Compiling a Lisp: Lambda Lifting
14 days ago
- #python
- #compiler
- #closures
- The author revisited the Ghuloum tutorial and rewrote the implementation in Python, reducing the code to about 300 LOC compared to the original C version's 1200 LOC.
- The Python version lacks an S-expression reader and instruction encoding, opting for text assembly instead.
- The tutorial focuses on lifting lambdas, requiring recognition of variable names in 'let' and 'lambda' expressions and modifying the environment accordingly.
- A 'LambdaConverter' class is introduced to handle the conversion of expressions, keeping track of bound and free variables.
- The implementation includes handling simple constants, variables, built-in primitives, 'if' expressions, 'lambda' expressions, and 'let' expressions.
- Lambda expressions are transformed into 'code' and 'closure' forms, with free variables tracked and managed.
- The 'let' expression is handled by evaluating bindings without access to other bindings being built up, distinguishing between bound and free variables.
- Function calls are managed with special handling for primitive operators to avoid unnecessary 'funcall' forms.
- The compilation process includes generating assembly code for closures and function calls, with careful management of the stack and heap.
- The tutorial concludes with successful implementation of closures, free variable analysis, and indirect function calls in a concise Python compiler.