Familiar idioms in Perl, Python, JavaScript, and C#

When I started working on the elmcity project, I planned to use my language of choice in recent years: Python. But early on, IronPython wasn’t fully supported on Azure, so I switched to C#. Later, when IronPython became fully supported, there was really no point in switching my core roles (worker and web) to it, so I’ve proceeded in a hybrid mode. The core roles are written in C#, and a variety of auxiliary pieces are written in IronPython.

Meanwhile, I’ve been creating other auxiliary pieces in JavaScript, as will happen with any web project. The other day, at the request of a calendar curator, I used JavaScript to prototype a tag summarizer. This was so useful that I decided to make it a new feature of the service. The C# version was so strikingly similar to the JavaScript version that I just had to set them side by side for comparison:

var tagdict = new Object();

for ( i = 0; i < obj.length; i++ )
  {
  var evt = obj[i];
  if ( evt["categories"] != undefined)
    {
    var tags = evt["categories"].split(',');
    for (j = 0; j < tags.length; j++ )
      {
      var tag = tags[j];
      if ( tagdict[tag] != undefined )
        tagdict[tag]++;
      else
        tagdict[tag] = 1;
      }
    }
  }

var tagdict = new Dictionary();

foreach (var evt in es.events)
  {

  if (evt.categories != null)
    {
    var tags = evt.categories.Split(',');
    foreach (var tag in tags)
      {

      if (tagdict.ContainsKey(tag))
        tagdict[tag]++;
      else
        tagdict[tag] = 1;
      }
    }
  }

var sorted_keys = [];

for ( var tag in tagdict )
  sorted_keys.push(tag);

sorted_keys.sort(function(a,b) 
 { return tagdict[b] - tagdict[a] });

var sorted_keys = new List();

foreach (var tag in tagdict.Keys)
  sorted_keys.Add(tag);

sorted_keys.Sort( (a, b) 
  => tagdict[b].CompareTo(tagdict[a]));

The idioms involved here include:

• Splitting a string on a delimiter to produce a list

• Using a dictionary to build a concordance of strings and occurrence counts

• Sorting an array of keys by their associated occurrence counts

I first used these idioms in Perl. Later they became Python staples. Now here they are again, in both JavaScript and C#.

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