Analyzes dynamically typed languages (like JavaScript or Python) as a special, single-typed subset of static languages. The Practical Value of Programming Language Theory
The study includes sophisticated mechanisms like exceptions, continuations, and mutable state, analyzing how these features impact the purity and predictability of a language. Conclusion: Why Foundations Matter
The universal language of functions. It strips programming down to its absolute bare essentials: variable binding, function abstraction, and function application. 15-312 explores both the untyped and simply-typed variants. Product and Sum Types 15312 foundations of programming languages
: If a well-typed program takes an execution step, the resulting program has the exact same type as before.
If a language possesses both properties, it is mathematically guaranteed never to crash due to undefined behaviors like executing a string as a function. 4. Advanced Language Features It strips programming down to its absolute bare
Before you can evaluate a program, you must represent it. While standard compiler courses focus heavily on parsing source code into Abstract Syntax Trees (ASTs), 15-312 introduces a more powerful concept: .
Understanding the is essential for several reasons: If a language possesses both properties, it is
The rules of type systems that predict program behavior before execution.
As the course progresses, it moves beyond basic arithmetic and functions into complex computational mechanisms used in modern production languages. Continuations and Control Flow
A Type⟺A Mathematical PropositionA Type ⟺ A Mathematical Proposition
ABTs build scope directly into the syntax representation. They mechanically handle alpha-equivalence and (ensuring that substituting a variable into a new scope doesn't accidentally change its meaning because of a name collision). By mastering ABTs, language designers avoid the common pitfalls of scope confusion that plague early language implementations. 3. Statics vs. Dynamics