identity.hhs

/**
 * @author Mudroad White
 * @param input - a positive integer denoting the size of the expected matrix.
 * @returns - a Mat object representing a 2D identity matrix.
 */

function identity(input) {

	*import math: is_number

	// Corner cases for input
	// Argument length should be only one
	if ( !(arguments.length === 1) ) {
    	throw new Error('Identity expects only one argument');
	}
	// Input should be a positive integer
	if (!Number.isInteger(input) || input < 0) {
		throw new Error('Excepted positive integer input');
	}

	// Then we return special Mat value when input is 0 or 1
	if (input === 0) {
		return new Mat([]);
	}

	if (input === 1) {
		return new Mat([[1]]);
	}

	// Now we can start on creating the Id matrix
	let result = new Mat().zeros(input, input);
	for (let i = 0; i < input; i++){
		result.val[i][i] = 1;
	}	

	// return as a Mat object
	return result;
}