DMN FEEL脚本实现分析

Drools的实现

https://github.com/kiegroup/drools/tree/main/kie-dmn/kie-dmn-feel：

antlr4词法解析，通过vistor生成抽象语法树，执行。但是可以用javaparser将ast生成java代码，再编译成class执行。其原理效果还不太明确。

例子：
https://stackoverflow.com/questions/29971097/how-to-create-ast-with-antlr4

camunda的实现

https://camunda.github.io/feel-scala/:

用的scala实现
readme里有一段最近被删掉了。
The following resources can help to understand some general concepts behind the implementation:

• Build your own Programming Language with Scala
• Easy Parsing with Parser Combinators
• FastParse - Documentation of the Parser Library