Small enhancement to Character Modifiers

[dseguin]

Summary

None

Purpose of change

Minor enhancement to #53069.
JSONify the fall damage and slip prevention modifiers added in #54555.

Describe the solution

Add the ability to define an array of limb scores affecting a character modifier (as well as a combo operation, either ADD or MULT).

{
  "type": "character_mod",
  "id": "limb_fall_mod",
  "description": "Fall damage modifier",
  "mod_type": "x",
  "value": { "limb_score": [ "move_speed", "footing", "reaction" ], "limb_score_op": "x" }
}

Also add the ability to specify a weighted list (with a custom denominator):

{
  "type": "character_mod",
  "id": "slip_prevent_mod",
  "description": "Slip prevention modifier",
  "mod_type": "x",
  "value": {
    "limb_score": [ [ "grip", 3.0 ], [ "lift", 2.0 ], "footing" ],
    "override_encumb": true,
    "limb_score_op": "+",
    "denominator": 6.0
  }
}

Describe alternatives you've considered

I get the impression that JSON is not very friendly to arbitrary arithmetic :P

Testing

Added test cases to check that added/multiplied limb scores in character modifiers are correctly calculated:

./tests/cata_test -d yes --rng-seed time "Multi-limbscore modifiers"

Additional context

Ping: @Venera3

[PatrikLundell]

It requires a fair bit of guesswork to figure out that 'x' is supposed to mean multiplication (in the snipped in the post: the code seems to use the only marginally better '"'), assuming I guessed correctly... I would suggest to let the strings contain words, or at least abbreviations of words, such as "ADD", "MULT", etc.

JSON is actively hostile to anything that requires documentation...

[Zireael07]

IIRC Cata devs managed to inject comments into JSON via some hack or other - this is a case of something that needs a comment.

[PatrikLundell]

On the comment tangent: It works to add "data" elements with names of "//", "//1", etc. followed by the documentation string in at least some places (I've used it with construction recipes). I suspect anything starting with double slashes are left unmatched against the actual pattern the JSON parsing is looking for. It's a shame the nutjob creating JSON threw out support for actual comments in a rage fit over perceived misuse of comments as processing directives by someone, though.

[Venera3]

Sweet! Now, this probably counts as "arbitrary arithmetic", but do you think weighted averages would be doable? Slipping down uses (game.cpp:11970ish)

    slip /= ( u.get_limb_score( limb_score_grip ) * 3 + u.get_limb_score(
                  limb_score_lift, body_part_type::type::num_types,
                  1 ) * 2 + u.get_limb_score( limb_score_footing ) ) / 6;

to make gripping more important than the rest. It's not a big thing if it's more trouble than it's worth, addition/multiplication already covers a lot of the bases.

[dseguin]

I guess I have more work to do :P

But really, it shouldn't be too hard to implement weighted lists. I'll add that to these changes.