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GroupBy

func GroupBy[K comparable, V any, G comparable](mapInstance map[K]V, grouper func(key K, value V) G) map[G]map[K]V

GroupBy groups map entries by a grouping key generated from each entry. Returns a map where keys are group identifiers and values are maps of entries belonging to that group.

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package main

import (
    "fmt"
    "strings"

    "github.com/Goldziher/go-utils/maputils"
)

func main() {
    scores := map[string]int{
        "Alice":   95,
        "Bob":     67,
        "Charlie": 88,
        "David":   72,
        "Eve":     91,
    }

    // Group by grade (A: 90+, B: 80-89, C: 70-79, etc.)
    byGrade := maputils.GroupBy(scores, func(name string, score int) string {
        switch {
        case score >= 90:
            return "A"
        case score >= 80:
            return "B"
        case score >= 70:
            return "C"
        default:
            return "F"
        }
    })

    fmt.Printf("%v\n", byGrade)
    // map[A:map[Alice:95 Eve:91] B:map[Charlie:88] C:map[Bob:67 David:72]]
}