[Origin of MapleFE]

This project is to create a programming language frontend, which leverages 'Autogen' to complete
most of work of lexing and parsing. The origin of this project is coming from the history in our parst twenty
years of work in compiler and programming languages. We are tired of the tons of modifications of existing
opensource frontend project like Clang, if we want to do something in new language features. So we decided to
have our own frontend, which could be easier to handle new languages.

[Key points]

1. Autogen is the key idea which automatically generates lexing/parsing data structures in .h/.cpp files which
   are further included in the language frontend. The language implementors write .spec files describing the
   language specifications under the language directory, such as java/.
2. The parsing algorithm is named Wavefront. The rules are categorized into recursions, and recursions are
   combined into group if they reach each other. The Wavefront parsing is working on the recursion group.
   It works wave by wave until it reaches the fixed point.

[Source code directory]

1. Most programming languages have very similar syntax, so it's very helpful to put
   the shared part into a common directory. shared/ is for this usage. It contains
     a) shared data structures representing shared syntax;
     b) shared parser/translater components; 
2. Language specific parts are in their own directory, such as java/. It contains some special part of this
   language, the language .spec files, and gen_xxx.h/gen_xxx.cpp which are generted by autogen.
3. The tool autogen is under autogen/
4. The tool recdetect is under recdetec/. It's used to find the recursions and recursion groups.

[Preparation]

https://gitee.com/openarkcompiler/OpenArkCompiler/blob/master/doc/en/DevelopmentPreparation.md
Follow the instruction in "Recommended Development Environment" section to get tools installed

The following packages also need to be installed:
```bash
sudo apt install -y clang-tools-10 clang-format-10 python3 libyaml-cpp-dev
```

[How to build]

1. source envsetup.sh [java|typescript]
2. make mapleall
   This step is to build mapleall (Maple IR related libraries). If you have done it once,
   you dont need do it again unless you changed the code in mapleall.
3. make
4. If you are working at Java frontend, you will see output/java/java/java2mpl. This is the executable
   frontend.
4. If you are working at Typescript frontend, you will see output/typescript/bin/ts2ast. This is the executable
   frontend. You can also see output/typescript/bin/ast2cpp, which translate AST to cpp source code.

[How to test]

1. make test

run a single test, say t1.java:
1. cd test
2. make t1

You can find all Java test cases in test/java.
You can find all Typescript test cases in test/typescript.