/*
Title:   /*
Title:   Vectors.h
Author:  Xiaoyang Yu
Revised: 22-NOV-2002

Module Interface Specification:
INTERFACE Vectors;
TYPE vector;
CONST zero: vector;
PROCEDURE getvec(x,y: float): vector;
PROCEDURE xval(v: vector): float;
PROCEDURE yval(v: vector): float;
PROCEDURE add(u,v: vector): vector;
PROCEDURE mul(r: float; v: vector): vector;
END Vectors.
*/

/* macro definition */
#define zero getvec(0,0)

/* type definition */
typedef struct rec *vector;

/* return the pointer of vector ( x, y ) */
extern vector getvec(float x, float y);

/* return xval of vector v */
extern float xval(vector v);

/* return yval of vector v */
extern float yval(vector v);

/* add vector u and vector v */
extern vector add(vector u, vector v);

/* multiple r and vector v */
extern vector mul(float r, vector v);

/* show linklist:test only,delete later */
extern void showlist();

/* the end of vectors.h */