https://github.com/vic/having
Haskell like `where` sugar for Elixir. A pipe-able `with` special form.
https://github.com/vic/having
elixir syntax-experiment
Last synced: 8 months ago
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Haskell like `where` sugar for Elixir. A pipe-able `with` special form.
- Host: GitHub
- URL: https://github.com/vic/having
- Owner: vic
- Created: 2016-11-26T10:31:17.000Z (over 9 years ago)
- Default Branch: master
- Last Pushed: 2017-02-20T23:02:24.000Z (over 9 years ago)
- Last Synced: 2024-08-12T08:04:26.787Z (almost 2 years ago)
- Topics: elixir, syntax-experiment
- Language: Elixir
- Size: 5.86 KB
- Stars: 7
- Watchers: 3
- Forks: 2
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# Having
[](https://twitter.com/vborja)
Haskell like `where` sugar for Elixir. A pipe-able `with` special form.
## Usage
```elixir
import Having
```
The `having` macro is a tiny syntax sugar around `with`. To make it work a bit
like the `where` keyword for Haskell, where you can have an expression and
then some bindings for evaling it on.
For example, the following Haskell code
```haskell
a + b
where
a = 3
b = a * a
```
Could be written in Elixir like:
```elixir
iex> a + b
...> |> having(a: 3, b: a * a)
12
```
that will be compiled into:
```elixir
with a = 3,
b = a * a,
do: a + b
```
Every `having` gets rewritten into a corresponding `with` special form.
And thus can have its own `else:` clauses, guards on `<-` just like `with`.
For example if you pipe an expression into two `having`s:
```elixir
{a, b}
|> having(a = b * b)
|> having(b when b < 10 <- 2)
```
will get rewritten to:
```elixir
with(b when b < 10 <- 2) do
with(a = b * b) do
{a, b}
end
end
```
Note that in the `having` example, the expression you want to compute
is the first thing you see, instead of it being nested inside `with` forms.
Also note that the most external `with` corresponds to the latest piped `having`
this is important if you need to have some values that depend on others.
For more examples look at the documentation of [having.ex](https://github.com/vic/having/blob/master/lib/having.ex)
## Installation
[Available in Hex](https://hex.pm/packages/having), the package can be installed as:
1. Add `having` to your list of dependencies in `mix.exs`:
```elixir
def deps do
[{:having, "~> 0.1.0"}]
end
```
2. Ensure `having` is started before your application:
```elixir
def application do
[applications: [:having]]
end
```