# typerep-map
[](https://hackage.haskell.org/package/typerep-map)
[](https://travis-ci.org/kowainik/typerep-map)
[](https://github.com/vrom911/typerep-map/blob/master/LICENSE)
`typerep-map` introduces `TMap` and `TypeRepMap` — data structures like [`Map`](http://hackage.haskell.org/package/containers-0.6.0.1/docs/Data-Map-Lazy.html#t:Map), but where types serve as keys, and values have the types specified in the corresponding key spots.
For the more details on the implementation see [this blog post](https://kowainik.github.io/posts/2018-07-11-typerep-map-step-by-step).
## Usage example
```haskell
ghci> import Data.TMap
ghci> tm = insert True $ one (42 :: Int)
ghci> size tm
2
ghci> res = lookup tm
ghci> res :: Maybe Int
Just 42
ghci> res :: Maybe Bool
Just True
ghci> res :: Maybe String
Nothing
ghci> lookup (insert "hello" tm) :: Maybe String
Just "hello"
ghci> member @Int tm
True
ghci> tm' = delete @Int tm
ghci> member @Int tm'
False
```
## Benchmarks
Tables below contain comparision with `DMap TypeRep` of ten `lookup` operations
on structure with size `10^4`:
| | ghc-8.2.2 | ghc-8.4.3 |
|----------------|-----------|-----------|
| `DMap TypeRep` | 517.5 ns | 779.9 ns |
| `typerep-map` | 205.3 ns | 187.2 ns |
ghc-8.2.2 | ghc-8.4.3
:---------:|:-----------:
 | 
 | 