@Override
public Environment compute(Environment e, IPersistentMap bindings) {
try {
Var v=RT.var(sym.getNamespace(),sym.getName());
if (v!=null) return e.withResult(v.deref());
} catch (Throwable t) {
String err="Error trying to lookp var "+sym+" ";
err+=" with Environment "+e.toString();
throw new KissException(err,t);
}