global variables

This commit is contained in:
David 2021-09-19 14:13:47 -04:00
parent d6cbc63c18
commit b1cd274a39
8 changed files with 108 additions and 19 deletions

View File

@ -28,6 +28,11 @@ class ASTPrinter implements Expr.Visitor<String> {
return parenthesize(expr.operator.lexeme, expr.right);
}
@Override
public String visitVariableExpr(Expr.Variable expr) {
return expr.name.toString();
}
private String parenthesize(String name, Expr... exprs) {
StringBuilder builder = new StringBuilder();

19
src/lox/Environment.java Normal file
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@ -0,0 +1,19 @@
package lox;
import java.util.HashMap;
import java.util.Map;
class Environment {
private final Map<String, Object> values = new HashMap<>();
void define(String name, Object value) {
values.put(name, value);
}
Object get(Token name) {
if (values.containsKey(name.lexeme)) {
return values.get(name.lexeme);
}
throw new RuntimeError(name, "Undefined variable '" + name.lexeme + "'.");
}
}

View File

@ -1,13 +1,12 @@
package lox;
import java.util.List;
abstract class Expr {
interface Visitor<R> {
R visitBinaryExpr(Binary expr);
R visitGroupingExpr(Grouping expr);
R visitLiteralExpr(Literal expr);
R visitUnaryExpr(Unary expr);
R visitVariableExpr(Variable expr);
}
static class Binary extends Expr {
@ -68,5 +67,18 @@ abstract class Expr {
final Expr right;
}
static class Variable extends Expr {
Variable(Token name) {
this.name = name;
}
@Override
<R> R accept(Visitor<R> visitor) {
return visitor.visitVariableExpr(this);
}
final Token name;
}
abstract <R> R accept(Visitor<R> visitor);
}

View File

@ -3,6 +3,8 @@ package lox;
import java.util.List;
class Interpreter implements Expr.Visitor<Object>, Stmt.Visitor<Void> {
private Environment environment = new Environment();
void interpret(List<Stmt> statements) {
try {
for (Stmt statement : statements) {
@ -82,6 +84,11 @@ class Interpreter implements Expr.Visitor<Object>, Stmt.Visitor<Void> {
return null;
}
@Override
public Object visitVariableExpr(Expr.Variable expr) {
return environment.get(expr.name);
}
@Override
public Void visitExpressionStmt(Stmt.Expression stmt) {
evaluate(stmt.expression);
@ -95,6 +102,16 @@ class Interpreter implements Expr.Visitor<Object>, Stmt.Visitor<Void> {
return null;
}
@Override
public Void visitVarStmt(Stmt.Var stmt) {
Object value = null;
if (stmt.initializer != null) {
value = evaluate(stmt.initializer);
}
environment.define(stmt.name.lexeme, value);
return null;
}
private void checkNumberOperand(Token operator, Object operand) {
if (operand instanceof Double) {
return;

View File

@ -18,11 +18,34 @@ class Parser {
List<Stmt> parse() {
List<Stmt> statements = new ArrayList<>();
while (!isAtEnd()) {
statements.add(statement());
statements.add(declaration());
}
return statements;
}
private Stmt declaration() {
try {
if (match(VAR)) {
return varDeclaration();
}
return statement();
} catch (ParseError error) {
synchronize();
return null;
}
}
private Stmt varDeclaration() {
Token name = consume(IDENTIFIER, "Expect variable name.");
Expr initializer = null;
if (match(EQUAL)) {
initializer = expression();
}
consume(SEMICOLON, "Expect semicolon.");
return new Stmt.Var(name, initializer);
}
private Stmt statement() {
if (match(PRINT)) {
return printStatement();
@ -113,6 +136,9 @@ class Parser {
consume(RIGHT_PAREN, "Expect ')' after expression.");
return new Expr.Grouping(expr);
}
if (match(IDENTIFIER)) {
return new Expr.Variable(previous());
}
throw error(peek(), "Expected expression.");
}
@ -172,14 +198,7 @@ class Parser {
return;
}
switch (peek().type) {
case CLASS:
case FOR:
case FUN:
case IF:
case PRINT:
case RETURN:
case VAR:
case WHILE:
case CLASS, FOR, FUN, IF, PRINT, RETURN, VAR, WHILE:
return;
}
}

View File

@ -106,9 +106,7 @@ class Scanner {
addToken(SLASH);
}
break;
case ' ':
case '\r':
case '\t':
case ' ', '\r', '\t':
break; // skip whitespace
case '\n':
line++;

View File

@ -3,7 +3,7 @@ package lox;
abstract class Stmt {
interface Visitor<R> {
R visitExpressionStmt(Expression stmt);
R visitVarStmt(Var stmt);
R visitPrintStmt(Print stmt);
}
@ -20,6 +20,21 @@ abstract class Stmt {
final Expr expression;
}
static class Var extends Stmt {
Var(Token name, Expr initializer) {
this.name = name;
this.initializer = initializer;
}
@Override
<R> R accept(Visitor<R> visitor) {
return visitor.visitVarStmt(this);
}
final Token name;
final Expr initializer;
}
static class Print extends Stmt {
Print(Expr expression) {
this.expression = expression;

View File

@ -20,12 +20,16 @@ public class GenerateAST {
"Binary : Expr left, Token operator, Expr right",
"Grouping : Expr expression",
"Literal : Object value",
"Unary : Token operator, Expr right"));
"Unary : Token operator, Expr right",
"Variable : Token name"));
defineAST(
outputDir,
"Stmt",
Arrays.asList("Expression : Expr expression", "Print : Expr expression"));
Arrays.asList(
"Expression : Expr expression",
"Var : Token name, Expr initializer",
"Print : Expr expression"));
}
private static void defineAST(String outputDir, String baseName, List<String> types)
@ -35,8 +39,8 @@ public class GenerateAST {
writer.println("package lox;");
writer.println();
writer.println("import java.util.List;");
writer.println();
// writer.println("import java.util.List;");
// writer.println();
writer.println("abstract class " + baseName + " {");
defineVisitor(writer, baseName, types);