A toy programming language built in Haskell. This was originally written as a part of a course on programming language semantics. For the course version I also wrote a static analysis tool which used symbolic execution to automatically detect errors in Tills source code.
Since the course I have added some features to this language, such as the ability to perform IO. I used this feature to solve some basic programming problems on Kattis. Because Tills is so small, I was able to upload the entire Haskell interpreter as well as the the Tills source code for the programming puzzle I was solving :-).
The implementation is inspired by the chapter on monadic parsing in Graham Hutton's Programming in Haskell and the semantics of the "While" programming language outlined in Nielson and Nielson's Semantics with Applications: An Appetizer
The implementation is split into three files:
- combinators.hs: A set of parser combinators which can turn parts of strings into parts of abstract syntax trees (ASTs).
- parser.hs: The parser for the Tills language. This file defines how to turn Tills source code into an AST.
- am.hs: The abstract machine which runs Tills programs. This file uses the parser to convert source files into ASTs, then defines the rules for executing these ASTs.
The samples directory contains a collection of Tills programs which solve various contrived problems.