Re-Reika: Engineering a DSL compiler

• #48 As usual, report driven development, finished at 2017/12/15 (the deadline of submitting report)
• introduced new compiler package, split into multiple phases, tried to add module and standard library
• scope, symbol table etc. still lacks the basic structure

Re:Reika

• finish the talk on CMPS 253 #32
• add example for handling negative number and using visitor pattern in playground

Primitive Types

• support int, double, bool
• negative number using unary expression #18
• use visitor for type checker #27, remember to have accept in every subclass of node
• support let x = 1 and let x:Int = 1, user specified type is used as extra constraint, no type inference #26 is needed