`Iter.Seq`

Generics allow us to reuse a single function for many different argument types. With the iter.Seq type we can use a for-range loop over elements of a generic argument.

By receiving an iter.Seq instance in a function, we can use a for-loop. The slices.Values method in the slices package is a convenient way to get an iter.Seq from a slice.

Example

The goal of the iter package is to support for-loops over varying types of collections. This program introduces a generic method, CountWithFor, that receives an iter.Seq of any type.

Part 1 The CountWithFor method uses a for-range loop over an iter.Seq. The V refers to the any type, which is any valid Go type.

Part 2 Next the CountWithFor method prints the total number of elements in the Seq using a for-range loop.

Part 3 To go from a slice to an iter.Seq of any type, we can use the slices.Values method from the slices module.

package main

import (
    "iter"
    "slices"
    "fmt"
)

// Part 1: add generic function that loops over an iter.Seq of any type.
func CountWithFor[V any](seq iter.Seq[V]) {
    count := 0
    // Part 2: use for-loop over iter.Seq.
    for _ = range seq {
        count += 1
    }
    fmt.Println(count)
}

func main() {
    // Part 3: get iter.Seq arguments from slices with Slice.Values, and use CountWithFor.
    seq1 := slices.Values([]string{"bird", "frog", "dog"})
    CountWithFor(seq1)

    seq2 := slices.Values([]int{10, 20, 30, 40})
    CountWithFor(seq2)

    seq3 := slices.Values([]bool{false, true})
    CountWithFor(seq3)
}3
4
2

The iter module, and its Seq type, provide a way to receive an iterable collection of any element. For a functioning program, we can use slices.Values along with iter.Seq.