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package com.craftinginterpreters.lox;
import java.util.HashMap;
import java.util.Map;
class Environment {
final Environment enclosing;
private final Map<String, Object> values = new HashMap<>();
Environment() {
enclosing = null;
}
Environment(Environment enclosing) {
this.enclosing = enclosing;
}
Object get(Token name) {
if (values.containsKey(name.lexeme)) {
return values.get(name.lexeme);
}
if (enclosing != null)
return enclosing.get(name);
throw new RuntimeError(name, "Undefined variable '" + name.lexeme + "'.");
}
void assign(Token name, Object value) {
if (values.containsKey(name.lexeme)) {
values.put(name.lexeme, value);
return;
}
if (enclosing != null) {
enclosing.assign(name, value);
return;
}
throw new RuntimeError(name, "Undefined variable '" + name.lexeme + "'.");
}
void define(String name, Object value) {
values.put(name, value);
}
Environment ancestor(int distance) {
Environment environment = this;
for (int i = 0; i < distance; i++) {
environment = environment.enclosing;
}
return environment;
}
Object getAt(int distance, String name) {
return ancestor(distance).values.get(name);
}
void assignAt(int distance, Token name, Object value) {
ancestor(distance).values.put(name.lexeme, value);
}
}
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