66 lines
1.3 KiB
V
66 lines
1.3 KiB
V
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module math
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import math.internal
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fn poly_n_eval(c []f64, n int, x f64) f64 {
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if c.len == 0 {
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panic('coeficients can not be empty')
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}
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len := int(min(c.len, n))
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mut ans := c[len - 1]
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for e in c[..len - 1] {
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ans = e + x * ans
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}
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return ans
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}
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fn poly_n_1_eval(c []f64, n int, x f64) f64 {
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if c.len == 0 {
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panic('coeficients can not be empty')
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}
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len := int(min(c.len, n)) - 1
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mut ans := c[len - 1]
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for e in c[..len - 1] {
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ans = e + x * ans
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}
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return ans
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}
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[inline]
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fn poly_eval(c []f64, x f64) f64 {
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return poly_n_eval(c, c.len, x)
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}
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[inline]
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fn poly_1_eval(c []f64, x f64) f64 {
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return poly_n_1_eval(c, c.len, x)
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}
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// data for a Chebyshev series over a given interval
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struct ChebSeries {
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pub:
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c []f64 // coefficients
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order int // order of expansion
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a f64 // lower interval point
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b f64 // upper interval point
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}
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fn (cs ChebSeries) eval_e(x f64) (f64, f64) {
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mut d := 0.0
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mut dd := 0.0
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y := (2.0 * x - cs.a - cs.b) / (cs.b - cs.a)
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y2 := 2.0 * y
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mut e_ := 0.0
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mut temp := 0.0
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for j := cs.order; j >= 1; j-- {
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temp = d
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d = y2 * d - dd + cs.c[j]
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e_ += abs(y2 * temp) + abs(dd) + abs(cs.c[j])
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dd = temp
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}
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temp = d
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d = y * d - dd + 0.5 * cs.c[0]
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e_ += abs(y * temp) + abs(dd) + 0.5 * abs(cs.c[0])
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return d, f64(internal.f64_epsilon) * e_ + abs(cs.c[cs.order])
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}
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