On Wed, May 25, 2016 at 03:22:01PM +0100, Rainer Weikusat wrote: > > The LISP "alist" implementation is, as we noted earlier, an > example of the "deep access" approach". The "alist" contains > pointers to previous values of all bound variables together with > the variable names. The name of the variable appears on the left > side of a pair, and the value of the variable on the right side. > > [ftp://publications.ai.mit.edu/ai-publications/pdf/AIM-199.pdf, > p. 5] > > [...] when one transmits a functional argument f which is to be > evaluated in its binding environment, then one uses FUNCTION(f) > instead of QUOTE(f). [...] The result of FUNCTION will be a > structure which not only contains a reference to the function f > but also contains a pointer to the binding environment. Thus at > the FUNARG's activation time we will be able to use the pointer > to restore the environment to the proper place. > > [...] > > In the "alist implementation, this process is even easier, > because the save pointer is made the current "alist", and we are > done because the values of free variables will be obtained from > the "alist" which contains the binding environment. > [p. 7, 8]
If you're using alists, lexical scoping is more efficient than dynamic scoping, because you won't be searching lond association lists all the time. -- hendrik _______________________________________________ Dng mailing list Dng@lists.dyne.org https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng
