Macro sugars::cmap

macro_rules! cmap {
    ($key:expr => $value:expr; $i:ident <- $iter:expr) => { ... };
    ($key:expr => $value:expr; $i:ident <- $iter:expr, if $cond:expr) => { ... };
    ($key:expr => $value:expr; for $p:pat in $iter:expr) => { ... };
    ($key:expr => $value:expr; for $p:pat in $iter:expr, if $cond:expr) => { ... };
}

Macro to HashMap collection comprehensions

Supports 2 types of grammars: Haskell-like and Python-like

Limitations: Only 1 nested comprehensions and pattern support only works with python syntax

Examples:

use sugars::cmap;

let a = 10;
// Haskell-like
let x = cmap!{x => x+a; x <- 1..10};
let y = cmap!{x => x+a; x <- 1..10, if x%2 == 0};

// Python-like
let w = cmap!{x => x+a; for x in 1..10};
let z = cmap!{x => x+a; for x in 1..10, if x%2 == 0};