Macro for Python-esque list comprehensions in Rust.
The c! macro implements list and hashmap comprehensions similar to those found in Python,
allowing for conditionals and nested comprehensions.
# Python Syntax
```python squares = [x*x for x in range(10)]
even_squares = [x*x for x in range(10) if x % 2 == 0]
squares_dict = {key:key*key for key in range(10)} ```
# c! Syntax
```rust let squares = c![x*x, for x in 0..10];
let even_squares = c![x*x, for x in 0..10, if x % 2 == 0];
let squares_hashmap = c!{key => key*key, for key in 0..10};
```
Note c!'s has the comprehension's parts, comma-separated.
# Examples
Simpe comprehension
```rust #[macro_use(c)] extern crate cute;
let v = [1,2,3,4]; let v_squared = c![x*x, for x in v];
``` Conditional filtering
rust
let squares = c![x*x, for x in 0..10, if x % 2 == 0];
assert_eq!(squares, vec![0, 4, 16, 36, 64]);
Nested Comprehensions
rust
let nested = vec![vec![1,2,3], vec![4,5,6], vec![7,8,9]];
let flat: Vec<usize> = c![x, for x in y, for y in nested];
assert_eq!(flat, vec![1, 2, 3, 4, 5, 6, 7, 8, 9]);
rust
let nested = vec![vec![1,2,3], vec![4,5,6], vec![7,8,9]];
let even_flat: Vec<usize> = c![x, for x in y, for y in nested, if x % 2 == 0];
assert_eq!(even_flat, vec![2, 4, 6, 8]);
Comprehensions over Iterators
rust
let vec: Vec<i32> = vec![-4, -2, 0, 2, 4];
let output: Vec<i32> = c![x*2, for x in vec.iter()];
assert_eq!(output, vec![-8, -4, 0, 4, 8]);
rust
let vec: Vec<i32> = vec![-4, -2, 0, 2, 4];
let output: Vec<i32> = c![x, for x in vec.iter(), if *x >= 0i32];
assert_eq!(output, vec![0, 2, 4]);
Function Application
rust
let vec: Vec<i32> = vec![-4, -2, 0, 2, 4];
let output: Vec<i32> = c![x.abs(), for x in vec.iter()];
assert_eq!(output, vec![4, 2, 0, 2, 4]);
```rust fn square(x:i32) -> i32 { x*x }
let vec: Vec
HashMap Comprehensions (Dictionary Comprehensions)
```rust // simple hashmap comprehension
let squares_hashmap = c!{key => key*key, for key in 0..10};
```
```rust // hashmap comprehension from an Iterator // NOTE: we have to perform dereferencing: *key
let map = c!{key => keykey, for key in vec![1,2].iter()};
```
```rust // conditional hashmap comprehension
let v: Vec<(&str, i32)> = vec![("one", 1), ("two", 2), ("three", 3)]; let map = c! {key => val, for (key, val) in v, if val == 1 || val == 2};
let mut expected: HashMap<&str, i32> = HashMap::new(); expected.insert("one", 1); expected.insert("two", 2);
assert_eq!(map, expected); ```
```rust // conditional hashmap comprehension from an Iterator // NOTE: we perform deferencing when using values
let map = c! {key => keykey, for key in vec![1,2].iter(), if *key % 2 == 0};
let mut e: HashMap
assert_eq!(map, e); ```