Roots of a function: Difference between revisions
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(Scala contribution maintained.) |
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=={{header|Scala}}== |
=={{header|Scala}}== |
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===Imperative version (Ugly, side effects)=== |
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{{improve|Scala}}<!-- Why? This template added in place of direct categorization that failed to give any reason. --> |
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{{trans|Java}} |
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{{Out}}Best seen running in your browser either by [https://scalafiddle.io/sf/T63KUsH/0 (ES aka JavaScript, non JVM)] or [https://scastie.scala-lang.org/bh8von94Q1y0tInvEZ3cBQ Scastie (remote JVM)]. |
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<lang Scala>object Roots extends App { |
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val poly = (x: Double) => x * x * x - 3 * x * x + 2 * x |
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private def printRoots(f: Double => Double, |
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lowerBound: Double, |
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upperBound: Double, |
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step: Double): Unit = { |
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val y = f(lowerBound) |
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var (ox, oy, os) = (lowerBound, y, math.signum(y)) |
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for (x <- lowerBound to upperBound by step) { |
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val y = f(x) |
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val s = math.signum(y) |
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if (s == 0) println(x) |
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else if (s != os) println(s"~${x - (x - ox) * (y / (y - oy))}") |
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ox = x |
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oy = y |
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os = s |
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} |
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} |
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printRoots(poly, -1.0, 4, 0.002) |
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}</lang> |
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===Functional version (Recommended)=== |
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<lang Scala>object RootsOfAFunction extends App { |
<lang Scala>object RootsOfAFunction extends App { |
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def findRoots(fn: Double => Double, start: Double, stop: Double, step: Double, epsilon: Double) = { |
def findRoots(fn: Double => Double, start: Double, stop: Double, step: Double, epsilon: Double) = { |
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println(findRoots(fn, -1.0, 3.0, 0.0001, 0.000000001)) |
println(findRoots(fn, -1.0, 3.0, 0.0001, 0.000000001)) |
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}</lang> |
}</lang> |
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{{out}} |
{{out}} |
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Vector(-9.381755897326649E-14, 0.9999999999998124, 1.9999999999997022) |
Vector(-9.381755897326649E-14, 0.9999999999998124, 1.9999999999997022) |
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