Implement D&D Character exercise

[BNAndras]

This will need an instruction append to explain some of the basics of a data declaration.

[BNAndras]

I also forgot my name in the config.json. Whoops

[BNAndras]

Right, I'm reconsidering this one already because we're requiring them to create an empty Character and then initialize it. They could solve this by defining a character function that returns an object expression with the field values already populated. We're not playing to the strengths of having a named type here like using the type detectors so I think it'd be easier to forgo it. Clock could be my data declaration exercise instead. :)

modifier = lam(value): num-floor((value - 10) / 2) end
ability = lam():
    roll-dice = lam(_): num-random(5) + 1 end
    rolls = map(roll-dice, repeat(4, 0))
    rolls.sort().drop(1).foldl(lam(elt, acc): elt + acc end, 0)
end

fun character():
  cached_constitution = ability()
  {
    strength: ability(),
    dexterity: ability(),
    constitution: cached_constitution,
    intelligence: ability(),
    wisdom: ability(),
    charisma: ability(),
    hitpoints: modifier(cached_constitution)
  }
end

character() #  {strength: 11, dexterity: 9, constitution: 9,  intelligence: 7,  wisdom: 14,  charisma: 15,  hitpoints: -1}