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Merge pull request #275 from davidchambers/group
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fix Group laws
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davidchambers authored Oct 13, 2017
2 parents 9d5eaa8 + e6be33c commit a448761
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5 changes: 3 additions & 2 deletions README.md
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Expand Up @@ -312,14 +312,15 @@ Given a value `m`, one can access its type representative via the
A value that implements the Group specification must also implement
the [Monoid](#monoid) specification.

1. `g.concat(g.invert())` is equivalent to `g.empty()` (right inverse)
2. `g.invert().concat(g)` is equivalent to `g.empty()` (left inverse)
1. `g.concat(g.invert())` is equivalent to `g.constructor.empty()` (right inverse)
2. `g.invert().concat(g)` is equivalent to `g.constructor.empty()` (left inverse)

#### `invert` method

```hs
invert :: Group g => g ~> () -> g
```

A value which has a Group must provide an `invert` method. The
`invert` method takes no arguments:

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