CODEWITHSUNDEEP
arraysvectorrust
Swantewit
Swantewit

Reputation: 1076

Pushing array values to a vector in Rust

The Rust Programming Language has a task to print The Twelve Days of Christmas taking advantage of its repetitiveness.

My idea was to gather all the presents in an array and push them to the vector which would be printed from iteration to iteration.

It seems that it's either impossible, not easy, or I don't get something.

The code:

fn main() {
    let presents = [
        "A song and a Christmas tree",
        "Two candy canes",
        "Three boughs of holly",
    ];

    let mut current_presents = Vec::new();

    for day in presents {
        current_presents.push(presents[day]);
        println!(
            "On the {} day of Christmas my good friends brought to me",
            day + 1
        );
        println!("{current_presents} /n");
    }
}

error[E0277]: the type `[&str]` cannot be indexed by `&str`
  --> src/main.rs:11:31
   |
11 |         current_presents.push(presents[day]);
   |                               ^^^^^^^^^^^^^ slice indices are of type `usize` or ranges of `usize`
   |
   = help: the trait `SliceIndex<[&str]>` is not implemented for `&str`
   = note: required because of the requirements on the impl of `Index<&str>` for `[&str]`

error[E0369]: cannot add `{integer}` to `&str`
  --> src/main.rs:14:17
   |
14 |             day + 1
   |             --- ^ - {integer}
   |             |
   |             &str

error[E0277]: `Vec<_>` doesn't implement `std::fmt::Display`
  --> src/main.rs:16:20
   |
16 |         println!("{current_presents} /n");
   |                    ^^^^^^^^^^^^^^^^ `Vec<_>` cannot be formatted with the default formatter
   |
   = help: the trait `std::fmt::Display` is not implemented for `Vec<_>`
   = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead
   = note: this error originates in the macro `$crate::format_args_nl` (in Nightly builds, run with -Z macro-backtrace for more info)

Please help me debug or push me in the right direction that wouldn't be typing down 12 separate strings and printing them 1 by 1.

Upvotes: 2

Views: 6543

Answers (3)

hkBst
hkBst

Reputation: 3360

This works:

fn main() {
    let presents = [
        "A song and a Christmas tree",
        "Two candy canes",
        "Three boughs of holly",
    ];

    let mut current_presents = Vec::new();

    for (day, present) in presents.iter().enumerate() {
        current_presents.push(present);
        println!(
            "On the {} day of Christmas my good friends brought to me",
            day + 1
        );
        println!("{current_presents:?}\n");
    }
}

Upvotes: 3

will
will

Reputation: 5061

I suspect I've found a satisfying answer for my dissapointment:

 let a = [10, 20, 30, 40]; // a plain array
 let v = a.to_vec();

See manual:

Credits to coder wall:

Upvotes: 0

Swantewit
Swantewit

Reputation: 1076

The final answer looks like this (you can add all the verses up to 12th):

fn main() {
    let presents = [
        "A song and a Christmas tree",
        "Two candy canes",
        "Three boughs of holly",
        "Four coloured lights",
    ];

    for (day, _) in presents.iter().enumerate() {
        let mut presents = presents;

        let current_presents = &mut presents[0..day + 1];

        println!(
            "On the {} day of Christmas my good friends brought to me",
            day + 1
        );

        current_presents.reverse();

        current_presents
            .iter()
            .for_each(|present| print!("{} \n", present));
        println!("\n")
    }
}

Upvotes: 0

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