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

问题

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 .Pop() by removing the first element in elements.

In many other languages, "popping" the first element of a list is a one-liner, which leads me to believe my implementation below is sloppy and verbose. Is there a better way?

type Queue struct {
    elements []interface{}
}

func (queue *Queue) Push(element interface{}) {
    queue.elements = append(queue.elements, element)
}

func (queue *Queue) Pop() interface{} {
    element := queue.elements[0]
    if len(queue.elements) > 1 {
        queue.elements = queue.elements[1:]
    } else {
        queue.elements = make([]interface{}, 0)
    }
    return element
}

Please note that I wish for the Queue to panic if len(queue.elements) == 0. It's not an oversight that I don't check the bounds.

回答1:

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

回答2:

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())

}

来源：https://stackoverflow.com/questions/23531891/how-do-i-succinctly-remove-the-first-element-from-a-slice-in-go

标签

queue