/*
* 处理赋值操作，
* 前提：leftValue将待赋值的变量在局部变更量表中的索引已经压入栈中，expression处理的结果已经压入操作栈中
*/
public override object VisitAssignment([NotNull] CMMParser.AssignmentContext context)
{
Visit(context.leftValue());
// tmp是一个虚拟的变量，用于 存储leftVal的索引 在局部变量表的位置
int tmp = curLocalVariablesTableLength;
// 把leftVal的值放到局部变更量表Count位置上
IntermediateCode code0 = new IntermediateCode(tmp, InstructionType.pop, context.leftValue().Start.Line);
codes.Add(code0);
// 把Expression的值压入栈中
Visit(context.expression());
//将Experession的值放入Count中
IntermediateCode code1 = new IntermediateCode("(" + tmp + ")", InstructionType.pop, context.expression().Start.Line);
// 这个过程中，局部变量表并没有增加新的元素，所以curLocalVariable并没有Add操作
codes.Add(code1);
// 局部变量表里面，1号位置的值是0
return(null);
}
/// <summary>
/// Visit a parse tree produced by <see cref="CMMParser.assignment"/>.
/// <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 VisitAssignment([NotNull] CMMParser.AssignmentContext context)
{
return(VisitChildren(context));
}
/// <summary>
/// Exit a parse tree produced by <see cref="CMMParser.assignment"/>.
/// <para>The default implementation does nothing.</para>
/// </summary>
/// <param name="context">The parse tree.</param>
public virtual void ExitAssignment([NotNull] CMMParser.AssignmentContext context)
{
}
