Reduced Row Echelon Form in Swift

rref.swift

// Int and Double implementation of RREF

func rref(matrix: [[Int]]) -> [[Double]] {
	var lead = 0
	
	var returnMatrix = matrix.map({ (row) in
		return row.map { Double($0) } 
	})
	
	let rowCount = matrix.count
	let columnCount = matrix[0].count
	
	for r in 0..<rowCount {
		if lead >= columnCount { break }
		var x = r
		while returnMatrix[x][lead] == 0 {
			x += 1
			if x == rowCount {
				x = r
				lead += 1
				if columnCount == lead {
					break
				}
			}
		}
		returnMatrix[x][r] = returnMatrix[r][x]
		var lv = returnMatrix[r][lead]
		returnMatrix[r] = returnMatrix[r].map { Double($0) / Double(lv) }
		
		for i in 0..<rowCount {
			if i != r {
				lv = returnMatrix[i][lead]
				returnMatrix[i] = zip(returnMatrix[r], returnMatrix[i]).map {$1 - $0*lv}
			}
		}
		lead += 1
	}
	
	return returnMatrix
}

func rref(matrix: [[Double]]) -> [[Double]] {
	var lead = 0
	
	var returnMatrix = matrix
	
	let rowCount = matrix.count
	let columnCount = matrix[0].count
	
	for r in 0..<rowCount {
		if lead >= columnCount { break }
		var x = r
		while returnMatrix[x][lead] == 0 {
			x += 1
			if x == rowCount {
				x = r
				lead += 1
				if columnCount == lead {
					break
				}
			}
		}
		returnMatrix[x][r] = returnMatrix[r][x]
		var lv = returnMatrix[r][lead]
		returnMatrix[r] = returnMatrix[r].map { Double($0) / Double(lv) }
		
		for i in 0..<rowCount {
			if i != r {
				lv = returnMatrix[i][lead]
				returnMatrix[i] = zip(returnMatrix[r], returnMatrix[i]).map {$1 - $0*lv}
			}
		}
		lead += 1
	}
	
	return returnMatrix
}

// Test: https://www.youtube.com/watch?v=OMHqfaLB1Uo

let mtx = [
	[ 1, 1, 0, 5],
	[ 0, 1, 2, -3],
	[ 3, 0, 1, 10],]


print(rref(matrix: mtx))

// [[1.0, 0.0, 0.0, 4.0], [0.0, 1.0, 0.0, 1.0], [0.0, 0.0, 1.0, -2.0]]

// a = 4
// b = 1
// c = -2