revert: remove duplicate of analysis

docs/adr/000_template.md

@@ -0,0 +1,15 @@
+# Title
+
+**Status**: <!-- Proposed, accepted, rejected, etc... -->
+
+## Context
+
+<!-- What is the issue that we're seeing that is motivating this decision or change? -->
+
+## Decision
+
+<!-- What is the change that we're proposing and/or doing? -->
+
+## Consequences
+
+<!-- What becomes easier or more difficult to do because of this change? -->

docs/adr/001_design_principles.md

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+# Adopt Congruent and Familiar Design For `go-cuckoo`
+
+**Status**: Proposed
+
+## Context
+
+I built `go-cuckoo`'s API interface without design intent.
+Up until now, I paid more attention implementing the underlying functionality of the cuckoo hashing.
+With the fundamentals of the algorithm built, I should revisit the interface.
+
+The goal of this project was to create an implementation of cuckoo hashing, while adhering to Go's idioms, and being as usable as possible.
+While the implementation does work, it lacks direction.
+
+## Decision
+
+To resolve this, I'm enforcing two new principles onto the contract of `go-cuckoo`:
+
+- **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.
+
+These principles should _guide_ the public interface of `go-cuckoo`.
+Neither should be treated absolutely, though.
+The behavior of `go-cuckoo` is distinct from `map`.
+Do not equate them.
+
+## Consequences
+
+1. The repository should support both design principles.
+   - [ ] Update the `README.md` and `doc.go` to reflect these principles.
+   - [ ] Update the contributing guide and pull request template to require these principles are met.
+2. The repository should contain a living document, describing the interface differences between `go-cuckoo` and `map`.
+   I should prioritize limiting any incongruencies.
+   - [ ] Produce the first draft to uncover any current incongruencies.
+   - [ ] Link the document to the `README.md`.
+3. Analyze the familiarity of `go-cuckoo`'s current interface.
+   Unlike the analysis of congruency, this should be a one time document.
+   Familiarity is implicit to users, and does not need to be referenced.
+   But, any rationale should be documented in commit messages, or future ADRs.
+   - [ ] Produce the analysis document.
+   - [ ] Resolve any issues found.

wip/INTERFACE_ANALYSIS.md

@@ -0,0 +1,643 @@
+# 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.
+
+<details>
+<summary>Interfaces</summary>
+
+| #   | 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.                                                                            |
+
+</details>
+
+### Interface of `go-cuckoo`
+
+On the other hand, here is the current contract for `go-cuckoo`.
+
+<details>
+<summary>Interfaces</summary>
+
+| #   | `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.                                                             |
+
+</details>
+
+### 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.
+
+<details>
+<summary>✅ <code>m := make(map[K]V)</code></summary>
+
+The analog is `m := New()`.
+
+</details>
+
+<details>
+<summary>⚠️ <code>m := make(map[K]V, hint)</code></summary>
+
+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.
+
+</details>
+
+<details>
+<summary>❌ <code>m := map[K]V{...}</code></summary>
+
+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.
+
+</details>
+
+<details>
+<summary>✅ <code>var m map[K]V</code></summary>
+
+The analog is `var m Table[K, V]`.
+
+</details>
+
+<details>
+<summary>✅ <code>m[k] := v</code></summary>
+
+The analog is `err := m.Put(k, v)`.
+
+</details>
+
+<details>
+<summary>✅ <code>v := m[k]</code></summary>
+
+The analog is `v := m.Find(k)`.
+
+</details>
+
+<details>
+<summary>✅ <code>v, ok := m[k]</code></summary>
+
+The analog is `v, ok := m.Get(k)`.
+
+</details>
+
+<details>
+<summary>✅ <code>for k, v := range m</code></summary>
+
+The analog is `for k, v := range m.Entries()`.
+
+</details>
+
+<details>
+<summary>✅ <code>delete(m, k)</code></summary>
+
+The analog is `ok := m.Drop(k)`.
+
+</details>
+
+<details>
+<summary>❌ <code>clear(m)</code></summary>
+
+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)
+}
+```
+
+</details>
+
+<details>
+<summary>✅ <code>n := len(m)</code></summary>
+
+The analog is `n := m.Size()`.
+
+</details>
+
+<details>
+<summary>❌ <code>m2 := maps.Clone(m)</code></summary>
+
+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.
+
+</details>
+
+<details>
+<summary>❌ <code>maps.Copy(dst, src)</code></summary>
+
+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)
+}
+```
+
+</details>
+
+<details>
+<summary>❌ <code>ok := maps.Equal(m1, m2)</code></summary>
+
+There is no analog.
+
+Users have to manually check the key-value pairs to determine equality.
+
+</details>
+
+<details>
+<summary>❌ <code>ok := maps.EqualFunc(m1, m2, fn)</code></summary>
+
+There is no analog.
+
+Users have to manually check the key-value pairs to determine equality.
+
+</details>
+
+<details>
+<summary>❌ <code>maps.DeleteFunc(m, fn)</code></summary>
+
+There is no analog.
+
+Users have to manually delete keys.
+
+</details>
+
+<details>
+<summary>✅ <code>it2 := maps.All(m)</code></summary>
+
+The analog is `it2 := m.Entries()`.
+
+</details>
+
+<details>
+<summary>⚠️ <code>it := maps.Keys(m)</code></summary>
+
+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() {
+  // ...
+}
+```
+
+</details>
+
+<details>
+<summary>⚠️ <code>it := maps.Values(m)</code></summary>
+
+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() {
+  // ...
+}
+```
+
+</details>
+
+<details>
+<summary>❌ <code>m := maps.Collect(seq)</code></summary>
+
+There is no analog.
+
+</details>
+
+<details>
+<summary>❌ <code>maps.Insert(m, seq)</code></summary>
+
+There is no analog.
+
+</details>
+
+### 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).
+
+<details>
+<summary>✅ <code>m := New(opts...)</code></summary>
+
+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
+
+</details>
+
+<details>
+<summary><code>m := NewBy(keyFunc, opts...)</code></summary>
+
+- Use `NewKeyed()`.
+
+</details>
+
+<details>
+<summary><code>m := NewCustom(hashA, hashB, equalFunc, opts...)</code></summary>
+
+- Use `NewHashed()`.
+
+</details>
+
+<details>
+<summary>❌ <code>seq := m.Entries()</code></summary>
+
+- Call it `All()`.
+
+</details>
+
+<details>
+<summary><code>v := m.Find(k)</code></summary>
+
+- Call it `m.Lookup()`. The name `m.Find` implies a search algorithm.
+
+</details>
+
+<details>
+<summary><code>v, ok := m.Get(k)</code></summary>
+
+</details>
+
+<details>
+<summary><code>ok := m.Has(k)</code></summary>
+
+</details>
+
+<details>
+<summary>❌ <code>err := m.Put(k, v)</code></summary>
+
+- Call it `Set()`.
+- No built-in library consensus, but 3rd party packages prefer `Set()`.
+
+</details>
+
+<details>
+<summary>❌ <code>n := m.Size()</code></summary>
+
+- Call it `Len()`.
+- Size is a Java idiom.
+
+</details>
+
+<details>
+<summary>✅ <code>str := m.String()</code></summary>
+
+</details>
+
+<details>
+<summary>❌ <code>cap := m.TotalCapacity()</code></summary>
+
+- Remove. This is an implementation detail.
+
+</details>
+
+<details>
+<summary>❌ <code>ok := m.Drop(k)</code></summary>
+
+- Call it `Delete()`.
+
+</details>
+
+## Target State
+
+### Solving Congruency
+
+We should make the following changes to accomodate for congruency:
+
+<details>
+<summary><code>ok := maps.EqualFunc(m1, m2, fn)</code></summary>
+
+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`.
+
+</details>
+
+<details>
+<summary><code>ok := maps.Equal(m1, m2)</code></summary>
+
+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.
+
+</details>
+
+<details>
+<summary><code>maps.Insert(m, seq)</code></summary>
+
+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`.
+
+</details>
+
+<details>
+<summary><code>maps.Copy(dst, src)</code></summary>
+
+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.
+
+</details>
+
+<details>
+<summary><code>maps.DeleteFunc(m, fn)</code></summary>
+
+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()`.
+
+</details>
+
+<details>
+<summary><code>m := maps.Collect(seq)</code></summary>
+
+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)
+```
+
+</details>
+
+<details>
+<summary><code>m := map[K]V{...}</code></summary>
+
+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.
+
+</details>
+
+<details>
+<summary><code>m := make(map[K]V, hint)</code></summary>
+
+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.
+
+</details>
+
+<details>
+<summary><code>clear(m)</code></summary>
+
+We should implement a new receiver:
+
+```go
+func (t *Table[K, V]) Clear()
+```
+
+It will remove all entries from the table.
+
+</details>
+
+<details>
+<summary><code>m2 := maps.Clone(m)</code></summary>
+
+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.
+
+</details>
+
+<details>
+<summary><code>it := maps.Keys(m)</code></summary>
+
+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.
+
+</details>
+
+<details>
+<summary><code>it := maps.Values(m)</code></summary>
+
+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()`.
+
+</details>