ludic/examples/lib/combat.ludic

# ============================================================================
# combat.ludic — a Ludic *library*, not a game.
#
# `module` instead of `game` means: no entry point, no frame loop. ludicc
# compiles this to a real shared object —
#
#     ludicc examples/lib/combat.ludic --shared -o build/libcombat.dylib
#
# — whose `export fn`s are ordinary C-ABI symbols. Anything that can call a
# .dylib/.so/.dll can call these: another Ludic program via `extern fn`, a game
# engine, a test harness, a scripting host. Non-exported functions stay private
# to the library.
# ============================================================================
program Combat {

  const CRIT_MULT: int = 2

  # damage after armour, with a crit multiplier applied on an exact roll
  @export fn damage(attack: int, armour: int, roll: int) -> int {
    let raw = attack - armour
    if raw < 1 { raw = 1 }
    if roll == 20 { raw = raw * CRIT_MULT }
    return raw
  }

  # how many hits to drop a target — the loop is here so the caller cannot
  # accidentally disagree with `damage` about rounding
  @export fn hits_to_kill(hp: int, attack: int, armour: int) -> int {
    let left = hp
    let n = 0
    while left > 0 {
      left = left - damage(attack, armour, 0)
      n = n + 1
    }
    return n
  }

  @export fn xp_for(level: int, kills: int) -> int {
    return curve(level) * kills
  }

  # private: not exported, so it is not a symbol in the library
  fn curve(level: int) -> int {
    return 10 + level * level * 3
  }
}