go-maputil

Generic map utilities for Go. Filter, transform, merge, group, and more

Installation

go get github.com/philiprehberger/go-maputil

Usage

Filter & Transform

import "github.com/philiprehberger/go-maputil"

scores := map[string]int{"alice": 90, "bob": 45, "charlie": 72}

// Keep entries where value > 50
high := maputil.Filter(scores, func(_ string, v int) bool {
    return v > 50
})
// {"alice": 90, "charlie": 72}

// Double all values
doubled := maputil.Map(scores, func(_ string, v int) int {
    return v * 2
})
// {"alice": 180, "bob": 90, "charlie": 144}

Merge

defaults := map[string]int{"timeout": 30, "retries": 3}
overrides := map[string]int{"timeout": 60}

config := maputil.Merge(defaults, overrides)
// {"timeout": 60, "retries": 3}

// Merge with conflict resolution
summed := maputil.MergeWith(func(_ string, a, b int) int {
    return a + b
}, defaults, overrides)
// {"timeout": 90, "retries": 3}

Pick & Omit

m := map[string]int{"a": 1, "b": 2, "c": 3, "d": 4}

picked := maputil.Pick(m, "a", "c")
// {"a": 1, "c": 3}

omitted := maputil.Omit(m, "b", "d")
// {"a": 1, "c": 3}

Any & All

scores := map[string]int{"alice": 90, "bob": 45, "charlie": 72}

hasHigh := maputil.Any(scores, func(_ string, v int) bool {
    return v >= 90
})
// true

allPassing := maputil.All(scores, func(_ string, v int) bool {
    return v >= 50
})
// false (bob has 45)

GetOrDefault

config := map[string]int{"timeout": 30, "retries": 3}

timeout := maputil.GetOrDefault(config, "timeout", 60)
// 30 (key exists)

maxConns := maputil.GetOrDefault(config, "max_conns", 10)
// 10 (key missing, returns fallback)

Find

scores := map[string]int{"alice": 90, "bob": 45, "charlie": 72}

name, score, ok := maputil.Find(scores, func(_ string, v int) bool {
    return v >= 90
})
// name="alice", score=90, ok=true

Partition

scores := map[string]int{"alice": 90, "bob": 45, "charlie": 72}

passing, failing := maputil.Partition(scores, func(_ string, v int) bool {
    return v >= 50
})
// passing: {"alice": 90, "charlie": 72}
// failing: {"bob": 45}

Diff

v1 := map[string]int{"a": 1, "b": 2, "c": 3}
v2 := map[string]int{"b": 2, "c": 30, "d": 4}

added, removed, changed := maputil.Diff(v1, v2)
// added:   {"d": 4}
// removed: {"a": 1}
// changed: {"c": 30}

GroupBy

type User struct {
    Name       string
    Department string
}

users := []User{
    {"Alice", "Engineering"},
    {"Bob", "Marketing"},
    {"Charlie", "Engineering"},
}

grouped := maputil.GroupBy(users, func(u User) string {
    return u.Department
})
// {"Engineering": [{Alice, Engineering}, {Charlie, Engineering}], "Marketing": [{Bob, Marketing}]}

counts := maputil.CountBy(users, func(u User) string {
    return u.Department
})
// {"Engineering": 2, "Marketing": 1}

API

Function	Description
Filter	Return map with entries matching predicate
Map	Transform values
MapKeys	Transform keys
Merge	Merge maps, last wins
MergeWith	Merge with conflict resolution
Pick	Select only given keys
Omit	Exclude given keys
Invert	Swap keys and values
Keys	Extract keys (unordered)
SortedKeys	Extract keys sorted
Values	Extract values
Contains	Check if key exists
Size	Return map size
Any	True if any entry matches predicate
All	True if all entries match predicate
GetOrDefault	Get value or return fallback
Find	First entry matching predicate
Partition	Split map by predicate
Diff	Compare two maps (added, removed, changed)
GroupBy	Group slice elements by key
CountBy	Count elements per group
UniqueBy	Last element per group

Development

go test ./...
go vet ./...

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License

MIT