diff --git a/INTERFACE_ANALYSIS.md b/INTERFACE_ANALYSIS.md deleted file mode 100644 index 28a2bf5..0000000 --- a/INTERFACE_ANALYSIS.md +++ /dev/null @@ -1,643 +0,0 @@ -# Designing an Idiomatic API Interface - -- [Designing an Idiomatic API Interface](#designing-an-idiomatic-api-interface) - - [Current State](#current-state) - - [Interface of the Built-in Map](#interface-of-the-built-in-map) - - [Interface of `go-cuckoo`](#interface-of-go-cuckoo) - - [Determining Congruency](#determining-congruency) - - [Determining Familiarity](#determining-familiarity) - - [Target State](#target-state) - - [Solving Congruency](#solving-congruency) - -We (the maintainers) built `go-cuckoo`'s API interface without design intent. -Up until now, we paid more attention implementing the underlying functionality of the cuckoo hashing. - -With the fundamentals of the algorithm built, we should revisit the interface. -It should align closer to the following principles: - -- **Congruency** - A `go-cuckoo` table should have the same core functionality as Go's built-in map. - -- **Familiarity** - A `go-cuckoo` table should behave similarly to Go's standard map, so users will intuitively know how to use it. - In effect, its users will carry less cognitive load. - -## Current State - -### Interface of the Built-in Map - -Listed below is every interface provided by Go to the built-in map object. -Also included, are the functions from the package `maps` in the standard library. - -
-Interfaces - -| # | Built-in Interface | Description | -| --- | ---------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------- | -| 1 | `m := make(map[K]V)` | Returns an empty map using the built-in `make()` function. | -| 2 | `m := make(map[K]V, hint)` | Returns an empty map using `make()`, with a capacity 'hint'. This hint is how many items the map expects to hold, _not_ a measure of how large it is. | -| 3 | `m := map[K]V{...}` | Returns a map, which may be filled with entries in the ellipsis (optional). | -| 4 | `var m map[K]V` | Defines an empty _variable_ that holds a map. This differs from #1 because `m` is uninitialized (nil) here. | -| 5 | `m[k] := v` | Assigns the value of `k` to `v`. | -| 6 | `v := m[k]` | Returns the value of `k` if it exists. Otherwise, `v` is uninitialized. | -| 7 | `v, ok := m[k]` | Similar to #6, except `ok` is equal to whether `v` is initialized. This is comma-ok notation. | -| 8 | `for k, v := range m` | Iterates over every key-value pair in `m`. The order is random. | -| 9 | `delete(m, k)` | Unassigns the value `k`. Returns no value. | -| 10 | `clear(m)` | Unassigns all keys in `m`. Returns no value. | -| 11 | `n := len(m)` | Returns the number of entries in `m`. If nil, `m` returns 0. | -| 12 | `m2 := maps.Clone(m)` | Returns a copy of `m`. | -| 13 | `maps.Copy(dst, src)` | Assigns every entry of `src` in `dst`. | -| 14 | `ok := maps.Equal(m1, m2)` | Returns true iff `m1` and `m2` the same entries. | -| 15 | `ok := maps.EqualFunc(m1, m2, fn)` | Like #14, but with a custom comparator for non-comparable values. | -| 16 | `maps.DeleteFunc(m, fn)` | Removes every entry in `m` which satisfies `fn`. Returns no value. | -| 17 | `it2 := maps.All(m)` | Returns an 2D iterator over every key-value pair. | -| 18 | `it := maps.Keys(m)` | Returns an iterator over every key. | -| 19 | `it := maps.Values(m)` | Returns an iterator over every value. There can be duplicates. | -| 20 | `m := maps.Collect(seq)` | Returns a map, with every entry defined in a 2D iterator over key-value pairs. | -| 21 | `maps.Insert(m, seq)` | Assigns to `m` all key-value pairs in 2D iterator `seq`. Returns no value. | - -
- -### Interface of `go-cuckoo` - -On the other hand, here is the current contract for `go-cuckoo`. - -
-Interfaces - -| # | `go-cuckoo` Interface | Description | -| --- | -------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------- | -| 1 | `m := New(opts...)` | Creates a table using the default hash and equal function. The options configure its behavior. Confined to comparable keys. | -| 2 | `m := NewBy(keyFunc, opts...)` | Like #1, but allows any key type. A `keyFunc` is used to derive a comparable key. | -| 3 | `m := NewCustom(hashA, hashB, equalFunc, opts...)` | Like #1, but allows control over the hashes used to allow any key type. An `equalFunc` determines key equality. | -| 4 | `seq := m.Entries()` | Returns an unordered 2D iterator of all key-value pairs in the table. | -| 5 | `v := m.Find(k)` | Removes the value for `k`. Returns true if `k` existed. | -| 6 | `v, ok := m.Get(k)` | Returns the value for `k` in the table. Also, returns true if the `k` exists, otherwise false. When false, `v` is undefined. | -| 7 | `ok := m.Has(k)` | Returns true if `k` is in the table. | -| 8 | `err := m.Put(k, v)` | Sets value `v` for key `k`. Otherwise, returns error. | -| 9 | `n := m.Size()` | Returns the number of items in `m`. | -| 10 | `str := m.String()` | Returns `m` as a string in the format "table[k1:v1 k2:v2 ...]". | -| 11 | `cap := m.TotalCapacity()` | Returns how many slots `m` has allocated. | -| 12 | `ok := m.Drop(k)` | Removes `k` from the table. Returns whether the key had existed. | - -
- -### Determining Congruency - -So, how does the core functionality compare? -Listed below is an analysis of every interface in Go's standard map. -Each is compared against what `go-cuckoo` offers, and categorized into the following groups: - -- ✅ Covered: an analog exists. -- ⚠️ Partial: workaround available. -- ❌ Gap: no analog yet; addressed in [Target State](#solving-congruency). - -Specifically, here we are checking for functionality. -Is there functionality that this offers which `go-cuckoo` does not? -We are checking accessibility, but not discoverability. -The latter will be considered later. - -
-✅ m := make(map[K]V) - -The analog is `m := New()`. - -
- -
-⚠️ m := make(map[K]V, hint) - -This has no simple analog. - -It is close to `m := New(Capacity(hint))`, but it assigns starting capacity, not expected size. -For the built-in map, these are two separate things. - -- Capacity is an internal measure, used to optimize space/speed. - It is hidden from the user because it depends on the underlying implementation, which may change. -- Expected size requires the map must hold a number of items before resizing. - This is tangeable and agnostic to implementation, hence why it is given to the user. - -In short, this interface defines expected size, but `Capacity()` defines capacity. - -
- -
-❌ m := map[K]V{...} - -This has no simple analog, the closest being: - -```go -m := New[K, V]() -for k, v := range startingEntries { - m.Put(k, v) -} -``` - -It is idiomatic, but far less ergonomic. - -
- -
-✅ var m map[K]V - -The analog is `var m Table[K, V]`. - -
- -
-✅ m[k] := v - -The analog is `err := m.Put(k, v)`. - -
- -
-✅ v := m[k] - -The analog is `v := m.Find(k)`. - -
- -
-✅ v, ok := m[k] - -The analog is `v, ok := m.Get(k)`. - -
- -
-✅ for k, v := range m - -The analog is `for k, v := range m.Entries()`. - -
- -
-✅ delete(m, k) - -The analog is `ok := m.Drop(k)`. - -
- -
-❌ clear(m) - -There is no analog. - -The easiest may to do this is to delete all items individually: - -```go -for k := range m.Entries() { - m.Drop(k) -} -``` - -
- -
-✅ n := len(m) - -The analog is `n := m.Size()`. - -
- -
-❌ m2 := maps.Clone(m) - -There is no analog. - -The easiest way to do this currently is to make a new map, and manually add the items. - -```go -m2 := cuckoo.Table[K, V]() - -for k, v := range m.Entries() { - m2.Put(k, v) -} -``` - -This gets complicated by the various options available to the user. -Furthermore, any custom `EqualFunc`, `keyFunc` or `Hash` is not transferred. - -
- -
-❌ maps.Copy(dst, src) - -There is no analog. - -The simplest way to do this is with a for-loop. - -```go -for k, v := range src.Entries() { - dst.Put(k, v) -} -``` - -
- -
-❌ ok := maps.Equal(m1, m2) - -There is no analog. - -Users have to manually check the key-value pairs to determine equality. - -
- -
-❌ ok := maps.EqualFunc(m1, m2, fn) - -There is no analog. - -Users have to manually check the key-value pairs to determine equality. - -
- -
-❌ maps.DeleteFunc(m, fn) - -There is no analog. - -Users have to manually delete keys. - -
- -
-✅ it2 := maps.All(m) - -The analog is `it2 := m.Entries()`. - -
- -
-⚠️ it := maps.Keys(m) - -There is no simple analog. - -A close neighbor is `it2 := m.Entries()`. -Users can use this in a for-loop, and pick out just the keys: - -```go -for k := range m.Entries() { - // ... -} -``` - -
- -
-⚠️ it := maps.Values(m) - -There is no simple analog. - -A close neighbor is `it2 := m.Entries()`. -Users can use this in a for-loop, and pick out just the values: - -```go -for _, v := range m.Entries() { - // ... -} -``` - -
- -
-❌ m := maps.Collect(seq) - -There is no analog. - -
- -
-❌ maps.Insert(m, seq) - -There is no analog. - -
- -### Determining Familiarity - -We can categorize all existing table functionality by each interface's familiarity: - -- ✅ Idiomatic: is clear, intuitive, and easily understood. -- ❌ Non-idiomatic: is misleading; addressed in [Target State](#solving-congruency). - -
-✅ m := New(opts...) - -Criteria: - -Noun/adjective form — Go constructors use NewX where X is a noun or adjective, not a verb or past participle (NewReaderSize, not NewSized) -Names what the user provides — the suffix should hint at the distinguishing parameter (NewBufferString tells you it takes a string) -Progression is readable — the three names together should imply simple → intermediate → advanced -Not misleadingly generic — NewWith or NewConfig could mean anything - -
- -
-m := NewBy(keyFunc, opts...) - -- Use `NewKeyed()`. - -
- -
-m := NewCustom(hashA, hashB, equalFunc, opts...) - -- Use `NewHashed()`. - -
- -
-❌ seq := m.Entries() - -- Call it `All()`. - -
- -
-v := m.Find(k) - -- Call it `m.Lookup()`. The name `m.Find` implies a search algorithm. - -
- -
-v, ok := m.Get(k) - -
- -
-ok := m.Has(k) - -
- -
-❌ err := m.Put(k, v) - -- Call it `Set()`. -- No built-in library consensus, but 3rd party packages prefer `Set()`. - -
- -
-❌ n := m.Size() - -- Call it `Len()`. -- Size is a Java idiom. - -
- -
-✅ str := m.String() - -
- -
-❌ cap := m.TotalCapacity() - -- Remove. This is an implementation detail. - -
- -
-❌ ok := m.Drop(k) - -- Call it `Delete()`. - -
- -## Target State - -### Solving Congruency - -We should make the following changes to accomodate for congruency: - -
-ok := maps.EqualFunc(m1, m2, fn) - -We should implement a new function: - -```go -func EqualFunc[K, V1, V2 any](t1 *Table[K, V1], t2 *Table[K, V2], eq func(V1, V2) bool) bool -``` - -This function is free, and not bound as a receiver function. -(It is called `cuckoo.Equal(t1, t2)`, not `t1.Equals(t2)`.) -The latter implies `t1` has authority, when in fact neither do. - -We define equality as: - -1. Neither table has a key the other doesn't. -2. Each key has the same value in each table. - Parameter `eq` determines this equality. - -Custom `EqualFunc`'s complicate this, as they modulate key identity in tables. -If two tables may differ on whether two keys are different, this function might break. -So, we must assume that: - -- Both tables have `EqualFunc`'s which 'agree' on the identity of the keys present in the tables. - Agreement is defined as: if two keys are distinct in one table, they are distinct in the other. - -The name `EqualFunc` is already taken by `EqualFunc[K, V]`: an alias for `func(a, b K) bool`. -Inlining `EqualFunc[K, V]` would solve this problem. -We will move the documentation attached to it to `DefaultEqualFunc`. - -
- -
-ok := maps.Equal(m1, m2) - -We should implement a new function, to conform with the standard library: - -```go -func Equal[K any, V comparable](t1, t2 *Table[K, V]) bool -``` - -It uses the same equality check as in `EqualFunc`. -Once again, the function is free because it is symmetric. - -
- -
-maps.Insert(m, seq) - -We should implement a new receiver for the table: - -```go -func (t *Table[K, V]) Insert(seq iter.Seq2[K, V]) error -``` - -A receiver fits better even though `maps.Insert` is a free function, because copying it is asymmetric. -Map `dst` receives entries from map `src`. -It's only free because Go's standard map is built into the language, and so cannot have receivers. - -In terms of naming, `t.Extend` is more accurate, and has precedent in [Python](docs.python.org/3/tutorial/datastructures.html#more-on-lists) and [Rust](https://doc.rust-lang.org/std/iter/trait.Extend.html). -When [adding iterator function](https://github.com/golang/go/issues/61900) to the `maps` package, the Go team chose to frame it as 'sources' and 'sinks'. -With this model, `maps.Insert` made more sense than `maps.Extend`. -Ultimately, `t.Insert()` is a better choice to be consistent with `maps`. - -
- -
-maps.Copy(dst, src) - -We should implement a new receiver for the table: - -```go -func (t *Table[K, V]) Copy(src *Table[K, V]) error -``` - -It's functionality should match that of `t.Insert()`. - -A receiver fits better even though `maps.Copy` is a free function, 'copying' it is asymmetric: `dst` is writen into by `src`. -It is only free because Go's standard map is built into the language, and so cannot have receivers. - -The name `t.Merge()` might be more accurate, but it does work because: - -- `t.Copy()` matches Go's built-in `copy()`, and `io.Copy()`. The Go team used [the same logic](https://github.com/golang/go/discussions/47330#discussioncomment-1167799) to name `maps.Copy()`. - In this case, `t.Merge()` would be an outlier. -- `t.Merge()` implies some sort of conflict-resolution, when there is not. - It simply overwrites the values. - -
- -
-maps.DeleteFunc(m, fn) - -We should implement a new receiver for the table: - -```go -func (t *Table[K, V]) DeleteFunc(del func(K, V) bool) -``` - -It would have the same functionality as `maps.DeleteFunc`. - -A free function could work here, but `t` has clear authority over `del`. -Other than being consistent with the `maps` package, `t.DeleteFunc` follows the Go convention of appending `Func` to higher-order equivalents of functions. -This trumps names like `t.DeleteIf`, which lend more to [Java](https://docs.oracle.com/javase/8/docs/api/java/util/ArrayList.html#removeIf-java.util.function.Predicate-) or [C++](https://en.cppreference.com/cpp/algorithm/remove). -The word `Delete` is also convention, tying back to the built-in `delete()`. - -
- -
-m := maps.Collect(seq) - -We should implement a new constructor. - -```go -func Collect[K comparable, V any](seq iter.Seq2[K, V]) (*Table[K, V], error) -``` - -It would create a `New()` table, and insert all entries in `seq`. - -This reveicer only supports the standard table constructor, with comparable keys. -It is tempting to add `CollectBy` or `CollectCustom` to support all table types, but doing so would pollute the public interface. - -It would be just one more line to initialize the table and then call `t.Insert` directly: - -```go -t := // ... -err := t.Insert(seq) -``` - -
- -
-m := map[K]V{...} - -We should make a new constructor, because entries are generic. -So, creating an option with inialized entries doesn't work. - -With the previous additions, users have a few options. -If they want to use a `New()` table, `t.Collect` matches well: - -```go -t, err := cuckoo.Collect(func(yield func(K, V) bool) { - yield(key1, val1) - yield(key2, val2) -}) -``` - -For `NewCustom()` or `NewBy()` tables, users can call `t.Insert` after initialization: - -```go -t := // ... -err := t.Insert(func(yield func(K, V) bool) { - yield(key1, val1) - yield(key2, val2) -}) -``` - -It is one more line. -But, the alternative is polluting the public interface with corresponding `*WithEntries` constuctors. - -
- -
-m := make(map[K]V, hint) - -We should add a new option: - -```go -func ExpectedSize(n int) Option -``` - -When fed to a table, it will allocate enough space to hold `n` entries without a resize. - -
- -
-clear(m) - -We should implement a new receiver: - -```go -func (t *Table[K, V]) Clear() -``` - -It will remove all entries from the table. - -
- -
-m2 := maps.Clone(m) - -We should implement a matching function: - -```go -func (t *Table[K, V]) Clone() *Table[K, V] -``` - -Also, it will copy the hash, equality function, and options used in the table. - -
- -
-it := maps.Keys(m) - -We should implement a matching function: - -```go -func (t *Table[K, V]) Keys() iter.Seq[K] -``` - -It is tempting to just have `All()`, but it returns a `Seq2`, not a `Seq`. -There is no iterator adaptor between `Seq` and `Seq2`, and will not be for the foreseeable future. -This function, while it feels superfluous, is required. - -
- -
-it := maps.Values(m) - -We should implement a matching function: - -```go -func (t *Table[K, V]) Values() iter.Seq[V] -``` - -For the same reason we need `Keys()`, we also need `Values()`. - -