Grails proxy settings

I always forget these.

1. When setting the details from the (Windows) command line, use quotes everywhere:
> grails add-proxy someProxyName "--host=the.host.name" "--port=8080" "--username=myUserName" "--password=myPassword"

2. Don't forget to set-proxy:
> grails set-proxy someProxyName

3. The ProxySettings.groovy file is stored in the top level of .grails - not in the 1.3.5 subdirectory etc.

Online book shopping

For some professional development, and to see what Uncle Bob is on about, I decided to buy Structure and Interpretation of Computer Programs (SICP).

I was impressed that QBD Online had a price (including delivery) of $53.95. This was comparable to Amazon ($53.18), and Book Depository ($57.54). (It's available for free online, but I think I'd rather pay for a hard copy.) I ordered through QBD. Eleven days later (admittedly some were public holidays), they informed me that they were "temporarily out of stock", and the publisher couldn't advise when more stock would be available. I wasn't happy, and asked them to cancel the order. I was pleasantly surprised to see that they responded very quickly (cancel requested 9pm, response at 6am). It means that I'm more likely to go back to them in future.

It was simple to order the book at Amazon. They said that the book was in stock. Twelve hours later I have an email saying that the book has been shipped. Nice contrast.

Setting up Scholastic "I Spy Fantasy" for non-administrative users

My children have non-administrator accounts on their computers, one of which uses Windows XP. Maybe that doesn't encourage them to learn, but that's how it is at the moment. They wanted to install (again) I Spy Fantasy, an old game, but it required administrative access. That was ok. But then we found that administrative access was required not just to install, but also to play the game. That's not ok.

A short web search didn't yield any answers, so I delved. The error message reported that it couldn't save game details to the disk. Probably because it stores the saved games in C:\Program Files\Scholastic...

I tried to move the saved games folder, and make a shortcut, but that seemed fruitless. So I moved the whole installation folder from Program Files to daughter's Documents and Settings folder. But when running the application, it still complained about the same problem. I wondered if the registry was pointing to the old location. Sure enough - Local Computer/Software/Scholastic inc/I Spy Fantasy/install-dir pointed to Program Files... . So I changed that, switched users back to the non-administrative account, and tried again. This time, the error message was new: the program was trying to modify the registry! Well, it looks like in regedit, you can set permissions for different entries. So I gave the non-privileged user full control for just the I Spy Fantasy folder. That's better.

Oops. One last problem. Don't forget to adjust where the start menu shortcut points to!

That seems to have solved the problem. I wonder if anyone else cares about such things. Maybe you'll leave me  a comment if this helps.

Prime factors coding kata using transformations.

Inspired by Uncle Bob's Transformation Priority Premise, Glennn and I tried a Groovy kata.

  @Test
  void shouldReturnPrimeFactors(){
    assertThat getPrimeFactors(1), equalTo([])
    assertThat getPrimeFactors(2), equalTo([2])
    assertThat getPrimeFactors(3), equalTo([3])
    assertThat getPrimeFactors(4), equalTo([2,2])
    assertThat getPrimeFactors(5), equalTo([5])
    assertThat getPrimeFactors(6), equalTo([2,3])
    assertThat getPrimeFactors(7), equalTo([7])
    assertThat getPrimeFactors(8), equalTo([2,2,2])
    assertThat getPrimeFactors(9), equalTo([3,3])
    assertThat getPrimeFactors(10), equalTo([2,5])
    assertThat getPrimeFactors(11), equalTo([11])
    assertThat getPrimeFactors(12), equalTo([2,2,3])
    assertThat getPrimeFactors(13), equalTo([13])
    assertThat getPrimeFactors(14), equalTo([2,7])
    assertThat getPrimeFactors(15), equalTo([3,5])
    assertThat getPrimeFactors(16), equalTo([2,2,2,2])
    assertThat getPrimeFactors(17), equalTo([17])
    assertThat getPrimeFactors(18), equalTo([2,3,3])

    assertThat getPrimeFactors(25), equalTo([5,5])

    assertThat getPrimeFactors(64), equalTo([2,2,2,2,2,2])

    assertThat getPrimeFactors(74), equalTo([2,37])
}


We didn't record everything as we went. It would have been good to look back at our mistakes. But here's the steps I took when re-doing it later.

Step 1. "{} -> nil" transformation. Suceeds for 1, fails at 2.
  static def getPrimeFactors(int number) {
    return []
  }


Step 2. "unconditional -> if" transformation. Succeeds up to 3, fails at 4.
  static def getPrimeFactors(int number) {
    if (number == 1) return []
    return [number]
  }


Step 3. "unconditional -> if" transformation and "statement-> recursion" transformation. Fails at 9.
  static def getPrimeFactors(int number) {
    if (number == 1) return []
    if (number%2 == 0) {
      return [2]+getPrimeFactors(number.intdiv(2))
    }
    return [number]
  }


Step 4. "unconditional -> if" transformation. Fails at 25.
  static def getPrimeFactors(int number) {
    if (number == 1) return []
    if (number%2 == 0) {
      return [2]+getPrimeFactors(number.intdiv(2))
    }
    if (number%3 == 0) {
      return [3]+getPrimeFactors(number.intdiv(3))
    }
    return [number]
  }


Step 5. Refactor to remove duplication. No change to behaviour.
  static def getPrimeFactors(int number) {
    if (number == 1) return []
    for (int divisor=2; divisor<=3; divisor++) {
      if (number % divisor == 0) {
        return [divisor] + getPrimeFactors(number.intdiv(divisor))
      }
    }
    return [number]
  }


Step 6. "constant -> scalar" transformation. Success for all cases.
  static def getPrimeFactors(int number) {
    if (number == 1) return []
    for (int divisor=2; divisor*divisor<=number; divisor++) {
      if (number % divisor == 0) {
        return [divisor] + getPrimeFactors(number.intdiv(divisor))
      }
    }
    return [number]
  }

One slightly undesirable characteristic is that this method attempts to use composite divisors, although these can never succeed. Some may consider it better to construct a list of primes as potential divisors. I'll look into this another time, but I suspect that the additional work to construct the list of primes will add complexity, and not improve performance too much (unless the primes are calculated just once, and there are many calls to getPrimeFactors).