src/Loc.js

/** Represents a single location in the source string. */
export class Pos {
	constructor(line /* Number */, column /* Number */) {
		this.line = line
		this.column = column
	}

	/** Advance the pos by any character. */
	next(ch) {
		return ch === '\n' ? this.onNextLine() : this.onNextColumn()
	}

	/** Poc after a newline. */
	onNextLine() {
		return new Pos(this.line + 1, StartColumn)
	}

	/** Loc after a non-newline character. */
	onNextColumn() {
		return new Pos(this.line, this.column + 1)
	}

	/**
	 * Undoes {@link onNextLine}.
	 * Only call this is you know this is not the first column.
	 */
	onPrevColumn() {
		return new Pos(this.line, this.column - 1)
	}

	/** @override */
	toString() {
		return `${this.line}:${this.column}`
	}
}

/** Range of text in the source string. */
export default class Loc {
	constructor(start /* Pos */, end /* Pos */) {
		this.start = start
		/** Beginning of text. */
		this.end = end
		/** End of text. */
	}

	/** @override */
	toString() {
		return `${this.start}-${this.end}`
	}
}

/**
Loc consisting of the character at `pos`.
@param {Pos} pos
*/
export function singleCharLoc(pos) {
	return new Loc(pos, pos.next('x'))
}

/** First line number for a source string; they start at 1. */
export const StartLine = 1

/** Fist column number for a line; they start at 0. */
export const StartColumn = 0

/** First {@link Pos} in a source string. */
export const StartPos = new Pos(StartLine, StartColumn)