A friend of mine defended Fortran against half-literate coders on an example of Prim’s allgorithm.

Good pretext for another language comparison. Let’s see Groovy vs Java vs good old Fortran.

Great Fortran implementation

Great Java implementation by Bruno R. Preiss, P.Eng. and scientist.

Some beginner’s C+ implementation (or is it just a link farm? Whatever).

And here’s the algorithm in Groovy, copied as precisely as possible from pseudocode in Russian Wikipedia article.

class Edge {
    Integer v1
    Integer v2
    Integer weight

    Edge(Integer v1, Integer v2, Integer w) {
        this.v1 = v1
        this.v2 = v2
        this.weight = w
    }

    boolean contains(Integer v) { v1 == v || v2 == v }
    Integer otherThan(Integer v) { v1 == v ? v2 : v1 }
}

class Graph {
    List<Integer> V
    Collection<Edge> E

    // Dumbest implementation
    List<Integer> getIncident(Integer v) { E.findAll{ it.contains(v) }.collect{ it.otherThan(v) } }
    Edge findEdge(Integer v1, Integer v2) { E.find{ it.contains(v1) && it.contains(v2) } }
    Number weight(Integer v1, Integer v2) { findEdge(v1, v2)?.weight ?: Double.POSITIVE_INFINITY }
}

Collection<Edge> prim(Graph G) {
    Set<Edge> T = []
    Map<Integer, Number> d = [:] + G.V.collect { new MapEntry(it, Double.POSITIVE_INFINITY) }
    Map<Integer, Integer> p = [:] + G.V.collect { new MapEntry(it, null) }
    d[G.V[0]] = 0

    List<Integer> Q = G.V.collect{it}
    Q.metaClass.extractMin = { ->
        // Dumbest implementation
        int minimum = Q.min { d[it] }
        int indexOfMinimum = Q.indexOf(minimum) // here Groovy fails to make a shortcut.
        return Q.remove(indexOfMinimum)
    }

    Integer v = Q.extractMin()
    while (!Q.isEmpty()) {
        G.getIncident(v).each { Integer u ->
            if(Q.contains(u) && G.weight(u, v) < d[u]) {
                d[u] = G.weight(u, v)
                p[u] = v
            }
        }
        v = Q.extractMin()
        T << G.findEdge(p[v], v)
    }

    return T
}

void testPrim() {
    Set<Edge> expected = [
        new Edge(1, 2, 1),
        new Edge(2, 3, 1),
        new Edge(3, 4, 1),
        new Edge(4, 5, 1),
    ]

    Set<Edge> edges = [
        new Edge(1, 3, 2),
        new Edge(1, 4, 3),
        new Edge(1, 5, 2),
        new Edge(2, 4, 7),
        new Edge(3, 5, 2),
    ]

    Graph G = new Graph(V: 1..5, E: expected + edges)

    Set<Edge> T = prim(G)
    assert expected.equals(T)
    println "it worked!"
}

testPrim()

Not too bad, er? I see only a couple of Groovy overhead points: constructing a Map from collect{}, and absence of findIndexOfMin().
Of course, we could avoid long type declarations, but I like strict typing.
Make your conclusions.

I’m thinking of precise Redmine burdown chart, which is not so simple.

• It has to build burdown chart for a given sprint (Version in Redmine).
• It has to account issues added to Version and removed from during the sprint.
• It, after all, has to account for what is considered “closed” status, which might be one of non-stock, custom statuses.

There are couple of Redmine addons, but for now I’m precautious about installing them. They are:

• ScrumAlliance Burndown is outdated and unsupported for now;
• RedmineBacklogs looks very promising and tasty.

For now, I do it by hand. I put together a SQL query to get me the data:

select
  i.id, i.subject, i.estimated_hours,
  j.created_on, jd.value, s.name new_status,
  old_versions.name old_version,
  new_versions.name new_version

from
  issues i
  inner join journals j on j.journalized_id = i.id and j.journalized_type = 'Issue'
  inner join journal_details jd on jd.journal_id = j.id
  inner join versions on i.fixed_version_id = versions.id
  left outer join issue_statuses s on s.id = jd.value
  left outer join versions old_versions
    on jd.prop_key = 'fixed_version_id'
      and jd.old_value = old_versions.id
  left outer join versions new_versions
    on jd.prop_key = 'fixed_version_id'
      and jd.value = new_versions.id

where
  (versions.name = '1.0.8' or old_versions.name = '1.0.8' or new_versions.name = '1.0.8')
  and property = 'attr'
  and jd.prop_key in ('status_id', 'fixed_version_id')

order by i.id, created_on

Just published a library I created on one of past jobs out of Updater Application Block and WiX’s ClichThrough component.
Please meet: DotUpdater
It can auto-update an application, just create a RSS feed of updates and Windows Installer (MSI) binaries.

Imagine a task (actually, quite common), if you have:

• a nodes (articles, ads, whatever) taxonomy in Drupal,
• a taxonomy-based url path rewrites, like /monkeys/primates/homosapiens
• and want to show a block/page View with articles only from current path term (and, maybe, its subterms).

It might be a hard time finding out the current term. One could try having two nested views, passing a current term as a parameter to nested view, like Dustin Currie did.

Though, Views has several pre-defined solutions. Just go to /admin/build/views/ and enable this one: “Default Node view: taxonomy_term”, (clone it to play safe), voila!

You got a View for the current term.

In case you, like me, need to compare version of Office documents (under Windows), just know that TortoiseSVN got a pretty set of scripts for that.
It works out of box!
YES!
You can compare Office documents just like plaintext files!.
Just tried it and it worked. If you were afraid of trying, like me – don’t be.

We’re trying Grails, Rails-like web application framework for Java.
It’s fine, just that Groovy debugger support is, er, imperfect, even in the best Gruoovy IDE – IDEA.

And, if you want to unit test, you won’t have fancy domain class methods addTo* – like Customer.addToOrders().
They’re generated by Grails on startup.
In order to have addTo*(), inherit from GrailsUnitTestCase and call mockDomain(Customer) in setUp().

Oh, if you get "NullPointerException: Cannot invoke method containsKey() on null object", add super.setUp() to yout testcase’s setUp().

Having proper save() is more tricky. Implementation from mockDomain() works to some extent: it won’t save connected objects.
So, in order to get save() working, you have to do something like this:

    def savedCustomers = []

    void setUp() {
        super.setUp()
        Customer.metaClass.save = { saveCustomer(delegate) }
        mockDomain(Customer, savedCustomers)
    }

    private def saveCustomer(c) {
        savedCustomers.add(c)
        if (c.orders != null) {
            c.orders.each { x -> x.save() }
        }
    }

Just dealt with another Visual Studio 2008 “feature”.

You can specify all the necessary “Project Dependencies” in Visual Studio, but will get “CSC : error CS0006: Metadata file FooBar.dll could not be found“. Even if your csproj files have correct references to other solution projects, msbuild will fail.
Maybe it appears only if project output path is outside of project directory.

It appears that Visual Studio keeps the dependencies in two ways, only one of which is read by MSBuild. I see that because I still can specify dependencies in GUI, copy solution to other machine and build it with VS in correct order.

Not with MSBuild.

The data needed by MSBuild is a “ProjectSection(ProjectDependencies) = postProject” section of SLN file. Like this:

Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "make_versioninfo", "make_versioninfo.vcproj", "{F0E0541E-F17D-430B-97C4-93ADF0DD284E}"
EndProject
Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "pythoncore", "pythoncore.vcproj", "{CF7AC3D1-E2DF-41D2-BEA6-1E2556CDEA26}"
	ProjectSection(ProjectDependencies) = postProject
		{F0E0541E-F17D-430B-97C4-93ADF0DD284E} = {F0E0541E-F17D-430B-97C4-93ADF0DD284E}
	EndProjectSection
EndProject

Note where to take the GUID of a referenced project.
If you create this section by hand, your project will build.

Not too much fun, if you have over 20 projects, where you can have up to 190 project dependencies… Have fun.

I just won a bet for $10 by solving a quiz:

Check the correctness of a braces, brackets and parentheses sequence. The solution should be of linear complexity (to say more, it’s 1-pass).

For instance, these expressions are correct: “()”, “()()[]“, “([][][]{})”, “([])()[]“, and these are not: “][", "())(", "(()".

It's basically solved in 15 lines, all others being auxiliary. Can you reproduce the algorithm?

The solution follows.

import java.security.InvalidParameterException;
import java.util.Stack;

public class Braces
{
    private static boolean isClosing(char c)
    {
        return c == ')' || c == '}' || c == ']‘;
    }

    private static boolean isOpening(char c)
    {
        return c == ‘(‘ || c == ‘{‘ || c == ‘[';
    }

    private static char matching(char c)
    {
        switch (c)
        {
        case '(': return ')';
        case '[': return ']‘;
        case ‘{‘: return ‘}’;
        case ‘)’: return ‘(‘;
        case ‘]’: return ‘[';
        case '}': return '{';
        default:
            throw new InvalidParameterException("Not a brace");
        }
    }

    public static boolean isCorrect(String expression)
    {
        Stack<Character> lastBrace = new Stack<Character>();

        for (int i=0; i<expression.length(); i++)
        {
            char c = expression.charAt(i);

            if (isClosing(c))
            {
                if (lastBrace.size() == 0) return false;
                if (lastBrace.peek().charValue() != matching(c)) return false;
                lastBrace.pop();
            }
            else if (isOpening(c))
            {
                lastBrace.push(Character.valueOf(c));
            }
            else
            {
                throw new InvalidParameterException(expression + "[" + i + "]=” + c);
            }
        }

        return lastBrace.size() == 0;
    }
}

import junit.framework.TestCase;

public class BracesTest extends TestCase {

    public void testIsCorrect()
    {
        assertTrue(Braces.isCorrect("()"));
        assertTrue(Braces.isCorrect("[]"));
        assertTrue(Braces.isCorrect("{}"));
        assertTrue(Braces.isCorrect("([])"));
        assertTrue(Braces.isCorrect("()()[]"));

        assertTrue(Braces.isCorrect("([][][]{})"));
        assertTrue(Braces.isCorrect("(()[()]())"));
        assertTrue(Braces.isCorrect("([])()[]"));

        assertFalse(Braces.isCorrect("([]"));
        assertFalse(Braces.isCorrect("[]]"));

        assertFalse(Braces.isCorrect("]["));
        assertFalse(Braces.isCorrect("(][)"));
        assertFalse(Braces.isCorrect("(][)"));

        assertFalse(Braces.isCorrect("(][)"));
        assertFalse(Braces.isCorrect("[(){}}"));

        assertFalse(Braces.isCorrect("]["));
        assertFalse(Braces.isCorrect("(("));

        assertFalse(Braces.isCorrect("(()))"));

        assertFalse(Braces.isCorrect("{}{}}{"));
    }
}

Whenever you implement own datasource for .NET GUI binding, you’lll have the choice – whether to implement IList or IListSource.

IListSource is a simplistic interface with two members: IList<T> GetList() and bool ContainsListCollection;

MSDN help about IListSource.ContainsListCollection states it’s “indicating whether the collection is a collection of IList objects”.
MSDN is not true here.

If IListSource.ContainsListCollection is false, GetList() just returns your IList.

If IListSource.ContainsListCollection is true, GetList() is expected to return ITypedList, which needs to provide a collection of PropertyDescriptor-s for every field of your collection.
Its purpose is to provide field names (including by-name field access) in runtime.

Quoted below is a code piece from a Microsoft newsgroup that resolves both cases to a data list (field values list, in second case).

And yes, if you’re planning to mutate the UI-bound collection, use IBindingList<> instead of IList<>.

static IEnumerable GetResolvedDataSource(object dataSource, string dataMember)
{
    if (dataSource != null)

    {
        IListSource source1 = dataSource as IListSource;
        if (source1 != null)

        {
            IList list1 = source1.GetList();
            if (!source1.ContainsListCollection)

            {
                return list1;
            }
            if ((list1 != null) && (list1 is ITypedList))

            {
                ITypedList list2 = (ITypedList) list1;
                PropertyDescriptorCollection collection1 = list2.GetItemProperties(new PropertyDescriptor[0]);

                if ((collection1 == null) || (collection1.Count == 0))

                {
                    throw new HttpException(HttpRuntime.FormatResourceString("ListSource_Without_DataMembers"));

                }
                PropertyDescriptor descriptor1 = null;
                if ((dataMember == null) || (dataMember.Length == 0))

                {
                    descriptor1 = collection1[0];
                }
                else

                {
                    descriptor1 = collection1.Find(dataMember, true);
                }

                if (descriptor1 != null)
                {
                    object obj1 = list1[0];

                    object obj2 = descriptor1.GetValue(obj1);
                    if ((obj2 != null) && (obj2 is IEnumerable))

                    {
                        return (IEnumerable) obj2;
                    }
                }

                throw new HttpException(HttpRuntime.FormatResourceString("ListSource_Missing_DataMember", dataMember));

            }
        }
        if (dataSource is IEnumerable)
        {
            return (IEnumerable) dataSource;

        }
    }
    return null;
}

I’m going to start with reposting my older articles written in Russian.
To be honest: It’s a self-promotion blog which has the chance to be commercial.
OTOH, this also means the articles will be carefully reviewed, filtered and refined. I promise that I’m intending to maybe do it