added a short coding style guide

.gitignore

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 *.~undo-tree~
 *.dSYM~
+*#*

docs/#coding-style.md#

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-# These are more like guidelines

docs/.#coding-style.md

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-peisongxiao@PeisongXiao.11477

docs/coding-style.md

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+# These are more like guidelines
+
+## Naming schemes
+- Use reasonable names, especially for class members
+- Use shortened names for local variables
+- Use comments to explain if a name doesn't obviously imply what the
+  variable does
+  
+## Constants and types
+- All constant variables should be in all CAPS
+- When not needing values to distinguish flags (i.e. the flag is only
+  there to denote a type, its value can be anything), use **enum**.
+- If a template object is used more than once, it is a good idea to
+  wrap it in a class/struct or use a **typedef**
+- If the purpose of a class is solely to store data, use a struct.
+
+## Object design
+- If an object isn't meant to be inherited, declare it **final**
+- If a member function has to be implemented individually, declare it
+  as a pure virtual function.
+
+## Global variables
+- Avoid using global variables at all costs
+- Can improve **rng** to be referenced instead of externally exported
+
+## Functions and local variables
+- A function should be at most 40 lines unless it's logically simple
+  (e.g. has a long switch statement that calls other functions).
+  *rationale: functions should be short and sweet and let the people
+  reading them know what it does.*
+- Never have more than 4 local variables in the scope of a function at
+  the same time.
+  *rationale: a normal human's brain can only keep track of a handful
+  of things at once*
+
+## STL library
+- Prefer using the STL library over raw data types unless it's a very
+  simple data type
+- Use unique_ptr<> for heap-allocated objects