// import settings;
import graph;

// pdfviewer="evince";
// psviewer="evince";

// returns a pair representation of a relative number of the equivalent class
pair pairRepresentation(int n){
	if(n>0){
		return(n,0);
	}else{
		return(0,-n);
	}
}

string nullString(real r){
	return "";
}

void drawCoordinates(pair point, align align=NoAlign){
	label("$("+string(point.x)+","+string(point.y)+")$",point,align);
}

unitsize(50,50);

int num = 10;
int i;

for (i=-1*num ; i<=num ; ++i) {
	pair point = pairRepresentation(i) ;
	dot(point,red);

	// equivalence classes labelled with usual names, in blue
	label("$\mathbf{"+string(i)+"}$",point,5SW,fontsize(17)+blue);

	int j;
	for(j=abs(i);j<num;++j) {
		drawCoordinates(point,E);
		pair nextpoint = point + (1,1);

		draw(point -- nextpoint,blue+Dotted+linewidth(2));
		dot(point,red+linewidth(5));

		point=nextpoint;
	}
	dot(point,red);
	draw(point -- point+(0.5,0.5),blue+Dotted+linewidth(2));
	dot(point,red+linewidth(5));
	drawCoordinates(point,E);
}

// axes 

real decay=-0.2;

ticks tick=RightTicks(N=0,n=1,end=false,nullString);
xaxis("$n_1$",YEquals(decay),decay,num+1.0,tick,Arrow);
yaxis("$n_2$",XEquals(decay),decay,num+1.0,LeftTicks(N=0,n=1,end=false,nullString),Arrow);