go-data-structureslisted

# Go Data Structures > **Source**: Effective Go This skill covers Go's built-in data structures and allocation primitives. --- ## Allocation: new vs make Go has two allocation primitives: `new` and `make`. They do different things. ### new `new(T)` allocates zeroed storage for a new item of type `T` and returns `*T`: ```go p := new(SyncedBuffer) // type *SyncedBuffer, zeroed var v SyncedBuffer // type SyncedBuffer, zeroed ``` **Zero-value design**: Design data structures so the zero value is useful without further initialization. Examples: `bytes.Buffer`, `sync.Mutex`. ```go type SyncedBuffer struct { lock sync.Mutex buffer bytes.Buffer } // Ready to use immediately upon allocation ``` ### make `make(T, args)` creates slices, maps, and channels only. It returns an **initialized** (not zeroed) value of type `T` (not `*T`): ```go make([]int, 10, 100) // slice: length 10, capacity 100 make(map[string]int) // map: ready to use make(chan int) // channel: ready to use ``` ### The Difference ```go var p *[]int = new([]int) // *p == nil; rarely useful var v []int = make([]int, 100) // v is a usable slice of 100 ints // Idiomatic: v := make([]int, 100) ``` **Rule**: `make` applies only to maps, slices, and channels and does not return a pointer. --- ## Composite Literals Create and initialize structs, arrays, slices, and maps in one expression: ```go // Struct with positional fields f := File{fd, name, nil, 0} // Struct with nam