On Fri, Jan 08, 2016 at 03:18:38PM -0500, Doug McIlroy wrote:
exps = 1 + integral exps
Can you explain why the first line won't work for lazy lists in a strict language? It seems perfectly fine to me.
Tom If I understand well the issue, simply because at the RHS exps is not a
Le 08/01/2016 21:33, Tom Ellis a écrit : thunk, it is evaluated, which breaks down the co-recursivity of the definition, even if the operators are delayed. In a strict language you would have to use a kind of macros to make it work. Good, old days... I believe I wrote a paper on lazy power series already in 1996 (but Douglas McI. hasn't read it). (Theoretical Computer Science 187, pp. 203–219, (1997).) I still have a copy: https://karczmarczuk.users.greyc.fr/Transport/power.pdf and I tried hard to do some Computer Algebra with that, trying to implement by force some lazy algorithms in a strict CA language MuPAD (similar to Maple, with strong OO structure). It was clumsy and almost nobody was convinced, when I presented this in Paderborn, the home of MuPAD. https://karczmarczuk.users.greyc.fr/Transport/paslid.pdf Then MuPad quit the free software world, got attached to MathWorks, and I simply forgot this experiment. I tried to convince some students to continue it using Mathematica (Hold, HoldRest, etc. permit to construct delayed lists; in general, a rewriting system seems better adapted to such kind of implementation, than purely procedural languages), but the results were ugly, and my dear students asked me to give them some other project... Jerzy Karczmarczuk