Here below a little program in Fantom that implements 2 classes (in fact, they are 3 + an extra utility Stopwatch class from my previous post http://carlosqt.blogspot.com/2011/05/stopwatch-class-for-java.html). There is the main class, called Fiborial (Fibo(nnacci)+(Facto)rial) that implements the Fibonacci and the Factorial algorithms in two ways, one Recursive (using recursion) and the other Imperative (using loops and states). The second class is just an instance class that does the same thing, but its there just to show the difference between static and instance classes, and finally the third one (which will not appear in other languages) is the Program class which has the static execution method "main".
You can also find 3 more little examples at the bottom. One prints out the Factorial's Series and Fibonacci's Series, the second one just shows a class that mixes both: static and instance members, and finally the third one that uses different return types (including java.math.BigInteger) for the Factorial method to compare the timing and result.
As with the previous posts, you can copy and paste the code below in your favorite IDE/Editor and start playing and learning with it. This little "working" program will teach you some more basics of the Programming Language.
There are some "comments" on the code added just to tell you what are or how are some features called. In case you want to review the theory, you can read my previous post, where I give a definition of each of the concepts mentioned on the code. You can find it here: http://carlosqt.blogspot.com/2011/01/new-series-factorial-and-fibonacci.html
The Fiborial Program
// Factorial and Fibonacci in Fantom using [java] com.carlosqt.util::Stopwatch using [java] java.math::BigInteger // static is not a valid class modifier // Instanced Class class StaticFiborial { // (Constant) Static Field - Static fields must be const - this ensures thread safety private const static Str className // Class/Static Constructor/Initializer // It is permissible to have multiple static initializers; they run in order of declaration static { className = "Static Constructor" echo(className) } // Static Method - Factorial Recursive static BigInteger factorialR(Int n) { if (n == 1) return BigInteger.ONE else return BigInteger.valueOf(n).multiply(factorialR(n - 1)) } // Static Method - Factorial Imperative static BigInteger factorialI(Int n) { BigInteger res := BigInteger.ONE for (i := n; i >= 1; i--) { res = res.multiply(BigInteger.valueOf(i)) } return res } // Static Method - Fibonacci Recursive static Int fibonacciR(Int n) { if (n < 2) return 1 else return fibonacciR(n - 1) + fibonacciR(n - 2) } // Static Method - Fibonacci Imperative static Int fibonacciI(Int n) { Int pre := 1 Int cur := 1 Int tmp := 0 for (i := 2; i <= n; i++) { tmp = cur + pre pre = cur cur = tmp } return cur } // Class/Static Method - Benchmarking Algorithms static Void benchmarkAlgorithm(Int algorithm, List values) { Stopwatch timer := Stopwatch() Int testValue := 0 BigInteger facTimeResult := BigInteger.ZERO Int fibTimeResult := 0 // "Switch" Flow Control Statement switch (algorithm) { case 1: echo("\nFactorial Imperative:") // "For" Loop Statement for (i := 0; i < values.size; i++) { testValue = values.get(i) // Taking Time timer.start() facTimeResult = factorialI(testValue) timer.stop() // Getting Time echo(" ($testValue) = ${timer.getElapsed()}") } case 2: echo("\nFactorial Recursive:") // "While" Loop Statement Int i := 0 while (i < values.size) { testValue = values.get(i) // Taking Time timer.start() facTimeResult = factorialR(testValue) timer.stop() // Getting Time echo(" ($testValue) = ${timer.getElapsed()}") i++ } case 3: echo("\nFibonacci Imperative:") // "While" Loop Statement Int i := 0 while (i < values.size) { testValue = values.get(i) // Taking Time timer.start() fibTimeResult = fibonacciI(testValue) timer.stop() // Getting Time echo(" ($testValue) = ${timer.getElapsed()}") i++ } case 4: echo("\nFibonacci Recursive:") // "For" Loop Statement for (i := 0; i < values.size; i++) { testValue = values.get(i) // Taking Time timer.start() fibTimeResult = fibonacciR(testValue) timer.stop() // Getting Time echo(" ($testValue) = ${timer.getElapsed()}") } default: echo("DONG!") } } } // Instance Class class InstanceFiborial { // Instance Field private Str className // Instance Constructor new make() { this.className = "Instance Constructor" echo(this.className) } // Instance Method - Factorial Recursive BigInteger factorialR(Int n) { // Calling Static Method return StaticFiborial.factorialR(n) } // Instance Method - Factorial Imperative BigInteger factorialI(Int n) { // Calling Static Method return StaticFiborial.factorialI(n) } // Instance Method - Fibonacci Recursive Int fibonacciR(Int n) { // Calling Static Method return StaticFiborial.fibonacciR(n) } // Instance Method - Factorial Imperative Int fibonacciI(Int n) { // Calling Static Method return StaticFiborial.fibonacciI(n) } } // Console Program public class FiborialApp { public static Void main() { echo("\nStatic Class") // Calling Static Class and Methods // No instantiation needed. Calling method directly from the class echo("FacImp(5) = ${StaticFiborial.factorialI(5)}") echo("FacRec(5) = ${StaticFiborial.factorialR(5)}") echo("FibImp(11)= ${StaticFiborial.fibonacciI(11)}") echo("FibRec(11)= ${StaticFiborial.fibonacciR(11)}") echo("\nInstance Class") // Calling Instance Class and Methods // Need to instantiate before using. Calling method from instantiated object InstanceFiborial ff := InstanceFiborial.make() echo("FacImp(5) = ${ff.factorialI(5)}") echo("FacRec(5) = ${ff.factorialR(5)}") echo("FibImp(11)= ${ff.fibonacciI(11)}") echo("FibRec(11)= ${ff.fibonacciR(11)}") // Create a list of integer values to test // From 5 to 50 by 5 Int[] values := Int[,] for(i := 5; i <= 50; i += 5) values.add(i) // Benchmarking Fibonacci // 1 = Factorial Imperative StaticFiborial.benchmarkAlgorithm(1, values) // 2 = Factorial Recursive StaticFiborial.benchmarkAlgorithm(2, values) // Benchmarking Factorial // 3 = Fibonacci Imperative StaticFiborial.benchmarkAlgorithm(3, values) // 4 = Fibonacci Recursive StaticFiborial.benchmarkAlgorithm(4, values) // Stop and exit echo("Press any key to exit...") console := Env.cur userInput := console.in.readLine } }
And the Output is:
Printing the Factorial and Fibonacci Series
using [java] java.math::BigInteger using [java] java.lang::StringBuffer class Fiborial { // Using a StringBuffer as a list of string elements // because of the following compile error: // Ambiguous call append(sys::Str) FiborialSeries.fan ... Fantom Problem // I had to use StringBuffer.apend(s, 0, s.length) instead of just StringBuffer.apend(CharSequence s) static Str getFactorialSeries(Int n) { // Create the String that will hold the list StringBuffer series := StringBuffer() // We begin by concatenating the number you want to calculate // in the following format: "!# =" series.append("!", 0, "!".size) series.append(n.toStr, 0, n.toStr.size) series.append(" = ", 0, 3) // We iterate backwards through the elements of the series for (i := n; i <= n && i > 0; i--) { // and append it to the list series.append(i.toStr, 0, i.toStr.size) if (i > 1) series.append(" * ", 0, 3) else series.append(" = ", 0, 3) } // Get the result from the Factorial Method // and append it to the end of the list Str fac := factorial(n).toStr series.append(fac, 0, fac.size) // return the list as a string return series.toStr } // Using a StringBuffer as a list of string elements static Str getFibonnaciSeries(Int n) { // Create the String that will hold the list StringBuffer series := StringBuffer() // We begin by concatenating the first 3 values which // are always constant series.append("0, 1, 1", 0, 7) // Then we calculate the Fibonacci of each element // and add append it to the list Str fib := "" for (i := 2; i <= n; i++) { if (i < n) series.append(", ", 0, 2) else series.append(" = ", 0, 3) fib = fibonacci(i).toStr series.append(fib, 0, fib.size) } // return the list as a string return series.toStr } static BigInteger factorial(Int n) { if (n == 1) return BigInteger.ONE else return BigInteger.valueOf(n).multiply(factorial(n - 1)) } static Int fibonacci(Int n) { if (n < 2) return 1 else return fibonacci(n - 1) + fibonacci(n - 2) } } // Console Program public class FiborialSeriesApp { public static Void main() { // Printing Factorial Series echo("") echo(Fiborial.getFactorialSeries(5)) echo(Fiborial.getFactorialSeries(7)) echo(Fiborial.getFactorialSeries(9)) echo(Fiborial.getFactorialSeries(11)) echo(Fiborial.getFactorialSeries(40)) // Printing Fibonacci Series echo("") echo(Fiborial.getFibonnaciSeries(5)) echo(Fiborial.getFibonnaciSeries(7)) echo(Fiborial.getFibonnaciSeries(9)) echo(Fiborial.getFibonnaciSeries(11)) echo(Fiborial.getFibonnaciSeries(40)) } }
And the Output is:
Mixing Instance and Static Members in the same Class
Instance classes can contain both, instance and static members such as: fields, getters, constructors/initializers, methods, etc.
// Instance Class class Fiborial { // Instance Field private Int instanceCount // Static Field // Static field 'staticCount' must be const private const static Int staticCount // Instance Read-Only Property Int InstanceCount { get { return &instanceCount } } // Static Fields need to be const. A static const cannot have getter // using Static Read-Only Getter instead // As with Static Methods, you cannot reference your class members // with the "this" reference pointer since static members are not // instantiated. /*static Int StaticCount { get { return &staticCount } }*/ static Int getStaticCount() { return staticCount } // Instance Constructor new make() { this.instanceCount = 0 echo("\nInstance Constructor ${this.instanceCount}") } // Static Constructor // Static constructors are methods executed to initialize the class itself. // They are typically used to initialize static fields. static { staticCount = 0 echo("\nStatic Constructor $staticCount") } // Instance Method Void factorial(Int n) { this.instanceCount += 1 echo("\nFactorial($n)") } // Static Method static Void fibonacci(Int n) { // Error: // Cannot set const static field 'staticCount' outside of static initializer // (static constructor) so we cannot increment staticCount // staticCount += 1 echo("\nFibonacci($n)") } } public class FiborialExtrasApp { public static Void main() { // Calling Static Constructor and Methods // No need to instantiate Fiborial.fibonacci(5) // Calling Instance Constructor and Methods // Instance required Fiborial fib := Fiborial() fib.factorial(5) Fiborial.fibonacci(15) fib.factorial(5) // Calling Instance Constructor and Methods // for a second object Fiborial fib2 := Fiborial() fib2.factorial(5) echo("") // Calling Static Property echo("Static Count = ${Fiborial.getStaticCount}") // Calling Instance Property of object 1 and 2 echo("Instance 1 Count = ${fib.InstanceCount}") echo("Instance 2 Count = ${fib2.InstanceCount}") } }
And the Output is:
Factorial using java.lang.Long/sys::Int, java.lang.Double/sys::Float, java.math.BigInteger
using [java] com.carlosqt.util::Stopwatch using [java] java.math::BigInteger public class FiborialTypesApp { public static Void main() { Stopwatch timer := Stopwatch() Int facIntResult := 0 Float facDblResult := 0f BigInteger facBigResult := BigInteger.ZERO echo("\nFactorial using Int64") // Benchmark Factorial using Int64 for (i := 5; i <= 50; i += 5) { timer.start facIntResult = factorialInt64(i) timer.stop echo(" ($i) = ${timer.getElapsed} : $facIntResult") } echo("\nFactorial using Float/Double") // Benchmark Factorial using Double for (i := 5; i <= 50; i += 5) { timer.start facDblResult = factorialDouble(i) timer.stop echo(" ($i) = ${timer.getElapsed} : $facDblResult") } echo("\nFactorial using BigInteger") // Benchmark Factorial using BigInteger for (i := 5; i <= 50; i += 5) { timer.start(); facBigResult = factorialBigInteger(i); timer.stop(); echo(" ($i) = ${timer.getElapsed} : $facBigResult") } } // Int64 Factorial static Int factorialInt64(Int n) { if (n == 1) return 1 else return n * factorialInt64(n - 1) } // Float Factorial static Float factorialDouble(Int n) { if (n == 1) return 1f else return n * factorialDouble(n - 1) } // BigInteger Factorial static BigInteger factorialBigInteger(Int n) { if (n == 1) return BigInteger.ONE else return BigInteger.valueOf(n).multiply(factorialBigInteger(n - 1)) } }
And the Output is:
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