The code of this interpreter is based on source code accompanying Pierce's excellent book _Types and Programming Languages_. (In particular, the files here <http://www.cis.upenn.edu/~bcpierce/tapl/checkers/fulluntyped/>.) We aggressively modified that code to suit our somewhat different needs (and taste). Notably, Pierce's code only provides a substitute-and-repeat interpreter; so part of our refactoring was to make it easier to switch back and forth between that and an environment-based interpreter.
-We provided you with a [[homework assignment|/exercises/assignment7]] that is a simplified version of the code of our interpreter. After getting that to work, you may be interested to play around with the fuller version, which adds literal numbers and booleans, and user-friendly input and printing of results.
+We provided you with a [[homework assignment|/exercises/assignment6-7]] that is a simplified version of the code of our interpreter. After getting that to work, you may be interested to play around with the fuller version, which adds literal numbers and booleans, and user-friendly input and printing of results.
But these benefits come at a price. The code has some complexity to it.