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semantic.cpp in func_draw.rar

			
#include "semantics.h"

extern double 
	Parameter,
	Origin_x,Origin_y,
	Scale_x,Scale_y,
	Rot_angle;

double GetExprValue(struct ExprNode *root);
void DrawPixel(unsigned long x,unsigned long y);
void DrawLoop(double Start,double End,double Step,struct ExprNode *HorPtr,struct ExprNode *VerPtr);
void DelExprTree(struct ExprNode *root);
static void Errmsg(char *string);
static void CalcCoord(struct ExprNode *Hor_Exp,struct ExprNode *Ver_Exp, 
					  double &Hor_x, double &Ver_y);
void Errmsg(char *string)
{
	exit(1);
}
static void CalcCoord(struct ExprNode *Hor_Exp,struct ExprNode *Ver_Exp,double &Hor_x, double &Ver_y)
{
	double HorCord,VerCord,Hor_tmp;
	HorCord=GetExprValue(Hor_Exp);
	VerCord=GetExprValue(Ver_Exp);
	HorCord *=Scale_x;
	VerCord *=Scale_y;
	Hor_tmp=HorCord *cos(Rot_angle)+VerCord *sin(Rot_angle);
	VerCord=VerCord *cos(Rot_angle)-HorCord*sin(Rot_angle);
	HorCord=Hor_tmp;
	HorCord+=Origin_x;
	VerCord+=Origin_y;
	Hor_x=HorCord;
	Ver_y=VerCord;
}
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);
	}
}
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			

			...
			...
			... to be continued.

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