# DecimalEnv

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This library provides two macros to be able to use `Decimal`s with regular
Elixir operators i.e.

```elixir
iex(1)> import DecimalEnv
iex(2)> decimal do
...(2)>   21.0 + "21.0"
...(2)> end
#Decimal<42.0>
```

It is possible to provide a decimal context as argument for the macro i.e

```elixir
iex(1)> import DecimalEnv
iex(2)> decimal [precision: 2] do
...(2)>   1 / 3
...(2)> end
#Decimal<0.33>
```

> For more information about context check `Decimal.Context` struct in
> `Decimal` repository.

Not all the Elixir statements are valid. The purpose of these macros is to
make it easier to write formulas involving `Decimal` type, so writing Elixir
code inside the `decimal` block is discouraged i.e.

```elixir
iex(1)> import DecimalEnv
iex(2)> Enum.reduce([10.99, 10.01, 20.99, 0.01], 0.00,
...(2)>   fn x, acc ->
...(2)>     decimal do: x + acc
...(2)>   end)
#Decimal<42.00>
```

The previous example calculates the sum of a list of `Float`s, but returns
the result as a `Decimal` type. The code is more clear than its equivalent
without the macro:

```elixir
iex(1)> Enum.reduce([10.99, 10.01, 20.99, 0.01], Decimal.new(0.00),
...(2)>   fn x, %Decimal{} = acc ->
...(2)>     Decimal.add(Decimal.new(x), acc)
...(2)>   end)
#Decimal<42.00>
```

The only statement offered is `if` statement i.e:

```elixir
iex(1)> import DecimalEnv
iex(1)> a = 42.0
iex(3)> decimal do
...(3)>   if a > 10, do: a, else: 10
...(3)> end
#Decimal<42.0>
```

> The guard in the `if` statement should be a decimal comparison.

It is posible to assign variables inside the block, but pattern matching is
not available i.e:

```elixir
iex(1)> import DecimalEnv
iex(2)> decimal [precision: 2] do
...(2)>   a = div(42.1, 2.0)
...(2)>   a * 2
...(2)> end
#Decimal<42>
```

> Constant values inside the decimal block are precalculated at compile time.

## Installation

Add it to your `mix.exs`

```elixir
def deps do
  [{:decimal_env, "~> 0.2"}]
end
```

## Author

Alexander de Sousa.

## License

`DecimalEnv` is released under the MIT License. See the LICENSE file for
further details.