Added another use-case for the prefix types SIP (#942)

* Splitting SIP33

* New SIP files

* Updates SIP 33 and new SIP-NN(prefix types)

* Added updated PR links

* redundant file

* Update to prefix types SIP, according to feedback on the PR.

* Update to SIP33 and added example to prefix types use

* Minor grammer change.

* Update history table

* Added use-case for prefix type `~`

Author: soronpo

_sips/sips/2017-10-25-adding-prefix-types.md

@@ -15,7 +15,7 @@ permalink: /sips/:title.html
 | ------------- | ---------------------------------------- |
 | Oct 25th 2017 | Split prefix types from [SIP33](http://docs.scala-lang.org/sips/priority-based-infix-type-precedence.html), and emphasize motivation |
 | Nov 29th 2017 | Updated SIP according to feedback in the PR, and recent update to SIP23 |
-
+| Dec 1st 2017  | Added another use-case for prefix type `~` |
 
 Your feedback is welcome! If you're interested in discussing this proposal, head over to [this](https://contributors.scala-lang.org/t/sip-nn-make-infix-type-alias-precedence-like-expression-operator-precedence/471) Scala Contributors thread and let me know what you think.
 
@@ -60,6 +60,9 @@ It is easier to reason about the language when mathematical and logical operatio
 
 ### Motivating examples
 
+#### Splice prefix types for meta-programming
+A requirement for `unary_~` is described by Martin Odersky at [this proposal](https://gist.github.com/odersky/f91362f6d9c58cc1db53f3f443311140).
+
 #### Singleton-ops library example
 
 The [singleton-ops library](https://github.com/fthomas/singleton-ops) with [Typelevel Scala](https://github.com/typelevel/scala) (which implemented [SIP-23](http://docs.scala-lang.org/sips/pending/42.type.html)) enable developers to express literal type operations more intuitively.