gmane.lisp.scheme.plt

regexp-match a full line

Eli Nistal — 2008-10-07T00:29:38

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upgrading installed planet packages

Jose A. Ortega Ruiz — 2008-10-06T21:10:50

Hi, I track PLT using svn, re-building it from source every now and then, which is a rather painless procedure. I usually choose the in-place build/install, linking the binaries to somewhere in my PATH. But everytime the version number of PLT changes, all my downloaded planet packages (living in ~/.plt) are forgotten, because they live in version-specific folders. Is there away of automating their re-installation after an upgrade? I've got the feeling that this is a FAQ, in which case i apologise and will be happy with a link to the relevant discussion or document. Thanks a lot! jao _________________________________________________ For list-related administrative tasks: http://list.cs.brown.edu/mailman/listinfo/plt-scheme

ARM support

Deep — 2008-10-06T19:37:45

I have been using DrScheme to build some game prototypes. I recently preordered a Pandora game console - http://www.openpandora.org to be able to develop games on it. The openpandora is basically an open console and has an ARM cpu and runs linux. I wanted to know if DrScheme has a maintained arm port ? Also - just as an aside have people tried getting DrScheme (or any other scheme) to work on the iPhone (also an ARM device). _________________________________________________ For list-related administrative tasks: http://list.cs.brown.edu/mailman/listinfo/plt-scheme

Need information for create en executable withDrScheme (with windows)

Gilles PHAN — 2008-10-06T16:05:57

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Need information for create en executable with DrScheme (with windows)

Gilles PHAN — 2008-10-06T15:32:55

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Combining two definition into one only

SamuelXiao — 2008-10-05T14:56:13

I am a scheme newbie, could anyone tell me how can i combine this following 2 definition into one? ----------------------------------------------------------------------------------------------------------------------------- (define insert-number (lambda (new-element sorted) (cond ((null? sorted) (list new-element)) ((<= new-element (car sorted)) (cons new-element sorted)) (else (cons (car sorted) (insert-number new-element (cdr sorted))))))) (define insertion-sort-numbers (lambda (numbers) (let helper ((unsorted numbers) ; The remaining unsorted values (sorted '())) ; The sorted values (if (null? unsorted) sorted (helper (cdr unsorted) (insert-number (car unsorted) sorted)))))) _________________________________________________ For list-related administrative tasks: http://list.cs.brown.edu/mailman/listinfo/plt-scheme

PLT Scheme v4.1.1

Eli Barzilay — 2008-10-05T20:14:16

PLT Scheme version 4.1.1 is now available from http://plt-scheme.org/ This is mostly a bug-fix release. Notable changes: * web-server: New servlet development tutorial; quick launching of servlets from DrScheme via the `web-server/insta' language; new form abstraction through formlets. * misc: mzc can "decompile" bytecode files; `#lang' lines wired to the top of DrScheme's definition window; improved searching in DrScheme; some foreign interface extensions. [Note that mirror sites can take a while to catch up with the new downloads.] Feedback Welcome,

tools and practises to derice FFI types from C typedeclarations?

Ernie Smith — 2008-10-05T20:03:11

I'm hoping this isn't the wrong place to be asking this kind of question, if so please redirect me to the right place. I'm trying to access the 'lstat' function within libgc In order to perform some straightforward file attribute tests for a script which hinges on the 'fold-files' function from file.ss. In order to do so I must interface to a stat function and a 'stat' structure declared in include files for that function call. . The foreign interface manual explains well enough how to interact with c structures once you know the primitive types they use. However typical library functions, rather than declare structures using primitive types, tend to use intermediate sub-types, and how these sub-types boil down to primitives is partly dependent on compile time switch conditions. So in short, what primitives they boil down to is installation dependent. It's easy enough to trace things these back to primitives on a given system, (the C preprocessor cpp helps a lot), but that only really supplies that information on a given installation. It really should be computed wherever a PLT scheme script is installed. At this stage I'm starting to feel like I'm reinventing the wheel. Again!. And this time only to accomplish a script. Someone else has already had to cope with this issue and written some useful tools for generating compatible scheme code from C structure declarations. If I had been responsible for any part of PLT scheme, I know I would have done something along those lines. Surely someone else has? For perspective, here is the output of the cpp preprocessor's version of the stat structure on my system. struct stat { __dev_t st_dev; unsigned short int __pad1; __ino_t st_ino; __mode_t st_mode; __nlink_t st_nlink; __uid_t st_uid; __gid_t st_gid; __dev_t st_rdev; unsigned short int __pad2; __off_t st_size; __blksize_t st_blksize; __blkcnt_t st_blocks; struct timespec st_atim; struct timespec st_mtim; struct timespec st_ctim; unsigned long int __unused4; unsigned long int __unused5; }; In the interest of brevity, I clipped the upper part of the preprocessor output where for instance these translations can be gleaned: __dev_t to 'unsigned long long int' __ino_t to 'unsigned long int' __mode_t to 'unsigned int' Is there an existing PLT recommended practise for dealing with these sorts of installation issues? Are there existing recommended tools for deriving necessary scheme interface data from stand library include files? If not are there existing workaround tools and practices being used until recommended ones emerge? _________________________________________________ For list-related administrative tasks: http://list.cs.brown.edu/mailman/listinfo/plt-scheme

When does eqv? differ from eq? , from equal?

Woodhouse Gregory — 2008-10-05T17:40:15

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apply vs dot notation syntax

2008-10-05T10:35:02

Hi all, Probably it was discussed ages ago but could not find any links regarding the following question. Why scheme has 'apply' primitive instead of simple dot notation ? i.e. we can use (f arg1 arg2 . rest-of-args-list) instead of standard: (apply f arg1 arg2 rest-of-args-list) The former looks similar to the 'define' syntax and has advantage to be processed by a compiler in some special way. For example, optimizer can remove some unused arguments. Doing the same optimization with standard approach looks unnatural from the compiler design perspective : compiler [lower layer] should know about function primitives [higher level]. Thanks. -- Bohdan _________________________________________________ For list-related administrative tasks: http://list.cs.brown.edu/mailman/listinfo/plt-scheme

copy-paste from scribble html docs to drscheme

Stephen De Gabrielle — 2008-10-05T08:07:04

Hi, I sometimes copy paste code from the docs into DrScheme; a really frustrating thing happens - every line in the docs is replaces by 10 lines in DrScheme. (see example below) I've attached a picture of the table structure used. Would it be a problem If I looked into other ways of getting the same layout without tables? Cheers, Stephen -- Example source html for on-load-file (five lines)

(send an-editor on-load-file		filename
		format)		→		void?

filename : path?

format

(one-of/c 'guess 'same 'copy 'standard

'text 'text-force-cr)

-- example of pasting editor-snip because I can't remember all the attributes :-) -- (new editor-snip% [ [editor editor] [with-border? with-border?] [left-margin left-margin] [top-margin top-margin] [right-margin right-margin] [bottom-margin bottom-margin] [left-inset left-inset] [top-inset top-inset] [right-inset right-inset] [bottom-inset bottom-inset] [min-width min-width] [max-width max-width] [min-height min-height] [max-height max-height]]) --- _________________________________________________ For list-related administrative tasks: http://list.cs.brown.edu/mailman/listinfo/plt-scheme

I really think this is such a great group!

Geneve — 2008-10-04T17:19:52

I like it! _________________________________________________ For list-related administrative tasks: http://list.cs.brown.edu/mailman/listinfo/plt-scheme

Scheme Programming Question (Boolean Connectives)

Geneve — 2008-10-04T17:13:17

This is another problem that I am having trouble with. I really need your help. Question Details: Exercise 7. The built-in predicate stringlist in your solution, but do not use the built-in string

Scheme Programming Question (Making an error message)

Geneve — 2008-10-04T17:11:43

Can anyone do this? This is my homework, and I am really having trouble with it. Can any smart scientist do this? Question Details: Exercise 13. For Assignment 4, you defined the procedure reverse-list. A call to your version of reverse-list probably resulted in the following sort of error when passed an invalid argument. ------------------------------- (define combine-lists (lambda (a b) (if (null? a) b (combine-lists (cdr a) (cons (car a) b))))) (define reverse-list (lambda (ls) (combine-lists ls '()))) --------------------------------- Error in cdr: 3 is not a pair. Error in cdr: c is not a pair. Define reverse-list using an internally defined help procedure. Have the help procedure signal an error if the incoming argument is not a pair or empty list. Your solution should make only one pass through the list. In particular, you should not use list?, proper-list?, or the equivalent to first check if the list is proper, since this would count as an additional pass through the list. (Of course, you may use the built-in pair? predicate.) (Naturally, you may not use the built- in reverse procedure since the point of the exercise is to implement that procedure.) Identify the error as coming from reverse-list, not from the helper, and show the original input to reverse-list in the error message, even if the error occurs some iterations into the loop. Error in reverse-list: 3 is not a proper list. Error in reverse-list: (a . b) is not a proper list. Error in reverse-list: (a b . c) is not a proper list. (does this work? it should) Hint: The text of this exercise tells exactly how to detect the error. _________________________________________________ For list-related administrative tasks: http://list.cs.brown.edu/mailman/listinfo/plt-scheme

capturing composite mouse events in mred

Stephen De Gabrielle — 2008-10-04T22:19:21

Hi, I'm trying to capture a click on an empty pasteboard, but mouse events only seem to exist in their most basic form. ('mouse-down 'enter 'exit etc.) [I can't be the first person to want to do this?] Have I missed something in the documentation, is there a library, or should I roll my own? Stephen _________________________________________________ For list-related administrative tasks: http://list.cs.brown.edu/mailman/listinfo/plt-scheme

Code for catching exceptions in embedding applications

Sergey Khorev — 2008-10-04T15:02:42

Hi, While trying to migrate an application to PLT 4.1, I stuck with exception handling. Code below (basically it has been extracted from PLT documentation) crashes with #f::0: compile: bad syntax; function application is not allowed, because no #%app syntax transformer is bound in: (lambda (thunk) (with-handlers ((void (lambda(exn) (cons #f exn)))) (cons #t (thunk)))) Seg fault (internal error) at 4 Do I need to `require' some module for this to work? #define MZ_PRECISE_GC 1 #include /* #include "base.c" */ static Scheme_Env *environment = NULL; static int scheme_main(void *data) { char *e = "(lambda (thunk) " "(with-handlers ([void (lambda (exn) (cons #f exn))]) " "(cons #t (thunk))))"; Scheme_Env *env = NULL; Scheme_Object *exn_catching_apply = NULL; Scheme_Object *sym = NULL; MZ_GC_DECL_REG(3); MZ_GC_VAR_IN_REG(0, env); MZ_GC_VAR_IN_REG(1, exn_catching_apply); MZ_GC_VAR_IN_REG(2, sym); MZ_GC_REG(); MZ_REGISTER_STATIC(environment); environment = scheme_basic_env(); /* declare_modules(environment); sym = scheme_intern_symbol("scheme/base"); scheme_namespace_require(sym); */ env = (Scheme_Env *)scheme_make_namespace(0, NULL); exn_catching_apply = scheme_eval_string(e, env); MZ_GC_UNREG(); return 1; } int main() { return scheme_main_stack_setup(1, scheme_main, NULL); } _________________________________________________ For list-related administrative tasks: http://list.cs.brown.edu/mailman/listinfo/plt-scheme

Win32 FFI: Handling structures.

Elena Garrulo — 2008-10-03T12:28:44

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Objects, classes and match

Dave Gurnell — 2008-10-03T12:12:01

Hi all, Is there any way to use match on an object? I can't see anything in the docs (although I may be missing something obvious). Something like: (match (new my-class%) [(struct my-class% (a b c)) ...]) I don't mind setting up a custom match-expander. I suppose I could convert the object to a vector and match on that. That doesn't seem like a particularly efficient solution, though. Cheers,

Where to find out that library objects like "chmod" are available in the underlying implementation?

Ernie Smith — 2008-10-02T21:43:35

I picked this out of the thread: Easy indeed. I tried it. It works. Now here are my questions: 1- Where would I have needed to look to find out that "chmod" is available like that when the lib argument is #f? 2- What other underlying system calls are available? The one that would suit me right now would be 'stat'. I'm attempting to write a script that traverses the file system on a specific device. (fold-files ..) almost does the trick but... I need to prune cross-device directory transitions. That would be easy enough by monitoring transitions in device number using "stat". I also need to ignore all the special files one tends to find on unix systems, i.e. filter for 'regular files' not named pipes, special device files etc.. The frustrating thought I've been having is that in order to implement (fold-files ...) the underlying software is likely using "stat". I'm hoping this post has two effects. 1- A nice quick easy answer like Eli Barzilay came up with for "chmod". 2- This inspires someone on the PLT team to come up with an improved (fold-files ..) that makes the desire for "stat" ffi calls at this level go away. BTW I'm still on 372 TIA _________________________________________________ For list-related administrative tasks: http://list.cs.brown.edu/mailman/listinfo/plt-scheme

Problem with require statements using PLT4.x

Joshua Ewulo — 2008-10-02T16:55:15

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HtDP 17.7.1-4 - Diff between name-of-function andfunction-name

dave yrueta — 2008-10-02T16:23:12

Hi All -- Two questions about exercises 17.4.*. The terms of these exercises suggests a significant difference between a function-name and name-of-function. Is a function-name a symbol and a name-of-function a variable, where A function-definition(fd) is a structure (make-fd f-name p-name f-body) where f-name is a symbol, p-name is a symbol and f-body is a scheme- expression, and; A name-of-function(fn) is the variable in the sentence (define fn fd) where define is a keyword, fn is a variable and fd is function- definition, and; A function-application (fa) is a structure, where (make-fa fn arg) where fn is a name-of-function and arg is a scheme-expression? If this is the case, then I have a follow-up question for exercise 17.7.4: what is the meaning of Step 2, which instructs "evaluate-with- defs" to "look up the definition of P is defs?" Example:, (define(f x) (+ 3 x) is translated to name-of-function (define f (make-fd 'f 'x (make-add 3 'x))), and; (define (h u) (f (* 2 u))) is translated to name-of-function (define h(make-fd 'h 'u(make-fa f (make-mul 2 'u)))) ;;evaluate-with-defs: scheme-expression list-of-defs > error or number ;;consumes a scheme-expression and a list-of-function-definitions: returns an error if the ;;original scheme-expression is not numeric, or if a function found as an arg for a function-;;application is not listed in the list-of-defs; otherwise, returns a number Examples: 1. (not(evaluate-with-defs 3 (list h))), since f is embedded in h, and f is not present in list-of-defs 2. (evaluate-with-defs 3 (list f h)) returns 12 3. (not(evaluate-with-defs (f 3) (list h))) 4. (evaluate-with-defs (f 3) (list f h))) returns 18 My initial solution to this problem is this: (define(evaluate-with-defs sx lofP) (cond [(empty? lofP)(evaluate-expression sx)] [else (evaluate-with-defs(evaluate-with-one-def sx (first lofP)) (rest lofP)))])) The second condition would begin by applying f to 3, returning 6, and then recurring. Next, it would apply h to 6. While doing so, it would find that h is defined as a function-application of f to (* 2 u). At that point, it would "look-up" f in lofP to find its' definition. However, f has already been tossed after the first recursive call, so it would presumably return an error, which is not correct. Is the solution to add a second parameter to evaluate-with-defs: "lofP- index" which would serve as a look-up index for all function- definitions listed in the original "lofP?" If this is the case, then all the previous functions would have to be retrofitted to carry this index parameter. That doesn't seem right. Further, what is the point of "looking-up" the function-definition f in lofP when the function-definition is present in the name-of- function attribute of the function-application? The only way this would make sense to me is if the name-of-function attribute was meant to be a symbol, and not a variable. If that's the case, then my approach to solving this and the previous exercise is wrong. For completeness, here are the rest of my data-definitions and my version of the solution to 17.7.3: Thanks, Dave Yrueta Data Defs: An "add" is a structure (make-add left right) where left and right are both Scheme-Expressions An "mul" is a structure (make-mul left right) where left and right are both Scheme-Expressions A Scheme-Expression (SX) is either 1. a number 2. a symbol 3. an add structure 4. a mul structure 5. a function-application (fa) ;;17.7.3 ;;evaluate-with-one-def: sx P > error or Scheme Expression ;;consumes a Scheme Expression and a Function-Definition, and returns either an 'error ;;or the evaluated Scheme Expression (define(evaluate-with-one-def sx P) (cond [(numeric? sx) (cond [(number? sx)(evaluate-expression(subs(fd-p-name P)sx(fd-f-body P)))] [else(evaluate-with-one-def (evaluate-expression sx)P)])] [else 'error])) ;;subst:symbol number scheme-expression > scheme-expression ;;consumes a symbol, number and scheme-expression, substitutes all instances of the ;;symbol appearing in the scheme-expression with the number, and then returns a ;;structurally equivalent expression. (define(subs sym num sx) (cond [(mul? sx)(make-mul (subs sym num (mul-left sx))(subs sym num (mul- right sx)))] [(add? sx)(make-add (subs sym num (add-left sx))(subs sym num (add- right sx)))] [(fa? sx) (evaluate-with-one-def(subs sym num (fa-arg sx))(fa-fn sx))] [(number? sx)sx] [(symbol=? sym sx)num] [else sx])) (define(numeric? sx) (cond [(number? sx)true] [(struct? sx)(test-struc sx)] [else false])) (define(test-struc sx) (cond [(mul? sx)(and(numeric? (mul-left sx))(numeric? (mul-right sx)))] [else (and(numeric? (add-left sx))(numeric? (add-right sx)))])) (define(evaluate-expression nx) (cond [(boolean=? (numeric? nx)false)'error] [else (process-nx nx)])) (define(process-nx nx) (cond [(number? nx)nx] [(mul? nx)(*(evaluate-expression (mul-left nx))(evaluate- expression (mul-right nx)))] [else (+(evaluate-expression (add-left nx))(evaluate-expression (add-right nx)))])) _________________________________________________ For list-related administrative tasks: http://list.cs.brown.edu/mailman/listinfo/plt-scheme