/*
*
* 访问while表达式
*/
public override object VisitWhileStatement([NotNull] CMMParser.WhileStatementContext context)
{
/*
* 如果expression的操作结果是false，就在栈中压入0，否则压入1.
*
*/
int curSize = curLocalVariablesTableLength;
int idx = codes.Count;
IntermediateCode code0 = new IntermediateCode(0, InstructionType.push, context.Start.Line);
codes.Add(code0);
// 查看expression的结果
Visit(context.expression());
// 比较expression的结果和1的关系
// code1的目的地址等待后续回填。因为如果与0相等，说明是false，则需要跳转到codeBlock后面的位置。
IntermediateCode code1 = new IntermediateCode(InstructionType.je, context.expression().Start.Line);
codes.Add(code1);
// addr0是codeBlock的开始地址。
int addr0 = codes.Count;
Visit(context.codeBlock());
IntermediateCode code2 = new IntermediateCode(0, InstructionType.j, context.codeBlock().Stop.Line);
codes.Add(code2);
int addr1 = codes.Count;
// 这个时候回填地址，如果刚才的条件判断不满足，那么目的地址是codeBlock结束的地址addr1
code1.setOperant(addr1);
code2.setOperant(idx);
codes.Add(new IntermediateCode(curSize, InstructionType.delv, context.codeBlock().Stop.Line));
curLocalVariablesTableLength = curSize;
removeVariableBiggerThanK(curSize);
return(null);
}
/// <summary>
/// Visit a parse tree produced by <see cref="CMMParser.whileStatement"/>.
/// <para>
/// The default implementation returns the result of calling <see cref="AbstractParseTreeVisitor{Result}.VisitChildren(IRuleNode)"/>
/// on <paramref name="context"/>.
/// </para>
/// </summary>
/// <param name="context">The parse tree.</param>
/// <return>The visitor result.</return>
public virtual Result VisitWhileStatement([NotNull] CMMParser.WhileStatementContext context)
{
return(VisitChildren(context));
}
/// <summary>
/// Exit a parse tree produced by <see cref="CMMParser.whileStatement"/>.
/// <para>The default implementation does nothing.</para>
/// </summary>
/// <param name="context">The parse tree.</param>
public virtual void ExitWhileStatement([NotNull] CMMParser.WhileStatementContext context)
{
}