# ShortMaps

Implementation of a `~m` sigil for ES6-like maps in Elixir.

## Rationale

ShortMaps is the result of a
[discussion in the Elixir mailing list][google-groups]. The topic of the
discussion was the introduction of a syntax for maps similar to ES6 map syntax:

```elixir
foo = 1
bar = 2

%{foo, bar} == %{foo: foo, bar: bar}
#=> true
```

The discussion on pros and cons went on for a while until @josevalim came up
with a better solution (like he always does): using sigils.

```elixir
foo = 1
bar = 2

~m(foo bar)a == %{foo: foo, bar: bar}
#=> true
```

Sigils allow to:

- be more explicit and declarative
- use both atom and string keys (using modifiers in the sigil)

This library is an attempt to implement this so that you can try it out.

## Examples

Note that you always have to `import ShortMaps` for the sigil to work.

```elixir
import ShortMaps

my_map = %{foo: 1, bar: 2, baz: 3}

~m(foo bar baz)a = my_map
foo #=> 1
```

```elixir
import ShortMaps

name = "Meg"

# String keys by default (or with the 's' modifier)
~m(name) #=> %{"name" => "Meg"}
# Atom keys with the 'a' modifier
~m(name)a #=> %{name: "Meg"}
```

There is also support for pinning variables, if you want to do matching
vs. their previous value:

```elixir
iex(1)> import ShortMaps
nil
iex(2)> name = "Meg"
"Meg"
iex(3)> ~m(^name)a = %{name: "Meg"}
%{name: "Meg"}
iex(4)> ~m(^name)a = %{name: "Megan"}
** (MatchError) no match of right hand side value: %{name: "Megan"}
```

If you need to match on structs, the first word should be '%' followed by the
name of the module:

```elixir
iex(1)> import ShortMaps
nil
iex(2)> defmodule Foo do
...(2)>  defstruct bar: nil
...(2)>end
{:module, Foo,
 <<...>>,
 [bar: nil]}

iex(3)> ~m(%Foo bar)a = %Foo{bar: 5}
%Foo{bar: 5}
iex(4)> bar
5
iex(5)> ~m(%Foo ^bar)a = %Foo{bar: 12}
** (MatchError) no match of right hand side value: %Foo{bar: 12}
```

You can see more examples and read some docs in the docs for the `sigil_m`
macro.

## LICENSE

This is free and unencumbered software released into the public domain.

Anyone is free to copy, modify, publish, use, compile, sell, or
distribute this software, either in source code form or as a compiled
binary, for any purpose, commercial or non-commercial, and by any
means.

In jurisdictions that recognize copyright laws, the author or authors
of this software dedicate any and all copyright interest in the
software to the public domain. We make this dedication for the benefit
of the public at large and to the detriment of our heirs and
successors. We intend this dedication to be an overt act of
relinquishment in perpetuity of all present and future rights to this
software under copyright law.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
OTHER DEALINGS IN THE SOFTWARE.

For more information, please refer to <http://unlicense.org>


[google-groups]: https://groups.google.com/forum/#!topic/elixir-lang-core/NoUo2gqQR3I