Steffensen's method: Difference between revisions
Added Go
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Line 468:
t0 = 0.9 : intersection at (-0.681025, 2.681025)
t0 = 1.0 : no answer</pre>
=={{header|Go}}==
{{trans|C}}
<syntaxhighlight lang="go">package main
import (
"fmt"
"math"
)
type fun = func(float64) float64
func aitken(f fun, p0 float64) float64 {
p1 := f(p0)
p2 := f(p1)
p1m0 := p1 - p0
return p0 - p1m0*p1m0/(p2-2.0*p1+p0)
}
func steffensenAitken(f fun, pinit, tol float64, maxiter int) float64 {
p0 := pinit
p := aitken(f, p0)
iter := 1
for math.Abs(p-p0) > tol && iter < maxiter {
p0 = p
p = aitken(f, p0)
iter++
}
if math.Abs(p-p0) > tol {
return math.NaN()
}
return p
}
func deCasteljau(c0, c1, c2, t float64) float64 {
s := 1.0 - t
c01 := s*c0 + t*c1
c12 := s*c1 + t*c2
return s*c01 + t*c12
}
func xConvexLeftParabola(t float64) float64 {
return deCasteljau(2.0, -8.0, 2.0, t)
}
func yConvexRightParabola(t float64) float64 {
return deCasteljau(1.0, 2.0, 3.0, t)
}
func implicitEquation(x, y float64) float64 {
return 5.0*x*x + y - 5.0
}
func f(t float64) float64 {
x := xConvexLeftParabola(t)
y := yConvexRightParabola(t)
return implicitEquation(x, y) + t
}
func main() {
t0 := 0.0
for i := 0; i < 11; i++ {
fmt.Printf("t0 = %0.1f : ", t0)
t := steffensenAitken(f, t0, 0.00000001, 1000)
if math.IsNaN(t) {
fmt.Println("no answer")
} else {
x := xConvexLeftParabola(t)
y := yConvexRightParabola(t)
if math.Abs(implicitEquation(x, y)) <= 0.000001 {
fmt.Printf("intersection at (%f, %f)\n", x, y)
} else {
fmt.Println("spurious solution")
}
}
t0 += 0.1
}
}</syntaxhighlight>
{{out}}
<pre>
Same as C example
</pre>
=={{header|RATFOR}}==
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