Lab1.
Lab2.
my solution to lab1
Merge Lab1
Finish Lab2 exercise2
Finish exercise3
Finish Lab2 exercise4
Finish exercise5 but existence some bugs
Finish exercise 5
Finish exercise6
Finish exercise7
Finish exercise8
tiny
Finish exercise9
Modify .gitignore
:Merge branch 'Lab2' into Lab3

Conflicts:
	src/Tiger.java
	src/ast/Fac.java
	src/elaborator/ElaboratorVisitor.java
Add '}' in ElaboratorVisitor.java
lab3 init
Finish lab3 exercise2
Finish lab3 exercise7