Declarative map! and set! macros.
The map! macro allows for statically initializing a
std::collections::HashMap.
The same goes for the set! macro only for
std::collections::HashSet.
The macros are equivalent to the vec! macro offered by the rust
standard library for initializing Vec instances.
This crate has zero dependencies.
Some languages provide a neat way for creating non-empty maps/dictionaries. For example, in python you can create a non-empty map by running the following code:
python
hello = {
"en": "Hello",
"de": "Hallo",
"fr": "Bonjour",
"es": "Hola",
}
In rust, creating a non-empty map (rust has a built-in type in the
standard library for creating hash maps std::collections::HashMap)
is not as straight-forward:
```rust use std::collections::HashMap;
let mut hello = HashMap::new();
hello.insert("en", "Hello"); hello.insert("de", "Hallo"); hello.insert("fr", "Bonjour"); hello.insert("es", "Hola"); ```
More less-readable boilerplate code is needed in rust to create a
non-empty map.
Even worse, hello must be declared as mutable, even if we do not
want it to be mutable after we have added our four entries.
The map-macro crate offers a better way of declaring non-empty
maps, with the map! macro.
Creating the same hello map from the example above can be simplified
to:
```rust use map_macro::map;
let hello = map! { "en" => "Hello", "de" => "Hallo", "fr" => "Bonjour", "es" => "Hola", }; ```
That is it.
Looks nearly as neat as the python version with the added benefit
that hello is not mutable after we have created it.
The map! macro is powerful enough to create maps from non-static
keys and values as well, you are not limited to literals.
You can create a map like this:
```rust use map_macro::map;
fn helloinfrench() -> &'static str { "Bonjour" }
fn spanishlanguagecode() -> &'static str { "es" }
let hello = map! { "en" => "Hello", "de" => "Hallo", "fr" => helloinfrench(), spanishlanguagecode() => "Hola", }; ```
Empty maps can be created as well, but must provide type hints for the compiler:
```rust use std::collections::HashMap; use map_macro::map;
let hello: HashMap<&str, &str> = map! {};
assert_eq!(hello.len(), 0); ```
Rust's standard library provides a similar macro for creating vectors,
vec!.
map-macro offers the equivalent macros for creating maps and sets.
Rust has the same cumbersome creation process for creating sets (in
rust sets are provided by the standard library, too, via the
std::collections::HashSet struct).
In python you can create a set like this:
python
x = set([1, 2, 3])
Not as neat as a map, but still quite concise. Dart even comes with syntactic sugar for creating a set:
dart
final x = {1, 2, 3};
In rust, you would have to write:
```rust use std::collections::HashSet;
let mut x = HashSet::new();
x.insert(1); x.insert(2); x.insert(3); ```
The set! macro provided by the map-macro crate lets you write the
same code as:
``` use map_macro::set;
let x = set! { 1, 2, 3 }; ```
Again, nearly as neat as Dart!
The set! macro is as powerful as the map! macro:
```rust use map_macro::set;
fn one() -> i32 { 1 }
let x = set! { one(), 2, 3 }; ```
```rust use std::collections::HashSet; use map_macro::set;
let x: HashSet
assert_eq!(x.len(), 0); ```