Pattern combinator (#1105)

*  init

*  add pattern

combinator/README.md

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+---
+layout: pattern
+title: Combinator
+folder: combinator
+permalink: /patterns/combinator/
+categories: Behavioral
+tags:
+ - Functional
+ - Reactive
+ - Idiom
+---
+
+## Also known as
+Composition pattern
+
+## Intent
+The functional pattern representing a style of organizing libraries centered around the idea of combining functions.  
+Putting it simply, there is some type T, some functions for constructing "primitive" values of type T, 
+and some "combinators" which can combine values of type T in various ways to build up more complex values of type T.
+
+
+## Applicability
+Use the combinator pattern when:
+- You are able to create a more complex value from more plain values but having the same type(a combination of them)
+
+## Real world examples
+- java.util.function.Function#compose
+- java.util.function.Function#andThen
+
+## Credits
+- [Example for java](https://gtrefs.github.io/code/combinator-pattern/)
+- [Combinator pattern](https://wiki.haskell.org/Combinator_pattern)
+- [Combinatory logic](https://wiki.haskell.org/Combinatory_logic)