Update config.json to match new specification

[kytrinyx]

For the past three years, the ordering of exercises has been done based on gut feelings and wild guesses. As a result, the progression of the exercises has been somewhat haphazard.

In the past few months maintainers of several tracks have invested a great deal of time in analyzing what concepts various exercises require, and then reordering the tracks as a result of that analysis.

It would be useful to bake this data into the track configuration so that we can adjust it over time as we learn more about each exercise.

To this end, we've decided to add a new key exercises in the config.json file, and deprecate the problems key.

See exercism/discussions#60 for details about this decision.

Note that we will not be removing the problems key at this time, as this would break the website and a number of tools.

The process for deprecating the old problems array will be:

• Update all of the track configs to contain the new exercises key, with whatever data we have.
• Simultaneously change the website and tools to support both formats.
• Once all of the tracks have added the exercises key, remove support for the old key in the site and tools.
• Remove the old key from all of the track configs.

In the new format, each exercise is a JSON object with three properties:

• slug: the identifier of the exercise
• difficulty: a number from 1 to 10 where 1 is the easiest and 10 is the most difficult
• topics: an array of strings describing topics relevant to the exercise. We maintain a list of common topics at https://github.com/exercism/x-common/blob/master/TOPICS.txt. Do not feel like you need to restrict yourself to this list; it's only there so that we don't end up with 20 variations on the same topic. Each language is different, and there will likely be topics specific to each language that will not make it onto the list.

The difficulty rating can be a very rough estimate.

The topics array can be empty if this analysis has not yet been done.

Example:

"exercises": [
  {
    "slug": "hello-world" ,
    "difficulty": 1,
    "topics": [
        "control-flow (if-statements)",
        "optional values",
        "text formatting"
    ]
  },
  {
    "difficulty": 3,
    "slug": "anagram",
    "topics": [
        "strings",
        "filtering"
    ]
  },
  {
    "difficulty": 10,
    "slug": "forth",
    "topics": [
        "parsing",
        "transforming",
        "stacks"
    ]
  }
]

It may be worth making the change in several passes:

• [x] Add the exercises key with the array of objects, where difficulty is 1 and topics is empty.
• [ ] Update the difficulty settings to reflect a more accurate guess.
• [ ] Add topics (perhaps one-by-one, in separate pull requests, in order to have useful discussions about each exercise).

[yurrriq]

/cc @skovsgaard

[skovsgaard]

@yurrriq, so far I haven't encountered problems with any of this but I'm very early in the task set.

One thing I can help with is what we talked about regarding learning curve. I figure I can make a note of each task's perceived difficulty as I work my way through them to just sort of give a rough estimate from someone seeing them for the first time.

[yurrriq]

That would be awesome! I'm not sure if this update has to be done at all at once. If not, it could be good to do it exercise by exercise as you progress. I can try to give feedback or make some guesses at some point, but I'm not sure I'd be the best judge. If xerlang has done it or xlisp, we might take some cues from them.

[yurrriq]

Ah, it looks like an iterative approach is outlined above.