LoopGotoStatement.java

package calculator.interpreter.ast.logic;

import calculator.interpreter.Cell;
import calculator.interpreter.Environment;
import calculator.interpreter.EvalException;
import calculator.interpreter.Variable;
import calculator.interpreter.ast.Statement;

/**
 * The loop goto statement
 */
public abstract class LoopGotoStatement extends Statement {
  /** the label of loop (may be null) */
  public String label;

  @Override
  public Environment eval(Environment env, Cell result) {
    Variable var = env.find(WhileStatement.tokenName(label));
    if (var == null) {
      throw new EvalException(this, "The break and continue statements "
          + "must happen only in the lexical scope of the loop.");
    }
    if (var.value == null) {
      throw new EvalException(this, "The break and continue statements "
          + "must happen only while loop is acitve.");
    }
    throw new WhileStatement.LoopGotoException(var.value, isBreak());
  }

  /**
   * @return true if it is break statement, false if continue
   */
  protected abstract boolean isBreak();
}