GIGO: words unreadable aloud
Mishrogo Weedapeval
 

 

  Friday 14 May 2004
Chapter 4, Exercises 3-5

Note that all three of tonight's exercises use the class c4x2c, which we built yesterday. In order to use it, we must now (for the first time) use a -classpath . argument in the (scalac) compile step.

http://theclapp.blog-city.com/read/11120.htm
http://theclapp.blog-city.com/read/11272.htm
http://theclapp.blog-city.com/read/11276.htm

Chapter 4, Exercise 3

object c4x3 {
    def main ( args: Array[String] ) = {
        val ar = new Array[ c4x2c ]( 10 );
        Console.println( "Note, no talky constructors are called." );
    }
}

Chapter 4, Exercise 4

object c4x4 {
    def main ( args: Array[String] ) = {
        val ar = new Array[ c4x2c ]( 10 );
        Console.println( "Note, no talky constructors are called yet." );
        for (val i <- Iterator.range( 0, ar.length ) ) {
            val s: String = "msg " + i;
            ar(i) = new c4x2c(s);
        }
    }
}

Chapter 4, Exercise 5

object c4x5 {
    def main ( args: Array[String] ) = {
        val ar = new Array[ String ]( 10 );
        for (val i <- Iterator.range( 0, ar.length ) )
            ar(i) = new String( "i = " + i );

        for (val i <- Iterator.range( 0, ar.length ) )
            Console.println( "ar(" + i + ") = " + ar(i) );
    }
}

10:27:23 PM   comment/     
Chapter 4, Exercises 1-2, Thinking in Scala

Chapter 4, Exercise 1

I wonder how one declares ... or even whether one can declare ... and implement a no-argument constructor to do some action (like, say, printing a log message) upon the creating of a c4x1c, without having to do it in an overloaded constructor. For this exercise, I added some extra println's. 
class c4x1c {
    def this ( i:Int ) = {
        this();
        Console.println( "    ... creating a c4x1c, with argument " + i );
    }
}
object c4x1 {
    def main ( args: Array[String] ) = {
        Console.println( "Declaring a c4x1c 'o' ..." );
        val o = new c4x1c;
        Console.println( "Declaring a c4x1c 'p' (1) ..." );
        val p = new c4x1c(1);
        Console.println( "Declaring a c4x1c 'q' (2) ..." );
        val q = new c4x1c(2);
        Console.println( "All done." );
    }
}

Chapter 4, Exercise 2

Overloaded constructors are a little weird in Scala. The name is always "this", and the the parser won't accept the definition unless the first thing it does is a call to another constructor. The no-argument constructor is, I gather, the basic one that the compiler generates. I guess that answers the wonder in the first half of this posting. 
class c4x2c {
    def this ( i:Int ) = {
        this();
        Console.println( "    ... creating a c4x2c, with int argument " + i );
    }
    def this ( s:String ) = {
        this();
        Console.println( "    ... creating a c4x2c, with String argument '"
                       + s + "'." );
    }
}
object c4x2 {
    def main ( args: Array[String] ) = {
        Console.println( "Declaring a c4x2c 'o' ..." );
        val o = new c4x2c;
        Console.println( "Declaring a c4x2c 'p' (1) ..." );
        val p = new c4x2c(1);
        Console.println( "Declaring a c4x2c 'q' (2) ..." );
        val q = new c4x2c(2);
        Console.println( "Declaring a c4x2c 'r' (Last One) ..." );
        val r = new c4x2c( "Last One" );
        Console.println( "All done." );
    }
}

PS, I talked a bit with Bruce Eckel tonight at the Python BayPIGgies meeting, and told him about this Scala effort here on GIGO, and about THECLAPP series in Java and Lisp, as well as Bill Clementson's catalog of the CLAPP one. I put a brief review of the Python meeting on my zia weblog.
1:24:31 AM   comment/     


Click here to visit the Radio UserLand website. Click to see the XML version of this web page. © Copyright 2007 Doug Landauer .
Last update: 07/2/6; 12:39:28 .
Click here to send an email to the editor of this weblog.

About Me & GIGO
GIGO TOC
Remember "Portals"?
Bay Area WebRing:
< # BayAreaBloggers ? >
jenett.radio.randomizer - click to visit a random Radio weblog - for information, contact randomizer@coolstop.comRandom radio Weblog

blogchalk: Doug/yob.1952. Lives in California/Santa Cruz Mountains/Blue Tarp Town: 37n05/122w05. Speaks English. Sometimes. Spends 40% of daytime online most days. Uses a DSL connection
stories
(my static site)
(my 2D portal)
(F Train)
(defective yeti)
(pgmr reddit)
(Lambda)

May 2004
Sun Mon Tue Wed Thu Fri Sat
            1
2 3 4 5 6 7 8
9 10 11 12 13 14 15
16 17 18 19 20 21 22
23 24 25 26 27 28 29
30 31          
Apr   Jun

Previous/Next