slige/src/Lexer.ts

import { Pos, Token } from "./Token.ts";

class Lexer {
    private index = 0;
    private line = 1;
    private col = 1;


    public constructor (private text: string) {}

    public next(): Token | null { return null }
    
    private done(): boolean { return this.index >= this.text.length; }
    private current(): string { return this.text[this.index]; }

    private step() {
        if (this.done())
            return;
        if (this.current() === "\n") {
            this.line += 1;
            this.col = 1;
        } else {
            this.col += 1;
        }
        this.index += 1;
    }

    private pos(): Pos {
        return {
            index: this.index,
            line: this.line,
            col: this.col
        }
    }

    private token(type: string, pos: Pos): Token {
        const length = this.index - pos.index;
        return { type, pos, length };
    }
}