ludic/packages/ludic.vehicles/README.md

ludic.vehicles

Each player's boat and horse: called to one of four berths off a pier head or four bays at a trough, made there the first time and fetched there after, owned by one player and ridden by one at a time, ridden over water or land, and got off onto a spot the rider's own safe-spot rule found. Uses ludic.base and nothing else.

import "ludic.vehicles"

The package never draws, prices or words anything. A game draws a vehicle when VehicleWorld.made says one exists and moves its model on placed; it charges for a hire and says the words; and it binds the rider to its walking body (in Maroon Lake, ludic.character through the game).

The rules it keeps

• A kind's numbers are the game's data. The package keeps the rules (a walk and a gallop on stamina, a stroke and a turn, where a rider gets off) and no numbers: the game hands each kind a VehicleSpec with vehicles_spec(kind, spec) - in Maroon Lake from its VehicleKinds table - once, before any vehicle is made. A kind with no spec cannot be called; a reset keeps the specs.

• Nothing is parked for anyone. A vehicle has an owner and a rider; vehicle_find(kind) is this player's own and nothing else may pick "the" boat. A place is taken while a boat lies in it or a horse is tied at it (home_x, home_z), within half a place's spacing.

• Where a body is put down is one question with one answer. Getting off asks the rider's safe_spot - a wade of up to the spec's off_depth within its search from a boat, off_side out by the right flank from a horse - and a boat too far out refuses and says so (VEHICLE_NO_LANDING) rather than dropping the rider in the lake.

• A boat is a body in the game's physics (VehicleHull, phase 16; a buoyant Jolt hull in Maroon Lake). The package rows it - the stick forward and back is a stroke along the bow, left and right the oars pulled against each other - and reads back where the hull is and how fast it goes. The water floats it, the wind (VehicleWorld.wind) drifts a rowed boat, and the lake bed stops it at the shore. A boat nobody rows is moored where it was called or left (home_x, home_z, home_yaw): its hull is put back there whenever it strays, so it never crosses the lake alone; the swell at the sail limit takes the outward share of a stroke.

• A horse walks on legs in the game's physics (VehicleLegs; a Jolt walker in Maroon Lake). The package decides its pace - a walk, a canter on stamina, hay for every metre - and never steps it into water; the legs meet the ground, its steps and slopes, and whatever stands in its way. What they cover along its heading is its speed, so a fence brings it to a stand and a trunk it glances pushes it aside. A horse called to its bay or led round where it is tied is stood there (stand).

• A horse's steering follows signed speed: backing up with the stick left swings the nose right.

• A stale rider locks a vehicle for ever, so getting off is vehicle_dismount or vehicle_drop.

The ports

VehicleHull { put(nid, x, y, z, yaw), row(nid, forward, turn), drift(nid, fx, fz), read(nid) -> bool, x, y, z, yaw, speed, gone(nid) } is required: the boat's body, named by the vehicle's nid. VehicleLegs { walk(nid, x, y, z, vx, vz, dt) -> bool, x, y, z, stand(nid, x, y, z), gone(nid) } is the horse's: unbound, the ground is walked as it is and only a rise steeper than it can take stops it.

export port VehicleWorld {
  ground: fn(float, float) -> float                       # required
  water: fn(float, float) -> float                        # the surface (unbound: never wet)
  swell: fn(float, float, float, float) -> float          # (x, z, fx, fz): a stroke's share lost
  wind: fn() -> float                                     # 0..1
  wind_yaw: fn() -> float                                 # the yaw the wind pushes toward
  next_id: fn() -> int                                    # an id across machines
  made: fn(Vehicle) -> void                               # draw it
  placed: fn(Vehicle) -> void                             # move its model
  gone: fn(Vehicle) -> void                               # its owner left
}
export port VehicleRider {
  board(x, z, yaw), ride_at(x, y, z, yaw, speed), step_off(x, z),
  safe_spot(x, z, from_y, max_depth) -> bool, safe_x(), safe_z()
}

API

VEHICLE_HORSE, VEHICLE_BOAT, VEHICLE_PLACES, VEHICLE_KINDS	the kinds, four places each, and how many kinds may have a spec
VehicleSpec { seat_h, walk, run, acc, turn, row, row_turn, wind, hay_per_m, hay_min, run_min, tire_at, tire, rest, off_side, off_depth }	a kind's numbers: the seat, a horse's pace, stamina and hay, a boat's oars and wind, where one gets off
vehicles_spec(kind, spec), vehicle_spec(kind)	set a kind's numbers (at boot), and ask them
Vehicle { kind, nid, x, y, z, yaw, speed, fuel, food, seat_h, owned, owner, rider, home_x, home_z }	a vehicle (change one through the verbs)
vehicles_dock_at(x, z, yaw), vehicles_rail_at(x, z, yaw), vehicles_dock_yaw()	where the places are measured from
vehicle_berth_x/z(k), vehicle_post_x/z(k), vehicle_bay_x/z(k), vehicle_place_x/z(kind, k)	the places
vehicle_call_for(pid, kind, k) -> bool, vehicle_in_place(kind, k), vehicle_free_place(kind), vehicle_mine_in_place(kind)	calling one to a place
vehicle_of(pid, kind), vehicle_find(kind), vehicle_nearest(x, z, reach), vehicles_all(), vehicle_current(), vehicle_ride_kind()	questions
vehicle_mount(v) -> bool, vehicle_dismount() -> bool, vehicle_drop()	on and off
vehicle_update(ix, iz, run, dt)	a frame of riding from the rider's stick (bind it where the body hands its stick over)
vehicle_own(v), vehicle_feed(v, hay), vehicle_follow(v, x, y, z, yaw), vehicles_release(pid), vehicle_restore(kind, owned, food)	hiring, hay, a tied horse's wandering, a player leaving, a saved word
vehicles_tick(dt)	every boat's hull read back: a rowed one pushed by the wind, one nobody rows held at its mooring (the game calls it where the world is run)
vehicle_facts() -> Queue<VehicleFact>	{ what, nid, kind, owner, x, z, v }: VEHICLE_MOUNTED, _DISMOUNTED, _NO_LANDING, _MOVED (v: metres), _SWELL (every 14 s), _HUNGRY, _FED
vehicles_reset(), vehicles_system() -> System	"vehicles": this player's own saved by kind (hired, hay) - where they lie is not saved

Tests

ludic test packages/ludic.vehicles

A fake shore with a pier head and a trough, and Maroon Lake's numbers as the specs: a kind with no spec refused and a spec's walk and seat obeyed, berths and bays, calling and fetching, a taken place, a player leaving, a hungry horse, riding a horse into a trunk and to the water's edge; a real Jolt hull rowed out, losing its stroke to the swell, turned, stopped by the shore's bed and drifted by the wind; getting off near a shore and far from one, and the save.