argio

A macro to convert function input and output to stdio

This macro changes the arguments and return value of a function to take them from standard input and output.

#[argio]
fn main(n: i32) -> i32 {
    n * 2
}

Instead of taking an integer as an argument, this function reads an integer from the standard input and outputs the result to the standard output.

Because this macro uses proconio as a backend for input, you can put the same arguments as those that can be passed to the input! macro of proconio in the function (even if they are not the correct syntax for Rust).

#[argio]
fn main(n: usize, x: [i64; n]) -> i64 {
    x.into_iter().sum()
}

This function takes such an input

N
x_1 x_2 ... x_N

from the standard input and outputs the sum to the standard output.

You can change the macro for the input by setting the input parameter. A macro takes the arguments of the function as they are.

macro_rules! my_input {
    ...
}

#[argio(input = my_input)]
fn main(n: usize, x: [i64; n]) -> i64 {
    x.into_iter().sum()
}

Because the Display trait is used to display the return value, functions such as Vec which does not implement the Display trait cannot be compiled as it is.

You can customize the behavior of the output by using a wrapper struct that implements the Display trait.

struct Wrap<T>(T);

impl<T: Display> Display for Wrap<Vec<T>> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        for (ix, r) in self.0.iter().enumerate() {
            if ix > 0 {
                write!(f, " ")?;
            }
            r.fmt(f)?;
        }
        Ok(())
    }
}

#[argio]
fn main(n: usize) -> Wrap<Vec<usize>> {
    Wrap((0..n).map(|i| i * 2).collect())
}

$ echo 10 | cargo run
0 2 4 6 8 10 12 14 16 18

Of course, you can also output manually. If the return value of the function is (), it does not output anything to the standard output, so you can output it manually and return ().

#[argio]
fn main(n: usize) {
    let ans = (0..n).map(|i| i * 2).collect::<Vec<_>>();
    for (i, x) in ans.into_iter().enumerate() {
        if i > 0 {
            print!(" ");
        }
        print!("{}", x);
    }
    println!();
}

You can also specify a wrapper for the output from a macro parameter. This has the advantage of removing information about the wrapper from the code, allowing you to move the output customization to the template part of the code.

#[argio(output = Wrap)]
fn main(n: usize) -> Vec<usize> {
    (0..n).map(|i| i * 2).collect()
}

If multicase is specified as an attribute, it can be used to automatically execute multiple inputs for multiple cases that start with the number of cases.

The value of the attribute multicase is a string to be displayed at the top of each case. The variable i contains the case number of 0 origin, so you can customize the display by using it.

#[argio(multicase = "Case #{i+1}: ", output = Wrap)]
fn main(n: usize) -> Vec<usize> {
    (0..n).map(|i| i * 2).collect()
}

$ echo "3 2 3 5" | cargo run
Case #1: 0 2
Case #2: 0 2 4
Case #3: 0 2 4 6 8

License: MIT