Consistent `main` throughout languages

[rradczewski]

This should help create comparable outputs between languages so the results can be cross-checked between teams. It won't be diff-able for projections where you return a data structure, but it still provides the boilerplate that teams can just add their projection to as they go through the exercise.

• c++
• clojure
• csharp
• elixir
• elm
• fsharp
• java
• js
• kotlin
• php
• python
• ruby

Example in JS

// Specify both data and projections
const DATA_SOURCES = ["../data/0.json", "../data/2.json"];
const PROJECTIONS = {
  eventCounter: require("./eventCounter"),
  registeredPlayers: require("./registeredPlayers")
}

const dataSets = DATA_SOURCES.reduce(
  (dataSets, source) => Object.assign({}, dataSets, { [source]: require(source) }), 
  {});

for(let projection in PROJECTIONS) {
  for(let dataSet in dataSets) {
    const result = PROJECTIONS[projection](dataSets[dataSet]);
    console.log(`${projection}\t${dataSet}\t${JSON.stringify(result)};
  }
}

Example output

eventCounter	0.json	4
eventCounter	1.json	30
eventCounter	2.json	43727
eventCounter	5_2015_01_2017_01.json	104712
eventCounter	10_2015_01_2016_01.json	48960
numberOfRegisteredPlayers	0.json	1
numberOfRegisteredPlayers	1.json	2
numberOfRegisteredPlayers	2.json	218
numberOfRegisteredPlayers	5_2015_01_2017_01.json	158
numberOfRegisteredPlayers	10_2015_01_2016_01.json	254
numberOfRegisteredPlayersByMonth	0.json	{"2016-09":1}
numberOfRegisteredPlayersByMonth	1.json	{"2016-05":2}
numberOfRegisteredPlayersByMonth	2.json	{"2016-04":2,"2016-05":1,"2016-06":8,"2016-07":16,"2016-08":27,"2016-09":64,"2016-10":52,"2016-11":28,"2016-12":16,"2017-01":3,"2017-03":1}
numberOfRegisteredPlayersByMonth	5_2015_01_2017_01.json	{"2015-01":5,"2015-02":5,"2015-03":5,"2015-04":6,"2015-05":6,"2015-06":4,"2015-07":5,"2015-08":6,"2015-09":3,"2015-10":5,"2015-11":8,"2015-12":12,"2016-01":8,"2016-02":8,"2016-03":10,"2016-04":11,"2016-05":12,"2016-06":9,"2016-07":6,"2016-08":5,"2016-09":6,"2016-10":5,"2016-11":8}
numberOfRegisteredPlayersByMonth	10_2015_01_2016_01.json	{"2015-03":26,"2015-04":24,"2015-05":12,"2015-06":25,"2015-07":18,"2015-08":20,"2015-09":30,"2015-10":22,"2015-11":25,"2015-12":52}

[tcoopman]

I have to think about this one a bit. I feel it already adds too much. For us part of the goal of the workshop was that participants don't have to struggle with the boilerplate.
Comparable outputs would help, but consistent main methods might not help that much. We could add some unified tests though.