SHF: Small: An Extensible Gradual Type System via Compile-Time Meta-Programming

许多现代编程语言都属于“脚本语言”一类。“这些语言特别灵活，它们允许程序员快速组装程序的各个部分来解决问题。不幸的是，脚本语言的灵活性也会阻碍程序员在脚本发展成更大的程序时开发和维护脚本的能力。随着脚本语言变得越来越流行，特别是对于新的程序员来说，长期的开发和维护问题影响着我们计算基础设施的许多层中越来越多的程序。这个项目是关于通过将类型系统引入脚本语言来平滑从脚本到更严格的编程风格的路径。类型系统可以提供关于程序将如何执行的预先保证，并且它可以帮助隔离程序修改的影响。然而，这个项目的目标不是强加一个特定的类型系统，而是探索一种定义和定制类型系统的特定方法，同时将其逐渐引入现有程序。该项目中的特定技术方法建立在PLT Scheme编程语言提供的Lisp风格的宏之上。

Many modern programming languages fit in a category called "scripting languages." These languages are especially flexible, and they allow a programmer to quickly assemble pieces of a program to solve a problem. Unfortunately, a scripting language's flexibility can also hinder the programmer's ability to develop and maintain a script when it grows into a larger program. As scripting languages have become more popular, especially with new programmers, long-term development and maintenance problems affect a growing body of programs at many layer of our computing infrastructure. This project is about smoothing the path from scripts to a more rigorous style of programming by introducing type systems into scripting languages. A type system can offer up-front guarantees about how a program will execute, and it can help isolate the effects of program modifications. Rather than imposing a particular type system, however, this project's goal is to explore a particular way of defining and customizing a type system while introducing it gradually into an existing program. The specific technical approach in this project builds on Lisp-style macros as provided by the PLT Scheme programming language.