What are Anonymous Structs and Empty Structs in Go, and How Are They Used for Signaling?

Anonymous Struct and Empty Struct

In Go, an anonymous struct is a struct that does not have a name. It is typically used to create temporary or short-lived data structures. An empty struct has no fields and occupies zero bytes of memory.

[1st Question]

The following code uses an anonymous struct to signal that a warrior has finished fighting:

done := make(chan struct{})

The struct{} type represents an empty struct. It is used here because we don't need to store any data in the struct. We only want to use it to signal that a warrior has finished fighting.

The following line sends the empty struct to the done channel:

done <- struct{}{}

The extra brackets are required because the < and > operators have lower precedence than the <- operator. Without the brackets, the code would be interpreted as done <- (struct{}) {}, which would send a pointer to an empty struct instead of an empty struct itself.

[2nd Question]

The following line waits for all the warriors to finish fighting:

for _ = range langs { <-done }

This line uses a range expression to receive from the done channel. The _ character is used as a placeholder variable to indicate that we don't care about the value received. This is because the empty struct sent by the warriors does not contain any data.

The range expression is necessary because it allows the program to wait for all the warriors to finish fighting before continuing. Without it, the program would only wait for the first warrior to finish fighting before continuing.

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