Mostly goes over compiling the AST to a custom stack machine. Standard stuff.

• direnv: tool to make it easy to change environment variables dependent on which directory you are in.
• Von Neumann architecture
• Call stack: keeps track of program counters during function calls; needed so when one call ends we know where to return to.
• Symbol table: associates names (the symbol) with information. For example keeps track of which register the value of 'foo' is presently kept in.

• direnv tool

Closures

• Closure: a function which carrys a pointer to an environment object.
• Environment: a collection of slots that must persist along with the life of a closure.
• Free variable: a variable which lives outside of a closure yet is touched by it; a reference must be kept in the environment.