size(8cm,0);
import geometry;

show(currentcoordsys);

pair a=(0,0.5), b=(1,0.5);
point A=a, B=b;

dot("$A$",A);
dot("$B$",B);

/* View the definition of coordsys cartesiansystem(pair,pair,pair) */
currentcoordsys=cartesiansystem((0.5,0.5), i=(0.7,0.7), j=(-0.7,0.7));
show("$O'$", "$\vec{u'}$", "$\vec{v'}$", currentcoordsys, xpen=invisible);

point Ap=a;
/* View the definition of point point(coordsys,explicit point,real) */
point Bp=point(currentcoordsys,B); // same as 'point Bp=b;'

dot("$A'$",Ap);
dot("$B'$",Bp);
dot("$M$",(Ap+Bp)/2);

draw(Ap--Bp);

/* View the definition of point locate(pair) */
draw(locate((0,0))--Bp,blue);

/* View the definition of pair locate(point) */
draw((0,0)--locate(Bp),0.8*green);