diff options
Diffstat (limited to 'src/com/craftinginterpreters/lox/Resolver.java')
-rw-r--r-- | src/com/craftinginterpreters/lox/Resolver.java | 210 |
1 files changed, 210 insertions, 0 deletions
diff --git a/src/com/craftinginterpreters/lox/Resolver.java b/src/com/craftinginterpreters/lox/Resolver.java new file mode 100644 index 0000000..2a870ab --- /dev/null +++ b/src/com/craftinginterpreters/lox/Resolver.java @@ -0,0 +1,210 @@ +package com.craftinginterpreters.lox; + +import java.util.HashMap; +import java.util.List; +import java.util.Map; +import java.util.Stack; + +class Resolver implements Expr.Visitor<Void>, Stmt.Visitor<Void> { + private final Interpreter interpreter; + private final Stack<Map<String, Boolean>> scopes = new Stack<>(); + private FunctionType currentFunction = FunctionType.NONE; + + Resolver(Interpreter interpreter) { + this.interpreter = interpreter; + } + + private enum FunctionType { + NONE, FUNCTION + } + + public void resolve(List<Stmt> statements) { + for (Stmt statement : statements) { + resolve(statement); + } + } + + @Override + public Void visitBlockStmt(Stmt.Block stmt) { + beginScope(); + resolve(stmt.statements); + endScope(); + return null; + } + + @Override + public Void visitExpressionStmt(Stmt.Expression stmt) { + resolve(stmt.expression); + return null; + } + + @Override + public Void visitFunctionStmt(Stmt.Function stmt) { + declare(stmt.name); + define(stmt.name); + + resolveFunction(stmt, FunctionType.FUNCTION); + return null; + } + + @Override + public Void visitIfStmt(Stmt.If stmt) { + resolve(stmt.condition); + resolve(stmt.thenBranch); + if (stmt.elseBranch != null) + resolve(stmt.elseBranch); + return null; + } + + @Override + public Void visitPrintStmt(Stmt.Print stmt) { + resolve(stmt.expression); + return null; + } + + @Override + public Void visitReturnStmt(Stmt.Return stmt) { + if (currentFunction == FunctionType.NONE) { + Lox.error(stmt.keyword, "Can't return from top-level code."); + } + + if (stmt.value != null) { + resolve(stmt.value); + } + + return null; + } + + @Override + public Void visitVarStmt(Stmt.Var stmt) { + declare(stmt.name); + if (stmt.initializer != null) { + resolve(stmt.initializer); + } + define(stmt.name); + return null; + } + + @Override + public Void visitWhileStmt(Stmt.While stmt) { + resolve(stmt.condition); + resolve(stmt.body); + return null; + } + + @Override + public Void visitAssignExpr(Expr.Assign expr) { + resolve(expr.value); + resolveLocal(expr, expr.name); + return null; + } + + @Override + public Void visitBinaryExpr(Expr.Binary expr) { + resolve(expr.left); + resolve(expr.right); + return null; + } + + @Override + public Void visitCallExpr(Expr.Call expr) { + resolve(expr.callee); + + for (Expr argument : expr.arguments) { + resolve(argument); + } + + return null; + } + + @Override + public Void visitGroupingExpr(Expr.Grouping expr) { + resolve(expr.expression); + return null; + } + + @Override + public Void visitLiteralExpr(Expr.Literal expr) { + return null; + } + + @Override + public Void visitLogicalExpr(Expr.Logical expr) { + resolve(expr.left); + resolve(expr.right); + return null; + } + + @Override + public Void visitUnaryExpr(Expr.Unary expr) { + resolve(expr.right); + return null; + } + + @Override + public Void visitVariableExpr(Expr.Variable expr) { + if (!scopes.isEmpty() && scopes.peek().get(expr.name.lexeme) == Boolean.FALSE) { + Lox.error(expr.name, "Can't read local variable in its own initializer."); + } + + resolveLocal(expr, expr.name); + return null; + } + + private void resolve(Stmt stmt) { + stmt.accept(this); + } + + private void resolve(Expr expr) { + expr.accept(this); + } + + private void resolveFunction(Stmt.Function function, FunctionType type) { + FunctionType enclosingFunction = currentFunction; + currentFunction = type; + + beginScope(); + for (Token param : function.params) { + declare(param); + define(param); + } + resolve(function.body); + endScope(); + currentFunction = enclosingFunction; + } + + private void beginScope() { + scopes.push(new HashMap<String, Boolean>()); + } + + private void endScope() { + scopes.pop(); + + } + + private void declare(Token name) { + if (scopes.isEmpty()) + return; + + Map<String, Boolean> scope = scopes.peek(); + if (scope.containsKey(name.lexeme)) { + Lox.error(name, "Already variable with this name in this scope."); + } + scope.put(name.lexeme, false); + } + + private void define(Token name) { + if (scopes.isEmpty()) + return; + scopes.peek().put(name.lexeme, true); + } + + private void resolveLocal(Expr expr, Token name) { + for (int i = scopes.size() - 1; i >= 0; i--) { + if (scopes.get(i).containsKey(name.lexeme)) { + interpreter.resolve(expr, scopes.size() - 1 - i); + return; + } + } + } +} |