#!/usr/bin/ruby

func chebft1 (callback, a, b, n) {

    var bma = (b-a)/2
    var bpa = (b+a)/2

    var pi_n = (@^n  |>> (:add, 0.5) |>> (:mul, Num.pi / n))
    var f    = (pi_n |>> :cos |>> (:mul, bma) |>> (:add, bpa) |>> callback)
    var sums = (@^n  |>> {|i| pi_n |>> (:mul, i) |>> :cos ~Z* f |> :sum })

    sums |>> (:mul, 2/n)
}

func chebft2 (callback, a, b, n) {

    var bma = (0.5 * b-a)
    var bpa = (0.5 * b+a)

    var pi_n = ((@^n Â»+Â» 0.5) Â»*Â» (Num.pi / n))
    var f    = (pi_n Â»cosÂ»() Â»*Â» bma Â»+Â» bpa Â«callÂ« callback)
    var sums = (@^n Â«runÂ« {|i| f Â»*Â« ((pi_n Â»*Â» i) Â»cosÂ»()) Â«+Â» })

    sums Â»*Â» 2/n
}

assert_eq(
    chebft1(func(v){v.cos}, 0, 1, 10).map{ .round(-40) }
    chebft2(func(v){v.cos}, 0, 1, 10).map{ .round(-40) }
)

say "** Test passed!"