Is there any way to transform a variable (let) to constant (const)?

Question

Does Rust have a method to transform a variable declared as let to a constant?

I would like to initialize an array with the size defined by the variable (tam), as I couldn't, I initialized with the size 90000. Is there any way to do this initialization with the variable (tam)?

    //the variable tam receives an i32 that represents the size of the input and I would 
    //like to initialize an array with this size -> //let mut cities: [[i32; 2]; tam] = [[0; 2]; tam]; 

    let args: Vec<String> = env::args().collect();
    let filename = &args[1];
    let tam: &i32 = &args[2].parse::<i32>().unwrap();
    //let mut cities: [[i32; 2]; tam] = [[0; 2]; tam]; 
    let mut cities: [[i32; 2]; 90000] = [[0; 2]; 90000]; 

Answer 1

No it is not possible to convert a variable to a const in Rust. Rust consts are more like a C #define than a variable, in that is in inlined, "copy-pasted", in all locations that uses it during compilation.

I would suggest making cities a Vec since that is something that you can dynamically size during runtime.