Data commit

Task/Elliptic-curve-arithmetic/Kotlin/elliptic-curve-arithmetic.kotlin

@@ -0,0 +1,58 @@
+// version 1.1.4
+
+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}")
+}