[msla]

This is pointedly not about the Old Techniques in compiler writing.

For example, the author doesn't divide the compiler into multiple passes, so it can fit in RAM; he assumes you have "enough" RAM for a simple compiler to fit, and goes from there.

Similarly, he jumps right into recursive code, because that's simpler, and he assumes your computer has a stack of reasonable depth. (Go back far enough and computers had really shallow stacks. Go back farther and computers didn't have call stacks at all.)

Finally, his compiler doesn't optimize the code, because he assumes that the obvious code will run sufficiently fast. A fairly modern idea, and one which removes the complexity which would otherwise drive the design and force things like multiple passes and complex internal representation.