitN(min: number, max: number) {
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const originalPos = this.pos;
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let digits = "";
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for (let i = 0; i < min; i++) {
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if (!/\d/.test(this.peek())) {
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this.pos = originalPos;
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return false;
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}
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digits += this.next();
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}
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for (let i = 0; i < max - min; i++) {
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if (!/\d/.test(this.peek())) {
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break;
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}
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digits += this.next();
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}
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return digits;
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}
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}
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