Introducing MUPLex

I've been taking one of Dan Grossman's courses on programming languages and it was one of the most illuminating I've ever taken. While teaching, he used a made up programming language called MUPL. This MUPL had higher order functions, pairs, conditionals and the addition operation - this is the bare minimum with which you can teach how to build interpreters but also enough on which you can further build a high level functional language.

MUPLEx is basically an extensions of MUPL. It adds some syntactic sugar as well as new features. Here's a list:

• Functions with an arbitrary number of arguments
• Currying by default
• Mutability - yes, I know mutability is the source of all evil (most of it, at least) but in some cases it makes sense, like having lazy evaluation or memoization
• Records - to be able to build meaningful data structures
• More math operations
• Letrec - the equivalent of forward declaration in C (this way you can have mutually recursive functions, or other useful constructs)
• Cond - syntactic sugar for nested conditionals
• Lists - syntactic sugar for nested pairs
• A way to print out stuff
• Booleans

It also has some primitive type checking to catch some errors as you type. But, unfortunately, at this stage the errors are not too explicit.

I can't include the interpreter in this post because it's a pretty hefty beast, but I can point you to the github HTML preview thingie or directly to the repository.
*the preview may not work in Chrome/Safary