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  • Parsing Lisp S-Expressions with known schema in C#

    - by Drew Noakes
    I'm working with a service that provides data as a Lisp-like S-Expression string. This data is arriving thick and fast, and I want to churn through it as quickly as possible, ideally directly on the byte stream (it's only single-byte characters) without any backtracking. These strings can be quite lengthy and I don't want the GC churn of allocating a string for the whole message. My current implementation uses CoCo/R with a grammar, but it has a few problems. Due to the backtracking, it assigns the whole stream to a string. It's also a bit fiddly for users of my code to change if they have to. I'd rather have a pure C# solution. CoCo/R also does not allow for the reuse of parser/scanner objects, so I have to recreate them for each message. Conceptually the data stream can be thought of as a sequence of S-Expressions: (item 1 apple)(item 2 banana)(item 3 chainsaw) Parsing this sequence would create three objects. The type of each object can be determined by the first value in the list, in the above case "item". The schema/grammar of the incoming stream is well known. Before I start coding I'd like to know if there are libraries out there that do this already. I'm sure I'm not the first person to have this problem.

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  • function using cl-who:with-html-output ignoring parameter

    - by shanked
    I'm not sure whether this is an issue with my use of cl-who (specifically with-html-output-to-string and with-html-output) or an issue with my understanding of Common Lisp (as this is my first project using Lisp). I created a function to create form fields: (defun form-field (type name label) (cl-who:with-html-output (*standard-output* nil) (:div :class "field" (:label :for name label) (:input :type type :name name)))) When using this function, ie: (form-field "text" "username" "Username") the parameter label seems to be ignored... the HTML output is: <div class="field"><label for="username"></label> <input type="text" name="username"/></div> instead of the expected output: <div class="field"><label for="username">Username</label> <input type="text" name="username"/></div> If I modify the function and add a print statement: (defun form-field (type name label) (cl-who:with-html-output (*standard-output* nil) (print label) (:div :class "field" (:label :for name label) (:input :type type :name name)))) The "Username" string is successfully output (but still ignored in the HTML)... any ideas what might cause this? Keep in mind, I'm calling this function within a cl-who:with-html-output-to-string for use with hunchentoot.

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  • Performance difference between functions and pattern matching in Mathematica

    - by Samsdram
    So Mathematica is different from other dialects of lisp because it blurs the lines between functions and macros. In Mathematica if a user wanted to write a mathematical function they would likely use pattern matching like f[x_]:= x*x instead of f=Function[{x},x*x] though both would return the same result when called with f[x]. My understanding is that the first approach is something equivalent to a lisp macro and in my experience is favored because of the more concise syntax. So I have two questions, is there a performance difference between executing functions versus the pattern matching/macro approach? Though part of me wouldn't be surprised if functions were actually transformed into some version of macros to allow features like Listable to be implemented. The reason I care about this question is because of the recent set of questions (1) (2) about trying to catch Mathematica errors in large programs. If most of the computations were defined in terms of Functions, it seems to me that keeping track of the order of evaluation and where the error originated would be easier than trying to catch the error after the input has been rewritten by the successive application of macros/patterns.

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  • Vector addition of lists

    - by ntimes
    If I had a N lists each of length M, how could I write a nice clean function to return a single list of length M, where each element is the sum of the corresponding elements in the N lists? (starting to learn lisp - go easy!)

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  • How can you make an emacs macro wait for cscope query results?

    - by Sudhanshu
    I am trying to write a macro which calls cscope-find-functions-calling-this-function on each and every tag in a file displayed in the *Tags List* buffer (created by list-tags command). This should create a buffer which contains list of all functions calling a set of functions defined in a certain file. This is the sequence of keystrokes: 1. <f11> ;; cscope-find-functions-calling-this-function 2. RET ;; newline [shows results of cscope in a split window] 3. C-x C-p ;; mark-page 4. C-x C-x ;; icicle-exchange-point-and-mark 5. <up> ;; previous-line 6. <end> ;; end-of-line [region to copy has been marked] 7. <f7> ;; append-results-to-buffer 8. C-x ESC O ;; [move back to split window on the right] 9. C-x b ;; icicle-buffer [Switch back to *Tags List* buffer] 10. *Tags ;; self-insert-command * 5 11. SPC ;; self-insert-command 12. List* ;; self-insert-command * 5 13. RET ;; newline 14 . <down> ;; next-line [Position point on next tag in the list] Problem: I get no results in the buffer, and I found out that's because Step 3-7 execute even before cscope prints the results of query made on Steps 1-2. I can insert a pause in the macro by using C-x q, but I'd rather like the macro to wait after Step 2, until cscope has returned with the results and only then continue further. I suspect this is not possible through a macro, maybe a LISP function... I'm not a lisp expert myself. Can someone please help? Thanks! Details: I have Icicles installed so by default I get word at point in current buffer as input in minibuffer. F11 is bound to cscope-find-functions-calling-this-function windmove is installed and C-x (C-x ESC o - as shown below) takes you to the right window. F7 is bound to append-results-to-buffer which is defined as: (defun append-results-to-buffer () (interactive) (append-to-buffer (get-buffer-create "c1") (point) (mark))) This function just appends the currently marked region to a buffer named "c1".

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  • Rule of thumb for capitalizing the letters in a programming language

    - by William
    I was wondering if anyone knew why some programming languages that I see most frequently spelled in all caps (like an acronym), are also commonly written in lower case. FORTRAN, LISP, and COBOL come to mind but I'm sure there are many more. Perhaps there isn't any reason for this, but I'm curious to know if any of these changes are due to standards or decisions by their respective communities. Or are people just getting too lazy to hit the caps lock key? (I know I am)

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  • scheme2lisp::define function and pass it as parameter

    - by Stas
    Hi! Im need translate some code from scheme to common lisp. Now I have something like this (defun sum (term a next b) (if (> a b) 0 (+ (term a) (sum term (next a) b)))) (defun sum-int (a b) (defun (ident x) x ) (sum ident a 1+ b)) But it doesn't interprete with out errors. * - DEFUN: the name of a function must be a symbol, not (IDENT X) Help me plese. Thanks

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  • emacs: how do I use edebug on code that is defined in a macro?

    - by Cheeso
    I don't even know the proper terminology for this lisp syntax, so I don't know if the words I'm using to ask the question, make sense. But the question makes sense, I'm sure. So let me just show you. cc-mode (cc-fonts.el) has things called "matchers" which are bits of code that run to decide how to fontify a region of code. That sounds simple enough, but the matcher code is in a form I don't completely understand, with babckticks and comma-atsign and just comma and so on, and furthermore it is embedded in a c-lang-defcost, which itself is a macro. And I want to run edebug on that code. Look: (c-lang-defconst c-basic-matchers-after "Font lock matchers for various things that should be fontified after generic casts and declarations are fontified. Used on level 2 and higher." t `(;; Fontify the identifiers inside enum lists. (The enum type ;; name is handled by `c-simple-decl-matchers' or ;; `c-complex-decl-matchers' below. ,@(when (c-lang-const c-brace-id-list-kwds) `((,(c-make-font-lock-search-function (concat "\\<\\(" (c-make-keywords-re nil (c-lang-const c-brace-id-list-kwds)) "\\)\\>" ;; Disallow various common punctuation chars that can't come ;; before the '{' of the enum list, to avoid searching too far. "[^\]\[{}();,/#=]*" "{") '((c-font-lock-declarators limit t nil) (save-match-data (goto-char (match-end 0)) (c-put-char-property (1- (point)) 'c-type 'c-decl-id-start) (c-forward-syntactic-ws)) (goto-char (match-end 0))))))) I am reading up on lisp syntax to figure out what those things are and what to call them, but aside from that, how can I run edebug on the code that follows the comment that reads ;; Fontify the identifiers inside enum lists. ? I know how to run edebug on a defun - just invoke edebug-defun within the function's definition, and off I go. Is there a corresponding thing I need to do to edebug the cc-mode matcher code forms?

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  • Is there a suitable replacement for C++, when I would like to write video processing applications?

    - by Nisanio
    Hi I want to write a video editing software, and the "logical" conclusion is that the language I must to use is C++... But I don't like it (sorry c++ fans) I would like to write it with something cool, like Lisp or Haskell or Erlang... But I don't know if the open source implementation of those languages (I don't have money to buy licenses) let me made a competitive software (in the performance area) What do you think? what do you recommend?

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  • Are incremental Macro definition possible?

    - by Davorak
    I often find the following type of incremental definition useful: (define (foo) (display "bar")) (foo) ;prints bar (define foo (let ((bar foo)) (lambda () (display "foo") (bar)))) (foo) ;prints foobar How do I preform this type of incremental definition with macros? I could not get let-syntax to provide the same functionality. Currently I use plt scheme, but would like to see answers in different lisp implementations as well.

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  • Is incremental Macro definition possible?

    - by Davorak
    I often find the following type of incremental definition useful: (define (foo) (display "bar")) (foo) ;prints bar (define foo (let ((bar foo)) (lambda () (display "foo") (bar)))) (foo) ;prints foobar How do I preform this type of incremental definition with macros? I could not get let-syntax to provide the same functionality. Currently I use plt scheme, but would like to see answers in different lisp implementations as well.

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  • Recenter a named buffer that is not neccessarily the current buffer in emacs Lisp

    - by Yu Shen
    I'd like to recenter a buffer, called "Lense", where I've inserted some text. I wished to make it the current buffer by "(set-buffer "Lense")", then "(recenter 0))". By the following code segments: (save-excursion (set-buffer "Lense") (recenter 0)) However, it seems that the above code would only recenter the buffer which is the current buffer, and "(set-buffer "Lense")" has no effect to make the current buffer to be "Lense". Please help me to figure out the right way to recenter the named buffer "Lense". Thanks, Yu

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  • Wrapping variable width text in emacs lisp

    - by Jonathan Arkell
    I am hacking up a tagging application for emacs. I have got a tag cloud/weighted list successfully displaying on a buffer, but i am running into a snag. I need to be able to properly word-wrap the buffer, but I haven't a clue where to start. The font I am using is a variable width font. On top of that, each tag is going to be in a different size, depending on how many times it shows up on the buffer. Finally, the window that displays the tagcloud could be in a window that is 200 pixels wide, or the full screen width. I really have no idea where to start. I tried longlines mode on the tagcloud buffer, but that didn't work. Source code is at: http://emacswiki.org/cgi-bin/emacs/free-tagging.el

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  • How to check if Emacs is in GUI mode (and execute `tool-bar-mode` only then)?

    - by dehmann
    I have this line in my .emacs file: (tool-bar-mode 0) because I hate the toolbars in my GUI emacs (/Applications/Emacs.app/Contents/MacOS/Emacs). But when I start up my other, text-based emacs in the terminal (/opt/local/bin/emacs) it complains about that command: Symbol's function definition is void: tool-bar-mode How can I add an if condition so that it executes the tool-bar-mode command only when I'm in the GUI emacs? Thanks!

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  • Help With Lisp Code for a Binary Tree

    - by iulia
    I have (setq l2 '(1 (2 b (c 1 b))(a (1 2) d))) ( defun drumuri (l3) ( cond ( (atom l3) ( cons l3 nil)) ( t ( append ( cons ( car l3 ) nil) ( drumuri ( cadr l3)) (cons (car l3)nil) ( drumuri ( caddr l3)) )))) ( drumuri l2) and it gives me: Break 2 [4]> DRUMURI Break 2 [4]> (1 2 B 2 C 1 C B 1 A 1 2 1 NIL A D) but i need: ((1 2 B)(1 2 C 1)(1 2 C B)(1 A 1 2)(1 A D))

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  • Elisp performance on Windows and Linux

    - by JasonFruit
    I have the following dead simple elisp functions; the first removes the fill breaks from the current paragraph, and the second loops through the current document applying the first to each paragraph in turn, in effect removing all single line-breaks from the document. It runs fast on my low-spec Puppy Linux box using emacs 22.3 (10 seconds for 600 pages of Thomas Aquinas), but when I go to a powerful Windows XP machine with emacs 21.3, it takes almost an hour to do the same document. What can I do to make it run as well on the Windows machine with emacs 21.3? (defun remove-line-breaks () "Remove line endings in a paragraph." (interactive) (let ((fill-column 90002000)) (fill-paragraph nil))) : (defun remove-all-line-breaks () "Remove all single line-breaks in a document" (interactive) (while (not (= (point) (buffer-end 1))) (remove-line-breaks) (next-line 1))) Forgive my poor elisp; I'm having great fun learning Lisp and starting to use the power of emacs, but I'm new to it yet.

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  • What does this xkcd code do?

    - by cobbal
    On the xkcd site today, the following appeared as a joke in a <script language="scheme"> tag so what does the following code do / represent? (define (eval exp env) (cond ((self-evaluating? exp) exp) ((variable? exp) (lookup-variable-value exp env)) ((quoted? exp) (text-of-quotation exp)) ((assignment? exp) (eval-assignment exp env)) ((definition? exp) (eval-definition exp env)) ((if? exp) (eval-if exp env)) ((lambda? exp) (make-procedure (lambda-parameters exp) (lambda-body exp) env)) ((begin? exp) (eval-sequence (begin-actions exp) env)) ((cond? exp) (eval (cond->if exp) env)) ((application? exp) (apply (eval (operator exp) env) (list-of-values (operands exp) env))) (else (error "Common Lisp or Netscape Navigator 4.0+ Required" exp))))

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  • Will be self-taught limit me?

    - by Isaiah
    I'm 21 and am pretty efficient in html/css, python, and javascript. I also know my way around lisp languages and enjoy programing in them. My problem is that I'm extremely self-taught and not quite confident that I could land a job programing, but I really need a job soon as I've just become a father. I haven't even created a resume yet because I'm not really sure what to put on it except my lone experience. So I wanted to ask, will being primarily self-taught with some experience on small projects I've done for a few clients limit me too much? I mean I know I need some kind of education so I've enrolled part time in a community college to work on a degree in computer science, but it's years till then. And if it will limit me a lot, what kind of skills would be good to work on to make my chances any better? Thank You

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  • idomatic batch processing of text in emacs?

    - by Stephen
    In python, you might do something like fout = open('out','w') fin = open('in') for line in fin: fout.write(process(line)+"\n") fin.close() fout.close() (I think it would be similar in many other languages as well). In emacs lisp, would you do something like (find-file 'out') (setq fout (current-buffer) (find-file 'in') (setq fin (current-buffer) (while moreLines (setq begin (point)) (move-end-of-line 1) (setq line (buffer-substring-no-properties begin (point)) ;; maybe (print (process line) fout) ;; or (save-excursion (set-buffer fout) (insert (process line))) (setq moreLines (= 0 (forward-line 1)))) (kill-buffer fin) (kill-buffer fout) which I got inspiration (and code) from here. Or should I try something entirely different? And how to remove the "" from the print statement? Thanks!

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  • How are vector patterns used in syntax-rules?

    - by Jay
    Hi, I have been writing Common Lisp macros, so Scheme's R5Rs macros are a bit unnatural to me. I think I got the idea, except that I don't understand how one would use vector patterns in syntax-rules: (define-syntax mac (syntax-rules () ((mac #(a b c d)) (let () (display a) (newline) (display d) (newline))))) (expand '(mac #(1 2 3 4))) ;; Chicken's expand-full extension shows macroexpansion => (let746 () (display747 1) (newline748) (display747 4) (newline748)) I don't see how I'd use a macro that requires its arguments to be written as a vector: (mac #(1 2 3 4)) => 1 4 Is there some kind of technique that uses those patterns? Thank you!

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  • Why exactly is eval evil?

    - by Jay
    I know that Lisp and Scheme programmers usually say that eval should be avoided unless strictly necessary. I´ve seen the same recommendation for several programming languages, but I´ve not yet seen a list of clear arguments against the use of eval. Where can I find an account of the potential problems of using eval? For example, I know the problems of GOTO in procedural programming (makes programs unreadable and hard to maintain, makes security problems hard to find, etc), but I´ve never seen the arguments against eval. Interestingly, the same arguments against GOTO should be valid against continuations, but I see that Shemers, for example, won´t say that continuations are "evil" -- you should just be careful when using them. They´re much more likely to frown upon code using eval than upon code using continuations (as far as I can see -- I could be wrong).

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