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#[macro_export]
macro_rules! hash_map {
() => { std::collections::HashMap::with_capacity(16) };
($key: expr => $value: expr) => {
hash_map!($key => $value; 16)
};
($key: expr => $value: expr; $init_capacity: expr) => {
{
let mut hash_map = std::collections::HashMap::with_capacity($init_capacity);
hash_map.insert($key, $value);
hash_map
}
};
($($key: expr => $value: expr),*) => {
vec![$(($key, $value)),*].into_iter().collect::<std::collections::HashMap<_, _>>()
};
($($key: expr => $value: expr,)*) => {
hash_map!($($key => $value),*)
};
}
#[cfg(test)]
mod test {
use std::collections::HashMap;
#[test]
fn test_hash_map_macro_without_params() {
let expected: HashMap<i32, i32> = HashMap::with_capacity(16);
let product: HashMap<i32, i32> = hash_map!();
assert_eq!(expected, product);
}
#[test]
fn test_hash_map_macro_with_one_param() {
let mut expected = HashMap::with_capacity(16);
expected.insert("hello", "world");
let product = hash_map!("hello" => "world");
assert_eq!(expected, product);
}
#[test]
fn test_hash_map_macro_with_capacity() {
let mut expected = HashMap::with_capacity(20);
expected.insert("hello", "world");
let product = hash_map!("hello" => "world"; 20);
assert_eq!(expected, product);
}
#[test]
fn test_hash_map_macro_with_any_params() {
let mut expected = HashMap::with_capacity(16);
expected.insert("hello", "world");
expected.insert("world", "hello");
let product = hash_map! {
"hello" => "world",
"world" => "hello",
};
assert_eq!(expected, product);
}
#[test]
fn test_hash_map_macro_with_any_params_and_without_trailing_comma() {
let mut expected = HashMap::with_capacity(16);
expected.insert("hello", "world");
expected.insert("world", "hello");
let product = hash_map! {
"hello" => "world",
"world" => "hello"
};
assert_eq!(expected, product);
}
}