lisp

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: The other day (perhaps yesterday) I was quite perplexed about this #+nil read-time conditional found in https://github.com/billstclair/defperson/blob/master/defperson.lisp#L289 . After some deep thinking I came to the conclusion that this is very lispy way of commenting out code. Can someone confirm this? Perhaps my assumptions are completely wrong. Anyway, thanks in advance. 回答1: See CLHS 2.4.8.17 Sharpsign Plus To conditionalize reading expressions from input, Common Lisp uses feature expressions . In this case it has been used to comment

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: Suppose I have a directory A, and subdirectory B. I cd into A and launch lisp. In that lisp process, I would like to launch a Python subprocess where Python sees B as its current working directory. The lisp process needs to have cwd in A, and the python process should have cwd in B. How do I do this in a cross-platform, simple way? I'm looking for a solution that works with CCL and SBCL (probably using 'run-program function), and works for Windows, Linux, and OS X. I looked at the CCL run-program documentation, and I didn't see a way to

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 由 翻译 强力驱动 问题: As a lot of people pointed out in this question , Lisp is mostly used as a learning experience. Nevertheless, it would be great if I could somehow use my Lisp algorithms and combine them with my C# programs. In college my profs never could tell me how to use my Lisp routines in a program (no, not writing a GUI in Lisp, thank you). So how can I? 回答1: Try these .Net implementations of Lisp: IronScheme IronScheme will aim to be a R6RS conforming Scheme implementation based on the Microsoft DLR. L Sharp .NET L Sharp .NET is a powerful

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I think I understand Lisp macros and their role in the compilation phase. But in Python, you can pass a function into another function def f(filename, g): try: fh = open(filename, "rb") g(fh) finally: close(fh) So, we get lazy evaluation here. What can I do with macros and not with functions as first class objects? 回答1: First of all Lisp has first-class functions too, so you could as well ask: "Why do I need macros in Lisp if I already have first-class functions". The answer to that is that first-class functions don't allow you to play with

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: Can someone please explain to me how I search for the occurrences of each word in a sentence, such as "the cat sat on the mat" in Common lisp ? The user has to have inputted this line of text before hand and then the occurrences must be counted from that. Any help on even where to start would help. 回答1: Have a look at split-by-one-space in The Common Lisp Cookbook (defun split-by-one-space (string) "Returns a list of substrings of string divided by ONE space each. Note: Two consecutive spaces will be seen as if there were an empty string

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 由 翻译 强力驱动 问题: While looking through the "Common Lisp Quick Reference" by Bert Burgemeister, I stumbled over tailp . First, I misunderstood the definitions of this function. And I tried: ( tailp '(3 4 5) ' ( 1 2 3 4 5 )) But it returned NIL CLTL2 says, tailp is true iff the first argument is any (nthcdr n list) with existing n . ( nthcdr 2 '(1 2 3 4 5)) ;; (3 4 5) I further tried: ( tailp '(3 4 5) ' ( 1 2 3 4 5 )) ;; NIL - and I would expect : T following the definition above . ( tailp '() ' ( 1 2 3 4 5 )) ;; T ( tailp '5 ' ( 1 2 3 4 . 5 )) ;; T

I read in the book 'On Lisp' that one should avoid excessive use of cons in the body of expanded macros. Why is cons considered to be an inefficient operation? Does Lisp not do structure sharing with the cons cells? You need to understand the jargon first. CONS is a primitive operation to create a fresh cons cell. Consing means allocation of memory on the heap in general, not only cons cells: Consing of numbers, Consing of arrays, Consing of CLOS objects, ... The definition from the 'memory management glossary' says: cons (1) In Lisp, cons is a primitive operation creating a list element (from