Explain generic types and add DebugLevel to Player

This simulation engine is intended for people who are interested in game design, not computer programming -- the engine wants to do all the engine stuff so the simulation can be implemented with less familiarity with the language. Generics, however, are not widely regarded as a "new programmer" thing -- even though they're surprisingly familiar, in the end  (slice-of-T, map-from-K-to-V). So a long comment explaining a bit about what's going on seems warranted.
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Kistaro Windrider 2023-04-01 13:32:25 -07:00
parent 7f8dcd63d6
commit b324a39918
Signed by: kistaro
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@ -2,7 +2,55 @@ package cardsim
import "math/rand" import "math/rand"
// Player stores all gameplay state for one player. // Player stores all gameplay state for one player at a specific point in time.
// Game-specific data is stored in Stats.
//
// Player is a generic type -- see https://go.dev/blog/intro-generics for more
// information on how these work. Think of "Player" as a "type of type" --
// when you create one, you tell it what kind of data it needs to keep for
// the simulation itself, and each Player that works with a different kind of
// data is a different kind of Player and the compiler will help you with that.
// This is the same idea as "slice of something" or "map from something to
// something" -- different kinds of Players are different from each other and
// "know" what type of data they use, so the compiler can tell you if you're
// using the wrong type.
//
// Generic types have to use a placeholder to represent the type (or types --
// consider maps, which have both keys and values) that will be more specific
// when the type is actually used. They're called "type parameters", like
// function parameters, because they're the same kind of idea. A function puts
// its parameters into variables so you can write a function that works with
// whatever data it gets; a generic type takes type parameters and represents
// them with type placeholders so you can write a *type* that works with
// whatever specific other types it gets.
//
// Just like function parameters have a type that says what kind of data the
// function works with, type parameters have a "type constraint" that says what
// kind of types the generic type works with. Go already has a familiar way
// to express the idea of "what a type has to do": `interface`. In Go, type
// constraints are just interfaces.
//
// But wait, why use generics at all? Can't we just use an interface in the
// normal way instead of doing this thing? Well, yes, we could, but then the
// compiler doesn't know that the "real types" for things matching these
// interfaces all have to actually be the same type. The compiler will stop
// you from putting an `Orange` into a `[]Apple`, but it wouldn't stop you from
// putting a `Fruit` into a `[]Fruit` because, well, of course it wouldn't,
// they're the same type.
//
// Different simulation games made with `cardsim` are different. Rules made for
// simulating the economy of a kobold colony and mine wouldn't work at all with
// data for a simulation about three flocks of otter-gryphons having a
// territory conflict over a river full of fish. By using generics, the compiler
// can recognize functions and data and types intended for different simulation
// games and prevent you from using the wrong one, when it wouldn't be able to
// if all this stuff was written for "some simulation game, don't care what".
//
// Generic interfaces (like `Card[C]`, `Rule[C]`, `InfoPanel[C]`, and more)
// don't mean you have to write generics of your own. It's exactly the opposite!
// Because the interface has this extra type in it, you only need to implement
// the specific kind of interface that works with your game. There's more detail
// on this in the comment on `Rule[C]`.
type Player[C StatsCollection] struct { type Player[C StatsCollection] struct {
Stats C Stats C
Name string Name string
@ -19,4 +67,6 @@ type Player[C StatsCollection] struct {
Turn int Turn int
TemporaryMessages []Message TemporaryMessages []Message
TemporaryPanels []InfoPanel[C] TemporaryPanels []InfoPanel[C]
DebugLevel int
} }