On Wed, Jul 10, 2024 at 4:17 PM Justin Scheiber <jschei...@gmail.com> wrote:
>
> I'm trying to establish a mental model for what the compiler does with range
> functions in Go 1.23. It looks like the compiler creates a function based on
> the for loop body, and calls it by looping over the values passed in.
>
> Meaning this code:
> func simpleIter(yield func(v int) bool) {
> if !yield(1) {
> return
> }
> if !yield(2) {
> return
> }
> }
>
> for x := range simpleIter {
> fmt.Println(x)
> }
>
> compiles into this code:
>
> {
> yield := func(v int) bool {
> fmt.Println(v) // loop body from the code above
> }
> for v := 1; v <= 2; v++ {
> if !yield(1) {
> goto end_loop
> }
> }
> end_loop:
> }
>
> Is that correct?
Sort of. I 'm not sure where the "for v := 1; v <= 2; v++" comes
from. Your yield function is more or less correct, but then the
compiler just calls "simpleIter(yield)".
It's a bit more complicated because the loop can contain break
statements, return statements, or panics. Those cause the generated
yield function to return false.
Ian
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