How do I (succinctly) remove the first element from a slice in Go?

Question

I\'ve built a simple queue in Go. It uses an internal slice to keep track of its elements. Elements are pushed onto the queue by appending to the slice. I\'d like to implement <

Answer 1

If you want a ring buffer or FIFO structure then using a slice as in @Everton's answer will cause garbage collection problems as the underlying array may grow indefinitely.

The easiest way to do this in go, provided you don't mind having a limited size, is to use a channel which is also safe for concurrent access. This is such a common idiom in go that you wouldn't usually bother wrapping it in a type like the below.

Eg (Playground)

package main

import "fmt"

type Queue struct {
    elements chan interface{}
}

func NewQueue(size int) *Queue {
    return &Queue{
        elements: make(chan interface{}, size),
    }
}

func (queue *Queue) Push(element interface{}) {
    select {
    case queue.elements <- element:
    default:
        panic("Queue full")
    }
}

func (queue *Queue) Pop() interface{} {
    select {
    case e := <-queue.elements:
        return e
    default:
        panic("Queue empty")
    }
    return nil
}

func main() {
    q := NewQueue(128)

    q.Push(1)
    q.Push(2)
    q.Push(3)
    fmt.Printf("Pop %d\n", q.Pop())
    fmt.Printf("Pop %d\n", q.Pop())
    fmt.Printf("Pop %d\n", q.Pop())
    fmt.Printf("Pop %d\n", q.Pop())

}

Answer 2

Did you try these?

Pop from queue

x, a = a[0], a[1:]

Pop from stack

x, a = a[len(a)-1], a[:len(a)-1]

Push

a = append(a, x)

From: https://code.google.com/p/go-wiki/wiki/SliceTricks