[plt-scheme] MrEd: Structure problem

Hi,
I'm making a project using MrEd which finished should allow drawing euclidian geometry. First, I thought of storing position of all my points in a list in order to be able to move points. But I realized that when I move points, figures which are drawn with them don't change. What I would need is something like pointers in C, so when one coordinates changes, all figures which use them, will change too. Does something similar exists in scheme?
 
 		
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