/* Autor: Amaro R. Silva, Prof. IST- Mar. 1994
* ponha libML.a e mathlink.h em locais acessiveis ao compilador e linker
* uso geral em unix: 
*
* mprep templatefile.tm -o templatefile.tm.c  
* gcc -o exefile  codefile.c  templatefile.tm.c  -lML  -lm
*
*  (veja as notas de ajuda para compilar noutros sistemas)
*
* Use Line[Partition[Arrow[...],2]] no Mathematica para desenhar o resultado
*/

#include "mathlink.h"
#include "mdefs.h"
#include <math.h>
#include <stdio.h>
#include <stdlib.h>

/*==========================Global Vars============================*/

	double  *arrowlist,x,y,L,s;
	void rotatetip();
	
arrow(double *data,int n,double h)
{
	int 			i,j,k=0;

	s=h;	
	MLFlush(stdlink);	
	MLClearError(stdlink);
	k=0;
	while(k<=n){arrowlist[k]=data[k];k++;}
	L=sqrt(data[0]*data[0]+data[1]*data[1]);

	rotatetip(arrowlist);

	MLPutRealList(stdlink,arrowlist,n+10);
	MLEndPacket(stdlink);
	MLFlush(stdlink);
	MLClearError(stdlink);
	return;
	}

/*========================================================================*/
void					rotatetip(double *data)
/*========================================================================*/
{
		
		double  	tip[]={-2.,0.,-1., 1., 3., -1.,-3.,-1.,1.,1.};
		int i;
		x=data[0];
		y=data[1];

		for(i=0;i<10;i+=2){
				arrowlist[2+i]=arrowlist[i]+s*(tip[i]*x-tip[i+1]*y)/(L+.1);
				arrowlist[2+i+1]=arrowlist[i+1]+s*(tip[i]*y+tip[i+1]*x)/(L+.1);
			}

	return ;
}



int   main(int argc, char *argv[])
{

arrowlist=(double *)malloc(sizeof(double)*100000);

MLMain(argc, argv);

free(arrowlist);

return ; 
}