Architecture Overview¶

The FOOL compiler is structured as a classic multi-phase pipeline. Each phase transforms its input and passes the result to the next phase.

Source text
    │
    ▼
┌──────────────┐
│   Lexer &    │  ANTLR-generated from FOOL.g4
│   Parser     │
└──────┬───────┘
       │  Parse Tree
       ▼
┌──────────────┐
│  AST         │  ASTGenerationSTVisitor
│  Generation  │
└──────┬───────┘
       │  AST (Node hierarchy)
       ▼
┌──────────────┐
│  Symbol      │  SymbolTableASTVisitor
│  Table       │
└──────┬───────┘
       │  Enriched AST (EAST) – nodes annotated with STentry
       ▼
┌──────────────┐
│  Type        │  TypeCheckEASTVisitor
│  Checking    │
└──────┬───────┘
       │  Type-checked EAST
       ▼
┌──────────────┐
│  Code        │  CodeGenerationASTVisitor
│  Generation  │
└──────┬───────┘
       │  SVM assembly
       ▼
   .fool.asm

Key Classes¶

Class	Role
`FOOL.g4`	ANTLR grammar defining the language syntax
`AST.java`	Defines all AST node types as static inner classes
`ASTGenerationSTVisitor`	Visits the Parse Tree and builds the AST
`SymbolTableASTVisitor`	Builds the symbol table and enriches the AST
`TypeCheckEASTVisitor`	Performs type checking on the enriched AST
`CodeGenerationASTVisitor`	Generates SVM assembly from the AST
`PrintEASTVisitor`	Pretty-prints the enriched AST (debugging aid)
`STentry`	Holds a symbol-table entry (type, nesting level, offset)
`TypeRels`	Encodes subtype relationships between types
`Test`	Entry point: orchestrates all compiler phases

Visitor Pattern¶

All tree-processing phases implement the Visitor pattern via BaseASTVisitor<S, E>. Each AST node has an accept(BaseASTVisitor) method that calls back the corresponding visitNode overload on the visitor, enabling double-dispatch without casts.

See the individual phase pages for deeper details: