Go Generic Join

January 6, 2023

// NestedJoin like nested loop join func NestedJoin[J, K, R any]( left []J, right []K, match func(J, K) bool, mapper func(J, K) R, ) []R { var r = make([]R, 0, len(left)) for _, j := range left { for _, k := range right { if !match(j, k) { continue } r = append(r, mapper(j, k)) } } return r } // HashJoin like hash join func HashJoin[K comparable, LE, RE, R any]( left []LE, right []RE, lk func(item LE) K, rk func(item RE) K, mapper func(LE, RE) R, ) []R { var r = make([]R, 0, len(left)) rm := KeyBy(right, rk) for _, le := range left { k := lk(le) re := rm[k] r = append(r, mapper(le, re)) } return r } Code From