How to use the cap function in Go

The cap() function in Golang takes an input and returns its capacity depending on the input type.

Parameters and return value

The following table describes the types of a single input v that the cap() function accepts. The return value is of type int.

v	Description
array	The `cap()` function returns the number of elements in the array.
pointer to the array	The `cap()` function returns the number of elements in the array.
slice	The `cap()` function returns the number of elements in the underlying array.
channel	The `cap()` function returns the channel buffer capacity in units of elements.

package main
import "fmt"
func main() {
// create an array of 6 elements
  var arr [6] int
  // call the cap function
  capArr := cap(arr)
  fmt.Println("The capacity of the array is:")
  fmt.Println(capArr)
// create a slice of length 0 and capactiy 10
	slice := make([]string, 0, 10)
	capSlice := cap(slice)
  fmt.Println("The capacity of the slice is:")
  fmt.Println(capSlice)
// create a channel of capacity 5
	channel := make(chan string, 5)
	capChannel := cap(channel)
  fmt.Println("The capacity of the channel is:")
  fmt.Println(capChannel)
// create a pointer to an array of 20 elements
	var pointer *[20]string
	capPointer := cap(pointer)
  fmt.Println("The capacity of the pointer is:")
  fmt.Println(capPointer)
}

How to use the cap function in Go

Prototype

Parameters and return value

Examples