semantic.cpp

该文件主要是一个编译原理函数语言绘图器

#include "semantic.h"

extern double  
	Parameter,           //参数T的存储空间
	Origin_x, Origin_y,  //横、纵平移距离
	Scale_x,   Scale_y,  //横、纵比例因子
	Rot_angle;            //旋转角度

double GetExprValue(struct ExprNode *root); //获得表达式的值
void DrawPixel(unsigned long x, unsigned long y); //绘制一个点
void DrawLoop(double Start,                       //绘制图形
							double End,
							double Step,
							struct ExprNode * HorPtr,
							struct ExprNode * VerPtr );
void DelExprTree(struct ExprNode * root);   //删除一棵语法树

static void Errmsg(char *string);                //出错处理
static void CalcCoord(struct ExprNode * Hor_Exp,  //计算点的坐标
                        struct ExprNode * Ver_Exp,
                        double &Hor_x,
                        double &Very);
//------出错处理
void Errmsg (char *string) { exit(1); }

//-----计算被绘制点的坐标
static void CalcCoord(struct ExprNode * Hor_Exp,
                        struct ExprNode * Ver_Exp,
                        double &Hor_x,
                        double &Ver_y){   
	double HorCord, VerCord, Hor_tmp;
	//计算表达式的值，得到点的原始坐标
	HorCord = GetExprValue(Hor_Exp);
	VerCord = GetExprValue(Ver_Exp);
	//进行比例变换
	HorCord *= Scale_x;
	VerCord *= Scale_y;
	//进行旋转变换
	Hor_tmp = HorCord * cos(Rot_angle) + VerCord * sin(Rot_angle);
	VerCord = VerCord * cos(Rot_angle) - HorCord * sin(Rot_angle);
	HorCord = Hor_tmp;
	//进行平移变换
	HorCord += Origin_x ;
	VerCord += Origin_y ;
	//返回变换后点的坐标	
	Hor_x = HorCord;
	Ver_y = VerCord;	
}

//-------循环绘制点坐标
void DrawLoop(double Start,
                 double End,
                 double Step,
                 struct ExprNode * HorPtr,
                 struct ExprNode * VerPtr ){  
	extern double Parameter;
	double x, y;
	for(Parameter = Start; Parameter <= End; Parameter += Step) {  
			 CalcCoord(HorPtr, VerPtr, x, y);
			 DrawPixel((unsigned long)x, (unsigned long)y);
	}
}

//------------计算表达式的值
double GetExprValue(struct ExprNode *root){
	if (root == NULL) return 0.0;
	switch (root->OpCode)  {   
		case PLUS :
			return GetExprValue(root->Content.CaseOperator.Left) +
				GetExprValue(root->Content.CaseOperator.Right);
		case MINUS:
			return GetExprValue(root->Content.CaseOperator.Left) -
				GetExprValue(root->Content.CaseOperator.Right);
		case MUL :
			return GetExprValue(root->Content.CaseOperator.Left) *
				GetExprValue(root->Content.CaseOperator.Right);
		case DIV :
			return GetExprValue(root->Content.CaseOperator.Left) /
				GetExprValue(root->Content.CaseOperator.Right);
		case POWER:
			return pow(GetExprValue(root->Content.CaseOperator.Left ),
				GetExprValue(root->Content.CaseOperator.Right) );
		case FUNC  :
			return (* root->Content.CaseFunc.MathFuncPtr)
							 (GetExprValue(root->Content.CaseFunc.Child) );
		case CONST_ID:
			return root->Content.CaseConst;
		case T :
			return * (root->Content.CaseParmPtr);
		default :
			return 0.0;
	}
}
// --------- 删除一棵语法树
void DelExprTree(struct ExprNode *root)
{ 
  if (root == NULL) return;
	switch (root->OpCode)  {   
		case PLUS :              // 两个孩子的内部结点
		case MINUS:
		case MUL  :
		case DIV  :
		case POWER:
			DelExprTree (root->Content.CaseOperator.Left);
			DelExprTree (root->Content.CaseOperator.Right);
			break;
		case FUNC  :             // 一个孩子的内部节点
			DelExprTree (root->Content.CaseFunc.Child);
			break;
		default  :             // 叶子节点
			break;
	}
	delete(root);                  // 删除节点
}

// ----------绘制一个点
void DrawPixel(unsigned long x,unsigned long y){
	SetPixel(hDC,x,y,black);
}