[]const T

[iperov]

How to return immutable view of a dynamic array?

for example as a data cache.
https://play.vlang.io/p/908e1b8d7d

struct Host {
mut:
	cached []int	
}

fn (mut self Host) numbers() []int {
	if self.cached.len == 0 {
		self.cached = [0,0,0]
	}
	return self.cached // Can be mutated by caller
	//return self.cached.clone() // Expensive
}

fn main() 
{  
	mut h := Host{}
	mut numbers := h.numbers()
	numbers[0] = 1
	
	println(h.cached) // [1,0,0]
}

[gechandesu]

This looks like a bug for me. Host.cached is mutated even if Host is declared in separate module:

main.v
host/
├── host.v
└── v.mod

// host/host.v
module host

pub struct Host {
mut:
        cached []int
}

pub fn (mut self Host) numbers() []int {
        if self.cached.len == 0 {
                self.cached = [0, 0, 0]
        }
        return self.cached // Can be mutated by caller
        // return self.cached.clone() // Expensive
}

// main.v
import host

fn main() {
        mut h := host.Host{}
        mut numbers := h.numbers()
        numbers[0] = 1

        println(h)
}
// host.Host{
//     cached: [1, 0, 0] // mutated!
// }