在Go中循环循环

Question

Correct me if I'm wrong, there are only 3 types of loops in Go.

Type1 (The most basic type, with a single condition):

for i <= 3 {...}

Type2 (Classical for-loop)

for j := 7; j <= 9; j++ {...}

Type3 (infinite loop rely on break)

for {...break}

Then I come across this for loop that sums the value from array

nums := []int{2, 3, 4}
sum := 0
for _, num := range nums {
    sum += num
}
fmt.Println("sum:", sum)//"sum: 9"

Is the above for-loop to be considered Type1 where it automatically applies <= and range of nums as max value? Can I in any way change the value? maybe I need two extra loops? Can we apply something like range + 2?

Answer 1

From Effective Go:

The Go for loop is similar to—but not the same as—C's. It unifies for and while and there is no do-while. There are three forms, only one of which has semicolons.

// Like a C for
for init; condition; post { }

// Like a C while
for condition { }

// Like a C for(;;)
for { }

It continues:

If you're looping over an array, slice, string, or map, or reading from a channel, a range clause can manage the loop.

for key, value := range oldMap {
        newMap[key] = value
}

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From this I think of range loops as a for condition { } loop, where the condition (such as it is) is that the variables being designated as the values of the array/slice/string/map/chan are not nil, though in practice even explicitly nil values work

for _, v := range []interface{}{nil, nil, nil, nil} {
    // will still iterate four times
}

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In reality it might be more useful to think of Go's for loop as a contextual combination of a C-style for init; condition; post loop, a classical while loop, and a more modern foreach loop.