Created Writing a Macro (markdown)

Writing-a-Macro.md

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+Macros are complex and powerful, allowing you to build the AST imperatively. So how does one build AST? It's not as hard as it sounds.
+
+I'm going to go over the process I used to write the marshaling macro used in keineSchweine (github/fowlmouth/keineSchweine/lib/genpacket.nim) 
+
+Okay, so I have described a packet as a object type holding the information needed, for example a packet that gets sent out to clients when a new client connects might look like this:
+```nimrod
+type TClientJoined = object
+  playerID: int
+  alias: string
+```
+
+To make this useful, I'd like to build the TClientJoined with the information needed and write it a stream, and have a function that takes a stream and reads from it into a TClientJoined
+```nimrod
+# writeBE and readBE are reading/writing functions that will read/write in big endian 
+proc write (packet: var TClientJoined; stream: PStream) =
+  writeBE stream, packet.playerID
+  writeBE stream, packet.alias
+proc readClientJoined (stream: PStream): TClientJoined = 
+  readBE stream, result.playerID
+  readBE stream, result.alias
+```
+
+