Simpletron is a machine that runs sml code.

Todo: Use the trick to construct salc and write tests.

References:
[Lecture 5: Computer Architecture](http://web.cs.wpi.edu/~jburge/courses/c01/cs2011/lectures/lecture5.pdf)
[A Neat C Preprocessor Trick](https://kchodorow.com/2013/08/24/a-neat-c-preprocessor-trick/)