diff --git a/adr/001_interface_design.md b/adr/001_interface_design.md new file mode 100644 index 0000000..7afe20a --- /dev/null +++ b/adr/001_interface_design.md @@ -0,0 +1,217 @@ +# Designing an Idiomatic Interface + +Currently, the contract for package was built without design. +More attention was paid to implementing the underlying functionality of the cuckoo hashing. + +With the fundamentals of the algorithm built, our API contract should be revisited. +It should align closer to the following principles: + +- **Similarity to the builtin map.** + If our cuckoo table behaves similarly to Go's standard map, our user will intuitively know how to use it. + This lowers the cognitive load our developers must carry. + +## Current State + +### Interface of the Builtin 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 + +| # | Builtin 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 + +| # | Builtin 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 Similarity + +So, how do the two relate? +Listed below is an analysis of every built-in interface. +Each is compared against what `go-cuckoo` offers, and if any changes seem necessary. + +Specifically, here we are checking for functionality. +Is there functionality that this offers which `go-cuckoo` does not? +This check will check 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 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 is: + +```go +m := New[K, V]() +for k, v := range startingEntries { + m.Put(k, v) +} +``` + +While it is idiomatic, it is far less ergonomic. + +
+ +
+var m map[K]V + +The analog is `var m Table[K, V]`. + +
+ +
+m[k] := v + +
+ +
+v := m[k] + +
+ +
+v, ok := m[k] + +
+ +
+for k, v := range m + +
+ +
+delete(m, k) + +
+ +
+clear(m) + +
+ +
+n := len(m) + +
+ +
+m2 := maps.Clone(m) + +
+ +
+maps.Copy(dst, src) + +
+ +
+ok := maps.Equal(m1, m2) + +
+ +
+ok := maps.EqualFunc(m1, m2, fn) + +
+ +
+maps.DeleteFunc(m, fn) + +
+ +
+it2 := maps.All(m) + +
+ +
+it := maps.Keys(m) + +
+ +
+it := maps.Values(m) + +
+ +
+m := maps.Collect(seq) + +
+ +
+maps.Insert(m, seq) + +
+ +## Target State