50.4 Function exercises

source bash-setup.sh

50.4.1First program¶

We first create the binary project using cargo:

cargo init factorial

    Creating binary (application) package

note: see more `Cargo.toml` keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

Then we enter the folder:

cd factorial

cat >src/main.rs <<EOF
fn fact(n: u64) -> u64 {
  if n > 1 {
    n * fact(n - 1)
  } else {
    1
  }
}

fn main() {
  println!("{}", fact(20));
}
EOF

And modify the main code file as follow, with a function fact() called by the main() function:

bat src/main.rs

fn fact(n: u64) -> u64 {

  if n > 1 {

    n * fact(n - 1)

  } else {

    1

  }

}

fn main() {

  println!("{}", fact(20));

}

Finally, we build & execute:

cargo run

   Compiling factorial v0.1.0 (/tmp/tmp.cBdauJcdkl/factorial)

    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.16s

     Running `target/debug/factorial`

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