C++20 Improved the For-Loop Syntax

Re:C++20 Improved the For-Loop Syntax by entrope on Tuesday July 14, 2026 @10:25PM (#48915523)

Go is similar:

  package main

  import "fmt"

  var vec = []string{"the", "quick", "brown", "fox", "jumped", "over", "the", "lazy", "dog"}

  func main() {
    for i, s := range vec {
      fmt.Printf("%d: %s\n", i, s)
    }
  }

Using `fmt.Println(i, ":", s)` inserts spaces on both sides of the colon, so the output is not quite right.

I find Go's `range` syntax easier to read than D's `(i, s; vec)` -- although generator functions that work with `range` have unaesthetic return types.

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Re:C++20 Improved the For-Loop Syntax by WalterBright on Tuesday July 14, 2026 @10:29PM (#48915550)

D has several usages for `foreach` depending on the number and type of its arguments. In this case, it sees that `vec` is an array, and so constructs a loop over the array. If `vec` was a range, the loop will be constructed as a loop over the array.

It's nice because it makes the syntax for arrays and ranges interchangeable, making for easy refactoring.

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Re:C++20 Improved the For-Loop Syntax by entrope on Wednesday July 15, 2026 @07:28AM (#48919209)

Go is similar: `for/range` has always worked on arrays, slices, maps, strings and channels, and they extended it to integers in version 1.22 and to user-defined generators in version 1.23. It generates one or two outputs depending on the type of the RHS, but one can assign the index value to _ to ignore it. Among standard types, only channels and integers generate one output; containers (including strings) give an index or key and a value.

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Re:C++20 Improved the For-Loop Syntax by xigoi on Wednesday July 15, 2026 @09:35AM (#48920637)

I find Go’s version worse in that it does not allow you to elide the index (which is not needed most of the time). You have to write `for _, s := range vec`, as `for s := range vec` makes s the index.

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Re:C++20 Improved the For-Loop Syntax by WalterBright on Wednesday July 15, 2026 @01:39PM (#48924429)

To clarify,

    foreach (s; vec)

works if you don't need the index. To be able to modify s in place:

    foreach (ref s; vec) s = "replacement";

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Re:C++20 Improved the For-Loop Syntax by xigoi on Wednesday July 15, 2026 @05:34PM (#48927345)

I was talking about Go. I know you don’t need the index in D.

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