yawmark.com

Funky Cygwin Path Issues

2011-10-04T08:26:00.000-05:00

In getting familiar with Stuart Sierra's lovely Clojure test library Lazytest, I ran into a problem running it from the windows command console. The test output had special control codes not properly processed by the console:

E:\development\clojure\calibration>java -cp src;test;lib/*;lib/dev/* lazytest.watch src test

======================================================================
At  #<Date Tue Oct 04 07:45:47 CDT 2011>
Reloading calibration.test.core, calibration.core

←[33mNamespaces (no cases run)←[0m

←[33mRan 0 test cases.←[0m
←[32m0 failures.←[0m

Done.

I use mintty for cygwin, which will process those codes correctly, but I then had trouble with the Java classpath:

yawmark$ java -cp "src:test:lib/*:lib/dev/*" lazytest.watch src test
java.lang.NoClassDefFoundError: lazytest/watch
Caused by: java.lang.ClassNotFoundException: lazytest.watch
        at java.net.URLClassLoader$1.run(Unknown Source)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
Could not find the main class: lazytest.watch.  Program will exit.
Exception in thread "main" [~]

After a little online research, I found that I needed to decorate the classpath a bit:

java -cp `cygpath --path --windows "src:test:lib/*:lib/dev/*"` lazytest.watch src test

After that, all is once again right with the world.

2011-06-06T20:28:00.001-05:00

Made it to Times Square. S'pose I can make it anywhere now.

2011-06-06T13:21:00.001-05:00

Off to Manhattan.

2011-02-18T13:05:00.001-06:00

"They didn't care that they'd seen it work in practice because they already knew that it wouldn't work in theory." -- Clay Shirky

SVN Commits To GoogleCode results in 405 error

2011-01-07T08:11:00.002-06:00

I received an unexpected error when committing to GoogleCode that looked like this:

svn: Commit failed (details follow):
svn: Server sent unexpected return value (405 Method Not Allowed) in response to MKCOL request for '....'

ServerFault had the answer. Google code allows anonymous checkout with HTTP, but commits require HTTPS. So, I exported my local workspace changes, blew away the workspace, checked out again with HTTPS, and imported my changes. No commit problems after that, and thank goodness once again for the amount of readily-available information on the Internet.

Bummer

2010-11-29T20:57:00.005-06:00

Inspired by Jeff Atwood's excellent blog about the keyboard cult, I was excited to receive my new Unicomp Customizer 104, delivered just today. To my disappointment, however, it arrived inoperable.

The box itself was in fine condition.

As I removed the keyboard from its packaging, however, I heard an subtle but ominous rattling noise.

I turned the keyboard toward me, and the tilde key fell to the floor. It just fell right off without out any persuasion or cajoling, like it couldn't get away from its compatriots fast enough.

Shortly after that, I noticed that the "CapsLock," "Shift," and "Ctrl" keys on the left side of the keyboard would not depress at all. The underside of the keys overlapped the plastic molding.

The "Enter" key, et al., on the right side had more than adequate spacing.

But the "Esc" key and a few friends were distinctly off-kilter.

I'll give the company call tomorrow and arrange for a working replacement. I hope to report a good customer service experience.

UPDATE (11/30): I got a hold of Chad in the support department. He was very friendly and helpful. Unicomp is sending a replacement today, along with a return label for the original keyboard. So far, so good!

UPDATE (12/02): No longer a bummer! The new keyboard arrived in great shape, and works like a charm. I was hoping for a good customer service experience, and I got it. Thanks, Unicomp!

2010-11-23T12:26:00.001-06:00

Pi is wrong. http://tauday.com/

2010-11-16T07:56:00.001-06:00

Word of the day: "crapulous" http://bit.ly/9zh2Qf

2010-09-10T14:44:00.001-05:00

Be mindful that Tuesday morning problems don't become Friday afternoon problems.

2010-08-19T14:57:00.001-05:00

"Elegance: The modesty not to draw attention to the difficulties one has surmounted." paraphrasing Alain de Botton via @spolsky

2010-08-13T11:25:00.001-05:00

Minimum number of moves to solve any Rubik's cube configuration (aka "God's Number"): 20 http://bbc.in/9rkt7J

2010-07-29T14:05:00.001-05:00

Eclipse tips http://bit.ly/6fq5Zs

2010-07-28T09:23:00.001-05:00

Just read online: "I feel like dancing a marimba." Mambo? Meringue? With a marimba? It's a mystery.

On technical debt

2010-07-28T07:41:00.002-05:00

"Bad code isn't Technical Debt, it's an unhedged call option" http://bit.ly/a3rQcq

2010-07-26T12:53:00.001-05:00

Autism has unique vocal signature, new technology reveals http://bit.ly/b6xg3g

2010-07-24T07:36:00.001-05:00

To market, to market...

2010-07-15T07:56:00.001-05:00

It costs 1.5 cents to make a penny. A nickel costs 6 cents. In 2009, the U.S Mint lost $22 million making these coins. http://bit.ly/9vNeNf

Grails 1.3.1 dependency resolution

2010-05-26T14:22:00.000-05:00

After upgrading Grails to 1.3.1 from 1.2.2, I repeatedly received "UNRESOLVED DEPENDENCIES" errors. After an inordinate amount of troubleshooting, I stumbled upon the sole archived message on the Internet that recommended deleting (or renaming) the %USER_HOME%\.ivy2 directory. Sure enough, this worked like a charm, so I post the resolution here for posterity. It seems there were some transitive dependencies that weren't getting sorted out. It's all good now.

The Light Bulb Is Not Yet On

2010-05-16T21:28:00.000-05:00

I have reset on going through Essentials of Programming Languages, and struggling my way through learning Scheme. I wrote a working answer (at least as tested) for a problem in the second chapter, but I feel like I happened upon it through test-driven development. I suppose in some ways that's a good thing, but I can say that it is not a terribly comfortable feeling to write some code but not really grok what it's doing. Anyway, here is the paraphrased problem, and my solution (test cases included):

Exercise 2.2.9, #3. (car&cdr2 s slst errvalue) generates a procedure composition that, when evaluated, produces the code for a procedure that takes a list with the same structure as slst and returns the value in the same position as the leftmost occurrence of s in slst. If s does not occur in slst, then errvalue is returned.

(define (contains? s los)
  (if (null? los)
      #f
      (if (symbol? (car los))
          (if (eq? s (car los))
              #t
              (contains? s (cdr los)))
          (if (contains? s (car los))
              #t
              (contains? s (cdr los))))))
              
(define (car&cdr2 s slst errvalue)
  (if (contains? s slst)
      (car&cdr2-help s slst 'car)
      errvalue))

(define (car&cdr2-help s slst lst)
  (if (symbol? (car slst))
      (if (eq? s (car slst))
          lst
          (list 'compose lst (car&cdr2-help s (cdr slst) 'cdr)))
      (if (contains? s (car slst))
          (list 'compose 'car (car&cdr2-help s (car slst) 'cdr))
          (list 'compose lst (car&cdr2-help s (cdr slst) 'cdr)))))

Here are the tests (schemeunit):

(define-test-suite 2.2.9
  (test-case "3."
             (check equal?
                    (car&cdr2 'a '() 'fail)
                    'fail)
             (check equal?
                    (car&cdr2 'a '(a) 'fail)
                    'car)
             (check equal?
                    (car&cdr2 'a '(b) 'fail)
                    'fail)
             (check equal?
                    (car&cdr2 'a '(a b) 'fail)
                    'car)
             (check equal?
                    (car&cdr2 'b '(a b) 'fail)
                    '(compose car cdr))
             (check equal? 
                    (car&cdr2 'c '(a b c) 'fail)
                    '(compose car (compose cdr cdr)))
             (check equal? 
                    (car&cdr2 'd '(a (b c) d) 'fail)
                    '(compose car (compose cdr cdr)))
             (check equal?
                    (car&cdr2 'dog '(cat lion (fish dog) pig) 'fail)
                    '(compose car (compose cdr (compose car (compose cdr cdr)))))
             (check equal? 
                    (car&cdr2 'c '((a b) c) 'fail)
                    '(compose car cdr))))

Any Schemers care to give me pointers? I sure could use the help.

Stupid coding tricks.

2010-04-29T08:31:00.000-05:00

In a fit of distraction one day, this was the most ridiculous "solution" for converting a test score to a letter grade I could muster.

public static char S2G(int s) {
    return (char)(1249078710>>s/10*3&7|64);
}

DailyWTF-worthy, I say.

2010-03-20T19:05:00.001-05:00

NCAA Wrestling Championships + ESPN Hi-Def == great television.

2010-03-20T11:04:00.001-05:00

heavyWetSnow.clear();

Estimation and planning

2010-03-09T09:48:00.000-06:00

A 2008 survey of 500 software practitioners found that four of the top five “Most Damaging Classic Mistakes Overall” in software development are directly related to project estimation and planning. Each mistake was rated as having a severe and serious impact to projects in which the mistakes occur. In order of frequency and severity, these four mistakes are:

1. Unrealistic expectations
2. Overly optimistic schedules
4. Wishful thinking
5. Confusing estimates with targets

These are a few of my favorite teams...

2009-12-31T20:25:00.000-06:00

Northwest Bearcats - Division II National Champs
Nebraska Cornhuskers - Holiday Bowl Champs
Iowa State Cyclones - Insight Bowl Champs

It's been a great season.

Veterans Day

2009-11-11T07:50:00.000-06:00

A very thankful Veterans Day, from me and my family. A special gratitude, admiration, and respect for my brother, who is currently serving in Iraq. Here's to wrapping up a successful tour quickly and a safe return home.

Unexpected SimpleDateFormat Behavior

2009-08-27T15:27:00.000-05:00

Failing test case:


import static org.junit.Assert.*;
import java.text.*;
import org.junit.Test;

public class DateFormatTests {

  @Test
  public void testRequiredTwoDigitDay() {
      DateFormat df = new SimpleDateFormat("yyyyMMdd");
      df.setLenient(false);
      try {
          df.parse("2009081");
          fail("Expected two-digit day");
      } catch (ParseException e) {
          e.printStackTrace();
      }
  }
}

Argh.

SimpleDateFormat API Javadocs:

For parsing, the number of pattern letters is ignored unless it's needed to separate two adjacent fields.

Tricksy API javadocs. We hatessss it forever.

Java - Resolving NullPointerException

2009-08-27T06:18:00.001-05:00

In Java, the NullPointerException (NPE) is generally a simple exception to resolve. In very basic terms, it means that one is trying to access a property or call a method on an object that does not exist. Read the error message to find the line where the NPE occurred. Examine that line to determine which reference is a likely candidate to be null. Dig a little deeper to find out why that reference is null and fix the application to either ensure the reference is not null or to handle the reference gracefully if it is null.

Upside down.

2009-08-25T18:55:00.000-05:00

Total U.S. debt held by the public as of August, 2009: $7.3 trillion
Projected deficit for 2010: $1.5 trillion
Total value of all gold ever mined at $941/oz.: $4.8 trillion

My Way: A Tribute To Frank Sinatra

2009-08-03T13:53:00.000-05:00

I was lucky enough to be invited by a friend to perform in "My Way: A Tribute To Frank Sinatra" over this past weekend (7/31 - 8/1/2009). The performance was in Sioux City, IA. It was a great couple of nights; we played to around 1,300 people over the two shows and received standing ovations for both performances. During Friday's performance, we started to get some severe weather around intermission. Randy Peters, the artistic director and his crew moved the entire performance indoors; not a small task. The audience patiently waited for another full setup and sound check, and stuck with us through the second act. What a great group of folks!

The ensemble was as follows:
Sandy Henry (Vocalist)
Don Nelson (Bassist)
Stephen Morrow (Vocalist)
Brad Halbersma (Pianist)
Brenda Ashley (Vocalist)
Kimberly Bata (Percussionist)
Charlie Reese (Vocalist)

I've certainly gained an entirely new appreciation for Sinatra and his music. Among the ensemble pieces, I had several feature solos, including:

"I've Got The World On A String"
"Fly Me To The Moon"
"The Lady Is A Tramp"
"My Lean Baby"
"I've Got You Under My Skin"
"(Love Is) The Tender Trap"
"One For My Baby (And One More For The Road)"
"Summer Wind"
"That's Life"

A full list of the songs from the performance (58!)

And here is an online announcement from the local paper:

Sioux City Journal: Songs of Ol' Blue Eyes presented

I cannot thank the cast and crew enough for letting me be a part of this wonderful show!

What's what about who's who

2009-07-13T17:39:00.000-05:00

Once again, I've been "chosen as a potential candidate" by the Vanity Press. This time it's the "Biltmore Who's Who" folks. They salute me for my executive and professional accomplishments and, given my background, believe my profile would make a "fitting addition" to the Honors Edition of their publication.

That is, if I just fill out the response form to tell them where I work, what industry I'm in, and what my "personal specialty" is.

*snort*

Holy Cow!

2009-06-18T23:04:00.000-05:00

A dinner guest of mine was wearing a bright blue t-shirt with a stylized white portrait of Harry Caray.

My two-year-old daughter informed him, "I like your shirt."

He responded, "Oh, you know who this is?"

She answered, "Yeah. It's God."

Netbeans 6.5 + Grails

2009-04-26T14:09:00.000-05:00

I'm not pleased with the apparent behavior of NetBeans 6.5 when creating a new Grails domain class. I'm unable to create a domain class anywhere other than the default package; the dialog keeps asking for a "valid class name":

This name works fine for creating a Groovy class, just not a Grails domain class. So, why won't the Grails support allow it?

UPDATE (2009-05-08): This seems to be straightened out in NetBeans 6.7 (beta).

XPath Voodoo

2009-04-14T09:53:00.000-05:00

I had a use case for Canoo Web Test to verify the value of a table cell. In an attempt to obtain the value using an XPath query, I used the following expression:

//form[@id='myFormName']/table/tr[2]/td[2]

My test failed, reporting that this expression didn't return any value at all. I verified this was the correct path by looking at the XHTML source. It was only through inspecting the XHTML using the Firebug plugin for Firefox did I see a mystery <tbody> tag. I'm not sure at which point that gets injected, or even why. The injection appears to be a misinterpretation of XTHML 1.0 strict (the specified DOCTYPE). When I added the <tbody> tag to the XPath expression -- which I remind you is not in the XHTML source -- the test passed. Here is the working expression:

//form[@id='myFormName']/table/tbody/tr[2]/td[2]

I haven't figured out what I'm missing, yet.

Justice

2009-04-02T07:29:00.000-05:00

Just today I saw the news that my friend's murderer was found guilty, with sentencing on the way.

I met Dewayne as an EVOC instructor and greatly enjoyed his company during the much-too-short time I got to spend with him. Dewayne's wonderfully affable disposition made him a joy to be around. He never seemed to be without a smile, but he was always ready to take care of business. Hard-working and friendly; Dewayne had these qualities in spades.

SGT Dewayne Graham was a great man, and I'm honored to have known him. I hope this verdict brings some small amount of comfort to his family, and I'm hopeful for swift and severe justice during sentencing.

UPDATE: On May 22, 2009, Dewayne's murderer was sentenced to death.

1,000 excuses

2009-03-31T06:26:00.000-05:00

A good friend of mind said there were thousands of excuses to avoid exercising, but great reward in finding the reason to go ahead and exercise anyway.

Wise words that -- when followed -- always seem to make my day better.

It's here!

2009-03-30T21:45:00.000-05:00

I've started in on "The Definitive Guide to Grails, 2nd Edition," by Graeme Rocher and Jeff Brown, after having just received it via post today. The Groovy/Grails combo never ceases to amaze me. The first couple chapters (as far as I've read, yet) are a simple introduction to the Grails platform, which cover starting up a rudimentary CRUD web application, complete with dynamic scaffolding for a couple related domain classes.

I'm anxiously looking forward to digging into more detail as I'm familiar with the material so far. Slow and steady wins the race, however, and I don't want to risk missing any updated juicy tidbits by skipping ahead.

Estimation error

2009-03-26T19:25:00.000-05:00

"There's no point in being exact about something if you don't even know what you're talking about."
-- John von Neumann, as quoted in "Software Estimation" by Steve McConnell

Software Estimation: Demystifying the Black Art

2009-03-26T12:45:00.000-05:00

At work, I just received "Software Estimation: Demystifying the Black Art," by Steve McConnell. I found his book "Code Complete" to be enlightening and practical, so I'm looking forward to reading what McConnell has to say about the art and science of software estimating. I'll be comparing the text to another favorite of mine; "Agile Estimating and Planning," by Mike Cohn.

The Definitive Guide to Grails, Second Edition

2009-03-23T18:13:00.000-05:00

I'm anxiously awaiting The Definitive Guide to Grails, Second Edition to arrive by mail. I've been playing around with this framework and never cease to be amazed. I understand that other "RAD" web frameworks like Django and Rails probably offer similar features, but Grails' foundation of Groovy is especially attractive to me.

I'll try my best to be patient until TDGG2E shows up.

Hardest. Puzzle. Ever.

2009-03-17T16:14:00.000-05:00

A hundred prisoners are each locked in a room with three pirates, one of whom will walk the plank in the morning. Each prisoner has 10 bottles of wine, one of which has been poisoned; and each pirate has 12 coins, one of which is counterfeit and weighs either more or less than a genuine coin. In the room is a single switch, which the prisoner may either leave as it is, or flip. Before being led into the rooms, the prisoners are all made to wear either a red hat or a blue hat; they can see all the other prisoners' hats, but not their own. Meanwhile, a six-digit prime number of monkeys multiply until their digits reverse, then all have to get across a river using a canoe that can hold at most two monkeys at a time. But half the monkeys always lie and the other half always tell the truth. Given that the Nth prisoner knows that one of the monkeys doesn't know that a pirate doesn't know the product of two numbers between 1 and 100 without knowing that the N+1th prisoner has flipped the switch in his room or not after having determined which bottle of wine was poisoned and what colour his hat is, what is the solution to this puzzle?

Heh.

Public Key

2009-03-16T17:19:00.001-05:00

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Version: GnuPG v1.4.9 (Cygwin)

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JtHSbp9JyOH8/CWAGJf36CsMI9JEm9eTnaZcNvXqfqkFXah3iFn1IBOKkwCgm5uJ
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Getting What You Want

2009-03-12T08:38:00.000-05:00

"The indispensable first step to getting what you want is this: Decide what you want."
-- Ben Stein

This is soaring?

2009-03-10T15:12:00.000-05:00

Yahoo!® Finance reports today that "Stocks Soar on Bank Rally." Not to rain on anyone's parade, but a 380-point bounce in the Dow after losing more than 50% of its market value since last October (a high of 14,093 to 6,547 yesterday) is not what I'd call "soaring," given the context.

...And Pretty Soon You're Talking About Real Money

2009-03-09T11:25:00.000-05:00

Global Financial Assets Lost $50 Trillion Last Year, ADB Says

Theory vs. Practice

2009-03-08T14:41:00.000-05:00

"The difference between theory and practice is smaller in theory than in practice."
-- Unattributed

Bigger than a breadbox

2009-03-05T15:19:00.001-06:00

What a trillion dollars looks like.

"Holidays The Healthy Way" Weight Loss Challenge

2009-02-22T10:18:00.000-06:00

Recently at work, we had a "weight loss challenge" that started in early December and ran through February 13, 2009. With the expert help of my live-in chef and nutritionist (aka, Terri), I won the competition by a healthy margin. I started at ~208 pounds and finished the competition around 176, losing around 32 pounds (a little over 15% of my total body weight) in ten weeks. The big secret to my success was watching what I eat and exercising regularly. I know that's not a particularly revolutionary idea, but it's one many of us - that is, me - seem to struggle with. For the most part, however, once I paid close attention to what I ate and how much exercise I did week-to-week, the process managed itself.

The goal now is to keep working on converting fat to muscle and not fall back into bad habits. :)

Facebook is the new crack.

2009-02-22T09:38:00.000-06:00

I'm just sayin'.

Or maybe it's the old crack and I'm just that far behind the times.

Update: "Days Difference" with Joda

2008-06-21T09:02:00.000-05:00

The more I play with the Joda Time API, the more I like it. Revisiting the "calculating difference in days" problem, here's the Joda/Groovy equivalent:

import org.joda.time.LocalDate
import static org.joda.time.Days.*

date1 = new LocalDate(2008, 3, 10)
date2 = new LocalDate(2008, 3, 12)
assert 2 == daysBetween(date1, date2).days

What's not to like? :o)

DGG Confusion #1 (among many to come, I'm sure)

2008-05-16T22:27:00.000-05:00

I'm working my way through The Definitive Guide to Grails. Chapter 6 covers testing, and I'm a bit stuck on the GroovyMock example in listing 6-9. I'm using Grails 1.0.2, and as entered*, the test fails with "No call to 'getParams' expected at this point. Still 1 call(s) to 'redirect' expected." I tried demanding a call to getParams, but that leads down a path of yet more confusing errors.

So, I'll keep beating my head against it for a while, and hopefully post back with some results.

*

void testUpdateNotFound() {
 def bc
 def mock = new MockFor(BookmarkController)
 mock.demand.redirect { Map params ->
     assert params.action == bc.edit
 }
 mock.use {
     bc = new BookmarkController()
     bc.params.id = 5
     bc.update.call()
 }
}

[UPDATE] Nothing that a little Googling won't help, and I'm happy to know I'm not just insane (well, at least not with this particular problem). I'm using version 1.5.1, and according to a bug report, Groovy's MockFor is a bit squiffy in versions 1.5.1 and 1.5.4. Unfortunately, the bug's still open, so I'll have to pass over that part of the book for now. I can do that in good conscience. :o)

[UPDATE #2] This works with Groovy 1.5.6 (with "method pointers"):

import groovy.mock.interceptor.*

class BookmarkController {
    def update = { redirect("value from original") }
    def redirect = { println "Original class: $it" }
}

class BookmarkTests extends GroovyTestCase {
    void testUpdate() {
        def bc
        def mock = new MockFor(BookmarkController)
        mock.demand.redirect { println "Mock class: $it" }
        mock.use {
            bc = new BookmarkController() 
            bc.&update.call()
        }
    }
}

new BookmarkController().&update.call()
new BookmarkTests().testUpdate()

...but I'm not sure that does much for DGG Listing 6-9. Hmph.

Confusion

2007-12-26T10:24:00.000-06:00

On two occasions I have been asked, – "Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?" In one case a member of the Upper, and in the other a member of the Lower, House put this question. I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a question.

-- Charles Babbage, English mathematician, philosopher, and mechanical engineer

Calculate Difference in Days

2007-12-22T19:07:00.000-06:00

Java has no built-in "give me the difference in days" API methods. One commonly-suggested solution is to get the difference in milliseconds between two dates and, using the number of milliseconds in a day, determine the number of days. Unfortunately, daylight savings time creates some problems with this method, as the following Groovy script demonstrates:

#! /usr/bin/groovy

df = new java.text.SimpleDateFormat('yyyy-MM-dd')

// These dates cross DST...
startDate = df.parse('2007-03-10')
endDate = df.parse('2007-03-12')

expectedDifferenceInDays = 2

// Here's the problem with millis:
millisInADay = 1000 * 60 * 60 * 24
differenceInMillis = endDate.time - startDate.time
actualDifferenceInDays = differenceInMillis / millisInADay

assert expectedDifferenceInDays != actualDifferenceInDays
assert actualDifferenceInDays < expectedDifferenceInDays

Here's a more straightforward solution using Java's Calendar API:

#! /usr/bin/groovy

df = new java.text.SimpleDateFormat('yyyy-MM-dd')

// These dates cross DST...
startDate = df.parse('2007-03-10')
endDate = df.parse('2007-03-12')

expectedDifferenceInDays = 2

calendar = Calendar.instance
calendar.time = startDate
actualDifferenceInDays = 0
while (calendar.time.before(endDate)) {
    actualDifferenceInDays++
    calendar.add(Calendar.DATE, 1)
}
assert expectedDifferenceInDays == actualDifferenceInDays

Note that what constitutes "a day" is subject to interpretation... :o)

Write simple code

2007-10-03T07:12:00.000-05:00

Debugging is twice as hard as writing the code in the first place. Therefore, if you write the code as cleverly as possible, you are, by definition, not smart enough to debug it.
-- attributed to Brian Kernighan

Integer Palindromes

2007-09-14T23:14:00.000-05:00

File this one under "Silly, Simple Code Snippet Of The Day"™...

Several times on various programming forums, I've seen question about how to find out if an integer value is a palindrome or not (the number is the same "forwards" and "backwards"; e.g., 71317 would be a palindrome, while 71316 would not). Most of the suggested solutions revolve around converting the integer value to a string and reversing the characters. This makes sense, given that "71317" is just a character representation of a number, and many language APIs have ready-made facilities for reversing strings of characters (or at least arrays). That said, finding out if a number is a palindrome using basic math is dead simple, too. Here's a base-10 example in C#:

    using System.Diagnostics;

    class ScratchUtils
    {
        public static int Reverse(int i)
        {
            int result = 0;
            while (i != 0)
            {
                result = (result * 10) + (i % 10);
                i /= 10;
            }
            return result;
        }

        public static bool IsPalindrome(int i)
        {
            return i == Reverse(i);
        }

        public static void Main()
        {
            Debug.Assert(  0 == Reverse(0));
            Debug.Assert(  1 == Reverse(1));
            Debug.Assert( 21 == Reverse(12));
            Debug.Assert(-21 == Reverse(-12));

            Debug.Assert(IsPalindrome(1));
            Debug.Assert(IsPalindrome(11));
            Debug.Assert(!IsPalindrome(12));
            Debug.Assert(IsPalindrome(121));
        }
    }

Java - Cannot Resolve Symbol

2007-09-11T09:45:00.000-05:00

You get a "cannot resolve symbol" message because the compiler doesn't recognize something you've typed. It's as if you instructed your friend to "fernt PL^%", to which s/he would likely reply, "Huh?". The compiler errors will tell exactly which symbols it does not recognize; correct these errors by properly defining variables, importing the correct classes, implementing the appropriate methods, etc.

.NET - Connecting to SQL Server Express from VWDE

2007-09-02T11:52:00.000-05:00

I was trying a tutorial for Visual Web Developer Express, and kept running into problems connecting to SQL Server Express. When I tried to configure the security settings by clicking on the security tab in the ASP.NET Web Site Administration Tool, I received the following error:

There is a problem with your selected data store. This can be caused by an invalid server name or credentials, or by insufficient permission. It can also be caused by the role manager feature not being enabled. Click the button below to be redirected to a page where you can choose a new data store.

After researching a bit, I used the SQL Server Configuration Manager to use "Local System" as the built-in account (found under the [Log On] tab for the running SQL Server Express instance). Then, I had to add a Web.config to my project with the following connection strings:

<connectionStrings>
  <remove name="LocalSqlServer"/>
  <add name="LocalSqlServer"
   connectionString="Data Source=localhost;
         Initial Catalog=aspnetdb;
         Integrated Security=True"
     providerName="System.Data.SqlClient"/>
</connectionStrings>

After that, the connection succeeded, and I was able to continue with the tutorial.

Newsbite Of The Day

2007-08-15T10:16:00.000-05:00

From a story about rising food prices:

Half the nation’s families earn below the median family income of about $56,000.

Well, yeah. That's pretty much what "median" means.

In other shocking news, half the nation’s families earn above the median family income of about $56,000.

Groovy and the Lambda Calculus

2007-07-06T23:51:00.000-05:00

I've been playing around with the Groovy language, and have recently been involved in a discussion regarding the addition of closures to Java. Tangents lead to tangents, and all of a sudden, I find myself reading about Perl and the Lambda Calculus. Oy.

I had just started trying to get my head around the idea of the lambda calculus when the author brought up the subject of "currying", and discussed the "Lambda Calculus Way"™ of writing an addition function built on the concept that functions can only take a single argument. The author showed how to express such a thing in Perl:

    sub add {
        my $x = shift;
        my $f = sub {
            my $y = shift;
            return $x + $y;
        }
        return $f;   
    }

Groovy supports writing code like this too, so I thought I'd see what I could come up with in Groovy syntax. Here's the beast:

    def add (x) {
        return {
            y -> return x + y
        }
    }

And the test...

    assert 7 == add(3)(4) // whew.

If there's a Groovy expert out there reading this blog, let me know if there's a better way. All right, back to the essay...

Independence Day

2007-07-04T09:38:00.000-05:00

Have a happy and safe Independence Day!

Non-Static Members and Static Contexts

2007-07-04T09:09:00.000-05:00

A question commonly asked on Java forums concerns an error message similar to the following:

non-static variable cannot be referenced from a static context

In Java, static means "something pertaining to an object class". Often, the term class is substituted for static, as in "class method" or "class variable." Non-static, on the other hand, means "something pertaining to an actual instance of an object. Similarly, the term instance is often substituted for non-static, as in "instance method" or "instance variable."

The error comes about because static members (methods, variables, classes, etc.) don't require an instance of the object to be accessed; they belong to the class. But a non-static member belongs to an instance -- an individual object. There's no way in a static context to know which instance's variable to use or method to call. Indeed, there may not be any instances at all! Thus, the compiler happily tells you that you can't access an instance member (non-static) from a class context (static).

Java Strings and Hash Codes

2007-06-25T10:42:00.000-05:00

The question often arises as to how Java can use String values in switch/case statements; e.g.:

switch(s) {
    case "Foo": doSomething();     break;
    case "Bar": doSomethingElse(); break;
}

The short answer is that one can't. In Java (versions before 5), the expression evaluated in the switch statement must be a char, byte, short, or int. With auto-unboxing and the new enum capabilities of Java 5 and later versions, switch expression may also include Character, Byte, Short, Integer, or enum types. Furthermore, every case expression must be assignable to the same type as what is declared in the switch statement. This means that if your switch statement is an int type, your case statements can be int types, byte types, short types, etc. If, on the other hand, your switch statement is a byte type, the compiler will bark if you try to use an int type in a case expression. In short, however, switch statements with String types (and any type not mentioned above) are simply not available in Java.

Back to the problem of using String values... Every so often, someone will suggest using the string's hash code (an int value) as the value to use as a switch. There are a couple problems with this idea. First, the case expressions must be constant, meaning that the compiler isn't going to accept the result of hashCode() as a valid case. Second, and perhaps a more fundamental issue, string hash codes aren't guaranteed to be unique. Far from it, in fact. The only thing string hash codes guarantee is that strings with different hash codes are guaranteed to be not equal.

So, what is an appropriate solution? It all depends on the design, of course. Most likely, using enums would be a fair approach. In his seminal book Refactoring, Martin Fowler recommends looking at polymorphism for a more object-oriented design. And if one must have switchy strings in a Java-ish environment, there is always Groovy...

~

Final Variables and Anonymous Inner Classes

2007-06-21T08:15:00.000-05:00

Anonymous inner classes require final variables because of the way they are implemented in Java. An anonymous inner class (AIC) uses local variables by creating a private instance field which holds a copy of the value of the local variable. The inner class isn't actually using the local variable, but a copy. It should be fairly obvious at this point that a "Bad Thing"™ can happen if either the original value or the copied value changes; there will be some unexpected data synchronization problems. In order to prevent this kind of problem, Java requires you to mark local variables that will be used by the AIC as final (i.e., unchangeable). This guarantees that the inner class' copies of local variables will always match the actual values.

~

The Usual Suspects

2007-06-21T08:12:00.001-05:00

He burns down the threads they post in and the forums they lurk in, he deletes accounts of recurring trolls. And like *that*...

...he was gone.

Underground.

No one has ever seen him again. He becomes a myth, a spook story that regulars tell their kids at night. If you write "i = i++", Keyser Sunze will get you.

And nobody really ever believes...

Links

2006-11-10T13:10:00.000-06:00

The Java Language Specification