https://github.com/Sajjon/EquationKit
Write equations in pure Swift, differentiate and/or evaluate them.
let polynomial = (3*x + 5*y - 17) * (7*x - 9*y + 23)
print(polynomial) // 21x² + 8xy - 50x - 45y² + 268y - 391)
let number = polynomial.evaluate() {[ x <- 4, y <- 1 ]}
print(number) // 0
let y＇ = equation.differentiateWithRespectTo(x)
print(y＇) // 42x + 8y - 50
y＇.evaluate() {[ x <- 1, y <- 1 ]} // 0
let x＇ = equation.differentiateWithRespectTo(y)
print(x＇) // 8x - 90y + 268
x＇.evaluate() {[ x <- 11.5, y <- 4 ]} // 0