fix!: removed all 'mixed pointer'-edness

## Description

Currently, the signature for `Table.Get` is `func (K) (V, error)`. This is not very Go-idiomatic, which prefers to return a boolean instead of an error. For instance, a built-in Go map is used like so:

```go
if value, ok := users[id]; !ok {
  // ...
}
```

Updating our table to look like that is best practice. In that same vein, to support direct lookup (i.e. `v := users[id]`), this PR also adds `Table.Find`.

## Changes

- BREAKING CHANGE: Update contract of `Table.Get` to `func (K) (V, bool)`. Returns 'false' is the item cannot be found, and 'true' if it is found.
- Add `Table.Find`.
- Updated tests and documentation to match the change.

### Design Decisions

- Chose to make this decision because throwing an error implies that there is something 'wrong' with the table. There is nothing wrong with the table; it is just that the item does not exist.

## Checklist

- [x] Tests pass
- [x] Docs updated

Reviewed-on: #20
Co-authored-by: M.V. Hutz <git@maximhutz.me>
Co-committed-by: M.V. Hutz <git@maximhutz.me>

.claude/settings.json

@@ -1,7 +0,0 @@
-{
-  "permissions": {
-    "allow": [
-      "Bash(curl -s -w \"\\\\n---HTTP_STATUS:%{http_code}---\" https://raw.githubusercontent.com/kubernetes/kubernetes/master/.markdownlint.yaml)"
-    ]
-  }
-}

.gitea/ISSUE_TEMPLATE/BUG_REPORT.yml

@@ -0,0 +1,26 @@
+# yaml-language-server: $schema=https://www.schemastore.org/gitea-issue-forms.json
+name: 🐛 Bug Report
+about: Report a bug in this project
+title: "[BUG]: "
+body:
+  - type: textarea
+    id: context
+    attributes:
+      label: Context
+      placeholder: What circumstances led to the bug?
+    validations:
+      required: true
+  - type: textarea
+    id: expected-behavior
+    attributes:
+      label: Expected Behavior
+      placeholder: What did you expect would happen?
+    validations:
+      required: true
+  - type: textarea
+    id: actual-behavior
+    attributes:
+      label: Actual Behavior
+      placeholder: What happened, and why was it unexpected?
+    validations:
+      required: true

.gitea/ISSUE_TEMPLATE/FEATURE_REQUEST.yml

@@ -0,0 +1,37 @@
+# 'Feature Request Template' By @cheehwatang
+# https://github.com/cheehwatang/.github/blob/master/.github/ISSUE_TEMPLATE/feature_request.yml
+#
+# yaml-language-server: $schema=https://www.schemastore.org/gitea-issue-forms.json
+name: ✨ Feature Request
+about: Suggest an idea for this project
+title: "[FEATURE]: "
+body:
+  - type: dropdown
+    attributes:
+      multiple: false
+      label: Feature Type
+      options:
+        - "✨ New Feature"
+        - "📝 Documentation"
+        - "🎨 Style and UI"
+        - "🔨 Code Refactor"
+        - "⚡ Performance Improvements"
+        - "✅ New Test"
+    validations:
+      required: true
+  - type: textarea
+    id: description
+    attributes:
+      label: Description
+      placeholder: |
+        Give us a brief description of the feature or enhancement you would
+        like!
+    validations:
+      required: true
+  - type: textarea
+    id: additional-information
+    attributes:
+      label: Additional Information
+      placeholder: |
+        Give us some additional information on the feature request like proposed
+        solutions, links, screenshots, etc.

.gitea/ISSUE_TEMPLATE/config.yml

@@ -0,0 +1,2 @@
+# yaml-language-server: $schema=https://www.schemastore.org/gitea-issue-config.json
+blank_issues_enabled: false

.gitea/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,17 @@
+---
+name: "New Pull Request"
+about: "Standard PR template"
+title: ""
+ref: "main"
+---
+
+## Description
+
+## Changes
+
+### Design Decisions
+
+## Checklist
+
+- [ ] Tests pass
+- [ ] Docs updated

.gitea/workflows/ci.yml

@@ -6,6 +6,19 @@ on:
   pull_request:
 
 jobs:
+  check-pr-title:
+    name: Check PR Title
+    runs-on: ubuntu-latest
+    if: github.event_name == 'pull_request'
+    env:
+      TITLE: ${{ gitea.event.pull_request.title }}
+    steps:
+      - run: |
+          if ! echo "$TITLE" | grep -qE '^(WIP: )?(feat|fix|docs|chore|ci|test|refactor|perf|build|style|revert)(\(.+\))?(!)?: .+'; then
+            echo "::error::Pull Request title must follow conventional commits"
+            exit 1
+          fi
+
   lint-go:
     name: Go Lint
     runs-on: ubuntu-latest

.gitignore

@@ -24,4 +24,3 @@ go.work.sum
 
 # env file
 .env
-

.golangci.yml

@@ -114,6 +114,9 @@ linters:
     # Reports uses of functions with replacement inside the testing package.
     - usetesting
 
+    # Reports mixed receiver types in structs/interfaces.
+    - recvcheck
+
   settings:
     revive:
       rules:

bucket.go

@@ -19,11 +19,11 @@ type bucket[K, V any] struct {
 
 // location determines where in the bucket a certain key would be placed. If the
 // capacity is 0, this will panic.
-func (b bucket[K, V]) location(key K) uint64 {
+func (b *bucket[K, V]) location(key K) uint64 {
 	return b.hash(key) % b.capacity
 }
 
-func (b bucket[K, V]) get(key K) (value V, found bool) {
+func (b *bucket[K, V]) get(key K) (value V, found bool) {
 	if b.capacity == 0 {
 		return
 	}
@@ -54,7 +54,7 @@ func (b *bucket[K, V]) resize(capacity uint64) {
 	b.size = 0
 }
 
-func (b bucket[K, V]) update(key K, value V) (updated bool) {
+func (b *bucket[K, V]) update(key K, value V) (updated bool) {
 	if b.capacity == 0 {
 		return
 	}

cuckoo_fuzz_test.go

@@ -1,7 +1,9 @@
 package cuckoo_test
 
 import (
+	"fmt"
 	"maps"
+	"os"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
@@ -25,8 +27,9 @@ type fuzzStep struct {
 }
 
 type fuzzScenario struct {
-	seedA, seedB uint32
-	steps        []fuzzStep
+	seedA, seedB           uint32
+	capacity, growthFactor uint8
+	steps                  []fuzzStep
 }
 
 func FuzzInsertLookup(f *testing.F) {
@@ -40,14 +43,25 @@ func FuzzInsertLookup(f *testing.F) {
 			return
 		}
 
-		if scenario.seedA == scenario.seedB {
-			return
+		seedA, seedB := scenario.seedA, scenario.seedB
+		growthFactor := max(2, int(scenario.growthFactor))
+		capacity := int(scenario.capacity)
+
+		// If they are the same number, the hashes will clash, always causing an
+		// error.
+		if seedA == seedB {
+			t.Skip()
 		}
 
+		fmt.Fprintf(os.Stderr, "seedA=%d seedB=%d capacity=%d growthFactor=%d\n",
+			seedA, seedB, capacity, growthFactor)
+
 		actual := cuckoo.NewCustomTable[uint32, uint32](
-			offsetHash(scenario.seedA),
-			offsetHash(scenario.seedB),
+			offsetHash(seedA),
+			offsetHash(seedB),
 			func(a, b uint32) bool { return a == b },
+			cuckoo.Capacity(capacity),
+			cuckoo.GrowthFactor(growthFactor),
 		)
 
 		expected := map[uint32]uint32{}
@@ -59,16 +73,16 @@ func FuzzInsertLookup(f *testing.F) {
 
 				delete(expected, step.key)
 
-				_, err = actual.Get(step.key)
-				assert.Error(err)
+				_, ok := actual.Get(step.key)
+				assert.False(ok)
 			} else {
 				err := actual.Put(step.key, step.value)
 				assert.NoError(err)
 
 				expected[step.key] = step.value
 
-				found, err := actual.Get(step.key)
-				assert.NoError(err)
+				found, ok := actual.Get(step.key)
+				assert.True(ok)
 				assert.Equal(step.value, found)
 			}
 

cuckoo_test.go

@@ -108,12 +108,12 @@ func TestGetMany(t *testing.T) {
 	}
 
 	for i := range 2_000 {
-		value, err := table.Get(i)
+		value, ok := table.Get(i)
 		if i < 1_000 {
-			assert.NoError(err)
+			assert.True(ok)
 			assert.Equal(value, true)
 		} else {
-			assert.Error(err)
+			assert.False(ok)
 		}
 	}
 }

doc_example_test.go

@@ -14,19 +14,19 @@ func Example_basic() {
 		fmt.Println("Put error:", err)
 	}
 
-	if item, err := table.Get(1); err != nil {
-		fmt.Println("Error:", err)
+	if item, ok := table.Get(1); !ok {
+		fmt.Println("Not Found 1!")
 	} else {
 		fmt.Println("Found 1:", item)
 	}
 
-	if item, err := table.Get(0); err != nil {
-		fmt.Println("Error:", err)
+	if item, ok := table.Get(0); !ok {
+		fmt.Println("Not Found 0!")
 	} else {
 		fmt.Println("Found 0:", item)
 	}
 
 	// Output:
 	// Found 1: Hello, World!
-	// Error: key '0' not found
+	// Not Found 0!
 }

settings.go

@@ -1,5 +1,7 @@
 package cuckoo
 
+import "fmt"
+
 // DefaultCapacity is the initial capacity of a [Table]. It is inspired from
 // Java's [HashMap] implementation, which also uses 16.
 //
@@ -10,11 +12,12 @@ const DefaultCapacity uint64 = 16
 // hash table implementations use 2.
 const DefaultGrowthFactor uint64 = 2
 
-// DefaultMinimumLoad is the default lowest acceptable occupancy of a [Table].
-// The value of 5% is taken from [libcuckoo].
+// defaultMinimumLoad is the default lowest acceptable occupancy of a [Table].
+// The higher the minimum load, the more likely that a [Table.Put] will not
+// succeed. The value of 5% is taken from [libcuckoo].
 //
 // [libcuckoo]: https://github.com/efficient/libcuckoo/blob/656714705a055df2b7a605eb3c71586d9da1e119/libcuckoo/cuckoohash_config.hh#L21
-const DefaultMinimumLoad float64 = 0.05
+const defaultMinimumLoad float64 = 0.05
 
 type settings struct {
 	growthFactor  uint64
@@ -27,19 +30,21 @@ type settings struct {
 type Option func(*settings)
 
 // Capacity modifies the starting capacity of each bucket of the [Table]. The
-// value must be greater than 0.
+// value must be non-negative.
 func Capacity(value int) Option {
-	return func(s *settings) { s.bucketSize = uint64(value) }
-}
+	if value < 0 {
+		panic(fmt.Sprintf("go-cuckoo: Capacity must be non-negative, got %d", value))
+	}
 
-// MinimumLoad modifies the [DefaultMinimumLoad] of the [Table]. The value must
-// be between 0.00 and 1.00.
-func MinimumLoad(value float64) Option {
-	return func(s *settings) { s.minLoadFactor = value }
+	return func(s *settings) { s.bucketSize = uint64(value) }
 }
 
 // GrowthFactor controls how much the capacity of the [Table] multiplies when
 // it must resize. The value must be greater than 1.
 func GrowthFactor(value int) Option {
+	if value < 2 {
+		panic(fmt.Sprintf("go-cuckoo: GrowthFactor must be greater than 1, got %d", value))
+	}
+
 	return func(s *settings) { s.growthFactor = uint64(value) }
 }

table.go

@@ -1,12 +1,21 @@
 package cuckoo
 
 import (
+	"errors"
 	"fmt"
 	"iter"
 	"math/bits"
 	"strings"
 )
 
+// ErrBadHash occurs when the hashes given to a [Table] cause too many key
+// collisions. Try rebuilding the table using:
+//
+//  1. Different hash seeds. Equal seeds produce equal hash functions, which
+//     always cycle.
+//  2. A different [Hash] algorithm.
+var ErrBadHash = errors.New("bad hash")
+
 // A Table is hash table that uses cuckoo hashing to resolve collision. Create
 // one with [NewTable]. Or if you want more granularity, use [NewTableBy] or
 // [NewCustomTable].
@@ -18,12 +27,12 @@ type Table[K, V any] struct {
 
 // TotalCapacity returns the number of slots allocated for the [Table]. To get the
 // number of slots filled, look at [Table.Size].
-func (t Table[K, V]) TotalCapacity() uint64 {
+func (t *Table[K, V]) TotalCapacity() uint64 {
 	return t.bucketA.capacity + t.bucketB.capacity
 }
 
 // Size returns how many slots are filled in the [Table].
-func (t Table[K, V]) Size() int {
+func (t *Table[K, V]) Size() int {
 	return int(t.bucketA.size + t.bucketB.size)
 }
 
@@ -31,11 +40,11 @@ func log2(n uint64) (m int) {
 	return max(0, bits.Len64(n)-1)
 }
 
-func (t Table[K, V]) maxEvictions() int {
+func (t *Table[K, V]) maxEvictions() int {
 	return 3 * log2(t.TotalCapacity())
 }
 
-func (t Table[K, V]) load() float64 {
+func (t *Table[K, V]) load() float64 {
 	// When there are no slots in the table, we still treat the load as 100%.
 	// Every slot in the table is full.
 	if t.TotalCapacity() == 0 {
@@ -86,24 +95,31 @@ func (t *Table[K, V]) shrink() error {
 	return t.resize(t.bucketA.capacity / t.growthFactor)
 }
 
-// Get fetches the value for a key in the [Table]. Returns an error if no value
-// is found.
-func (t Table[K, V]) Get(key K) (value V, err error) {
+// Get fetches the value for a key in the [Table]. Matches the comma-ok pattern
+// of a builtin map; see [Table.Find] for plain indexing.
+func (t *Table[K, V]) Get(key K) (value V, ok bool) {
 	if item, ok := t.bucketA.get(key); ok {
-		return item, nil
+		return item, true
 	}
 
 	if item, ok := t.bucketB.get(key); ok {
-		return item, nil
+		return item, true
 	}
 
-	return value, fmt.Errorf("key '%v' not found", key)
+	return
+}
+
+// Find fetches the value of a key. Matches direct indexing of a builtin map;
+// see [Table.Get] for a comma-ok pattern.
+func (t *Table[K, V]) Find(key K) (value V) {
+	value, _ = t.Get(key)
+	return
 }
 
 // Has returns true if a key has a value in the table.
-func (t Table[K, V]) Has(key K) (exists bool) {
-	_, err := t.Get(key)
-	return err == nil
+func (t *Table[K, V]) Has(key K) (exists bool) {
+	_, exists = t.Get(key)
+	return
 }
 
 // Put sets the value for a key. Returns error if its value cannot be set.
@@ -128,7 +144,7 @@ func (t *Table[K, V]) Put(key K, value V) (err error) {
 	}
 
 	if t.load() < t.minLoadFactor {
-		return fmt.Errorf("bad hash: resize on load %d/%d = %f", t.Size(), t.TotalCapacity(), t.load())
+		return fmt.Errorf("hash functions produced a cycle at load %d/%d: %w", t.Size(), t.TotalCapacity(), ErrBadHash)
 	}
 
 	if err := t.grow(); err != nil {
@@ -152,7 +168,7 @@ func (t *Table[K, V]) Drop(key K) (err error) {
 }
 
 // Entries returns an unordered sequence of all key-value pairs in the table.
-func (t Table[K, V]) Entries() iter.Seq2[K, V] {
+func (t *Table[K, V]) Entries() iter.Seq2[K, V] {
 	return func(yield func(K, V) bool) {
 		for _, slot := range t.bucketA.slots {
 			if slot.occupied {
@@ -174,7 +190,7 @@ func (t Table[K, V]) Entries() iter.Seq2[K, V] {
 
 // String returns the entries of the table as a string in the format:
 // "table[k1:v1 h2:v2 ...]".
-func (t Table[K, V]) String() string {
+func (t *Table[K, V]) String() string {
 	var sb strings.Builder
 	sb.WriteString("table[")
 
@@ -198,7 +214,7 @@ func NewCustomTable[K, V any](hashA, hashB Hash[K], compare EqualFunc[K], option
 	settings := &settings{
 		growthFactor:  DefaultGrowthFactor,
 		bucketSize:    DefaultCapacity,
-		minLoadFactor: DefaultMinimumLoad,
+		minLoadFactor: defaultMinimumLoad,
 	}
 
 	for _, option := range options {