Elliptic curve arithmetic: Difference between revisions

=={{header|Kotlin}}==

{{trans|C}}

<lang scala>// version 1.1.2

const val C = 7

class Pt(val x: Double, val y: Double) {

val zero get() = Pt(Double.POSITIVE_INFINITY, Double.POSITIVE_INFINITY)

val isZero get() = x > 1e20 || x < -1e20

fun dbl(): Pt {

if (isZero) return this

val l = 3.0 * x * x / (2.0 * y)

val t = l * l - 2.0 * x

return Pt(t, l * (x - t) - y)

}

operator fun unaryMinus() = Pt(x, -y)

operator fun plus(other: Pt): Pt {

if (x == other.x && y == other.y) return dbl()

if (isZero) return other

if (other.isZero) return this

val l = (other.y - y) / (other.x - x)

val t = l * l - x - other.x

return Pt(t, l * (x - t) - y)

}

operator fun times(n: Int): Pt {

var r: Pt = zero

var p = this

var i = 1

while (i <= n) {

if ((i and n) != 0) r += p

p = p.dbl()

i = i shl 1

}

return r

}

override fun toString() =

if (isZero) "Zero" else "(${"%.3f".format(x)}, ${"%.3f".format(y)})"

}

fun Double.toPt() = Pt(Math.cbrt(this * this - C), this)

fun main(args: Array<String>) {

val a = 1.0.toPt()

val b = 2.0.toPt()

val c = a + b

val d = -c

println("a = $a")

println("b = $b")

println("c = a + b = $c")

println("d = -c = $d")

println("c + d = ${c + d}")

println("a + b + d = ${a + b + d}")

println("a * 12345 = ${a * 12345}")

}</lang>

{{out}}

<pre>

a = (-1.817, 1.000)

b = (-1.442, 2.000)

c = a + b = (10.375, -33.525)

d = -c = (10.375, 33.525)

c + d = Zero

a + b + d = Zero

a * 12345 = (10.759, 35.387)

</pre>