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Creating Python's `next()` alternative using Go Closures
If you don't know what next() in python means, the below code illustrates it.
MCU_Movies = iter(["Iron Man", "Thor", "Captain America: The first Avenger"])
x = next(MCU_Movies)
print(x, end="\n")
x = next(MCU_Movies)
print(x, end="\n")
x = next(MCU_Movies)
print(x)
So if you had guess this would print
Iron Man
Thor
Captain America: The first Avenger
The next() function is used to get the next item in an iterator.
Go doesn't have a next method (nor the concept of iterators actually) so we will try to achieve something similar using Closures.
  • A closure is implemented through a anonymous(function with no name) function, basically closure is an instance of function.
  • In Go functions are first class citizens, meaning we can do all sort of things with them, assign them to a variable, pass as an argument to another function.
Below is a naive implementation of how this could look in Go. Ping me if you have a better way to do this ;)
package main
​
import "fmt"
​
/*
nextIterator returns another function, which we define anonymously in the body of nextIterator.
The returned function closes over the variable index to form a closure.
*/
func nextIterator(array []int) func() int {
index := -1
​
return func() int{
index++
return array[index]
}
}
func main() {
​
// an integer array
var prices = []int{7, 1, 5}
​
// create an instance of the anonymous function. i.e, a closue
next := nextIterator(prices)
​
// call the closure
fmt.Println(next())
fmt.Println(next())
fmt.Println(next())
​
}
See this demo on Go Playground.
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