Java and Scala, a demonstration in code.

[wtd]

A little demonstration of Scala, and what it can do, with regards to recursion.

Also a bit of comparison between Test.java and ScalaTest.scala.

code:

C:\Documents and Settings\Chris\My Documents\scala>type mymath\Factorial.scala package mymath import java.math.BigInteger import BigInteger.ONE object Factorial {     def apply(n: Int): BigInteger = {         def aux(n: BigInteger, acc: BigInteger): BigInteger = {             val comparison = n compareTo ONE             if (comparison == -1 || comparison == 0) acc             else aux(n subtract ONE, acc multiply n)         }         aux(new BigInteger(n toString), ONE)     } } C:\Documents and Settings\Chris\My Documents\scala>type Test.java import mymath.Factorial; public class Test {     public static void main(String[] args) {         System.out.println(Factorial.apply(400));     } } C:\Documents and Settings\Chris\My Documents\scala>scalac -classpath . mymath\Factorial.scala C:\Documents and Settings\Chris\My Documents\scala>javac -classpath . Test.java C:\Documents and Settings\Chris\My Documents\scala>scala -classpath . Test 640345228466238952623479703195030058507025830260029594586844459428023971691868314362784786474632646762943505750358568108 482981628835174352289619886468029979373416541508381624264619423523070462443250151144486708906627739149181173319559964407 095496713452904770203224349112107975932807951015453726672516278778900093497637657103263503315339653498683868313393520243 737881577867915063118587026182701698197400629830253085912983461622723045583395207596115053022360868104332972551948526744 322324386699484224042325998055516106359423769613992319171340638589965379701478272066063202173794720103213566246138090779 423045973606995675958360961587151299138222865785795493616176544804532220078258184008484364155912294542753848035583745180 226759000613995601455952061272111929181050324910080000000000000000000000000000000000000000000000000000000000000000000000 00000000000000000000000000000 C:\Documents and Settings\Chris\My Documents\scala>type ScalaTest.scala import mymath.Factorial object ScalaTest extends Application {     Console println Factorial(400) } C:\Documents and Settings\Chris\My Documents\scala>scalac -classpath . ScalaTest.scala C:\Documents and Settings\Chris\My Documents\scala>scala -classpath . ScalaTest 640345228466238952623479703195030058507025830260029594586844459428023971691868314362784786474632646762943505750358568108 482981628835174352289619886468029979373416541508381624264619423523070462443250151144486708906627739149181173319559964407 095496713452904770203224349112107975932807951015453726672516278778900093497637657103263503315339653498683868313393520243 737881577867915063118587026182701698197400629830253085912983461622723045583395207596115053022360868104332972551948526744 322324386699484224042325998055516106359423769613992319171340638589965379701478272066063202173794720103213566246138090779 423045973606995675958360961587151299138222865785795493616176544804532220078258184008484364155912294542753848035583745180 226759000613995601455952061272111929181050324910080000000000000000000000000000000000000000000000000000000000000000000000 00000000000000000000000000000 C:\Documents and Settings\Chris\My Documents\scala>

[Clayton]

is Scala an extension of sorts to Java? Either way, i fail to see what you are trying to show us, please enlighten me about what you are trying to show.

[md]

Scala is another language that runs on the java virtual machine. It's considerably more powerful then Java.

[wtd]

In Java, there is no tail-call optimization, so trying to find the factorial of large numbers would result in a stack overflow.

Scala can implement factorial recursively, and it has efficient runtime characteristics.

[md]

tail-call optimizations are cool, very very nifty if you do any assembly level stuff as well

[zylum]

my version of the recursive factorial function can calculate 5745! before a stack overflow occures.. I dont thing that is too bad 19105 digits

JAVA:

import java.math.*; class Factorial {         public static void main (String [] args)         {         System.out.println(factorial(new BigInteger(args[0]), BigInteger.ONE).length());         }                 static String factorial (BigInteger n, BigInteger ret)         {                 if (n.compareTo(BigInteger.ZERO) == 0 || n.compareTo(BigInteger.ONE) == 0) return ret.toString();                 else return factorial(n.subtract(BigInteger.ONE), ret.multiply(n));         }   }

[rizzix]

yea scala == fun.. i particularly like the pattern matching..

most of my newer projects are in scala.

Scala (java) frontend and a haskell backend.. Its a prefect combo!