🍕 LOX - Crafting Interpreters (Java)

• cd monkey_parser && cargo test --package monkey_parser --bin monkey_parser `

🍕 MONKEY - Write Your Own Interpreter (Go)

• cd lox_parser && cargo test --package lox_parser --bin lox_parser

estructura ✨

• grammars: contiene poc's de PEG con la librería pest

• lox parser:

  • minimal parser for 1 - (2 * 3) < 4 == false
  • a more procedural / imperative code style
  • uses a top down parser
  • ✅ let variables
  • ✅ loops
  • ✅ block scope
  • ✅ functions
  • ✅ semantic analysis aka resolver pass
  • ✅ closures
  • ✅ classes
  • ✅ inheritance

• monkey parser:

  • a more object oriented code style
  • uses a pratt parser

• linked_list: since block scoping is similar to a linked-list, I will take tour on this

  • following: https://rust-unofficial.github.io/too-many-lists/index.html
  • at the end it seems we can use the great old rust vec!
  • learnings:
    • std:collection -> LinkedList
    • DoubleEndedIterator trait applied in vec or linked list
    • https://rust-lang.github.io/rfcs/2570-linked-list-cursors.html#rationale-and-alternatives
    • IterMut trait

semantic analysis

• Write a chunk of code that inspects the user’s program, finds every variable mentioned, and figures out which declaration each refers to.
• after parsing and before interpreting, any work that doesn’t rely on state that’s only available at runtime can be done in this way.
• Variable resolution touches each node once, so its performance is O(n) where n is the number of syntax tree nodes. More sophisticated analyses may have greater complexity, but most are carefully designed to be linear or not far from it. It’s an embarrassing faux pas if your compiler gets exponentially slower as the user’s program grows.

tokens

• stateful: literal value, line

parser

• ast creation
• error handling (logging them or accumulating then displaying them)
  • synchronization

statements

• Functions return values.
• Procedures cannot return values.
• print statement evaluates an expression and displays the result to the user
  • BASIC and Python have dedicated print statements and they are real languages. Granted, Python did remove their print statement in 3.0 . . .
  • why it is bad?

evaluation

• walking recursively the ast tree (slow)
• conversion into bytecode (fast)
  • like ruby >1.9

data types

• primitives: int, byte, short, char
• references: compound data structures