Circles of given radius through two points: Difference between revisions
Circles of given radius through two points (view source)
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Points (0.1234,0.9876), (0.1234,0.9876) Radius 0.0000.
Points are coincident.
</pre>
=={{header|Vlang}}==
{{trans|Go}}
<lang vlang>import math
const (
two = "two circles."
r0 = "R==0.0 does not describe circles."
co = "coincident points describe an infinite number of circles."
cor0 = "coincident points with r==0.0 describe a degenerate circle."
diam = "Points form a diameter and describe only a single circle."
far = "Points too far apart to form circles."
)
struct Point {
x f64
y f64
}
fn circles(p1 Point, p2 Point, r f64) (Point, Point, string) {
mut case := ''
c1, c2 := p1, p2
if p1 == p2 {
if r == 0 {
return p1, p1, cor0
}
case = co
return c1, c2, case
}
if r == 0 {
return p1, p2, r0
}
dx := p2.x - p1.x
dy := p2.y - p1.y
q := math.hypot(dx, dy)
if q > 2*r {
case = far
return c1, c2, case
}
m := Point{(p1.x + p2.x) / 2, (p1.y + p2.y) / 2}
if q == 2*r {
return m, m, diam
}
d := math.sqrt(r*r - q*q/4)
ox := d * dx / q
oy := d * dy / q
return Point{m.x - oy, m.y + ox}, Point{m.x + oy, m.y - ox}, two
}
struct Cir {
p1 Point
p2 Point
r f64
}
const td = [
Cir{Point{0.1234, 0.9876}, Point{0.8765, 0.2345}, 2.0},
Cir{Point{0.0000, 2.0000}, Point{0.0000, 0.0000}, 1.0},
Cir{Point{0.1234, 0.9876}, Point{0.1234, 0.9876}, 2.0},
Cir{Point{0.1234, 0.9876}, Point{0.8765, 0.2345}, 0.5},
Cir{Point{0.1234, 0.9876}, Point{0.1234, 0.9876}, 0.0},
]
fn main() {
for tc in td {
println("p1: $tc.p1")
println("p2: $tc.p2")
println("r: $tc.r")
c1, c2, case := circles(tc.p1, tc.p2, tc.r)
println(" $case")
match case {
cor0, diam{
println(" Center: $c1")
}
two {
println(" Center 1: $c1")
println(" Center 2: $c2")
}
else{}
}
println('')
}
}</lang>
{{out}}
<pre>
p1: Point{
x: 0.1234
y: 0.9876
}
p2: Point{
x: 0.8765
y: 0.2345
}
r: 2
two circles.
Center 1: Point{
x: 1.863111801658189
y: 1.9742118016581887
}
Center 2: Point{
x: -0.8632118016581891
y: -0.7521118016581888
}
p1: Point{
x: 0
y: 2
}
p2: Point{
x: 0
y: 0
}
r: 1
Points form a diameter and describe only a single circle.
Center: Point{
x: 0
y: 1
}
p1: Point{
x: 0.1234
y: 0.9876
}
p2: Point{
x: 0.1234
y: 0.9876
}
r: 2
coincident points describe an infinite number of circles.
p1: Point{
x: 0.1234
y: 0.9876
}
p2: Point{
x: 0.8765
y: 0.2345
}
r: 0.5
Points too far apart to form circles.
p1: Point{
x: 0.1234
y: 0.9876
}
p2: Point{
x: 0.1234
y: 0.9876
}
r: 0
coincident points with r==0.0 describe a degenerate circle.
Center: Point{
x: 0.1234
y: 0.9876
}
</pre>
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