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Search found 23 results on 1 pages for 'drscheme'.

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• drscheme c# adapter

  - by alan

  Hi guys i need to integrate drscheme into my c# code for my assignment but i could find any luck on the web. Can anyone help me ? I tried ironscheme but got the following error. The type or namespace name 'Dynamic' does not exist in the namespace 'System' (are you missing an assembly reference?) C:\Documents and Settings\Administrator\My Documents\Visual Studio 2008\Projects\Integration\Integration\Form1.cs 2 14 Integration Have tried googling the error message but could find any related stuff.

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• DrScheme versus mzscheme: treatment of definitions

  - by speciousfool

  One long term project I have is working through all the exercises of SICP. I noticed something a bit odd with the most recent exercise. I am testing a Huffman encoding tree. When I execute the following code in DrScheme I get the expected result: (a d a b b c a) However, if I execute this same code in mzscheme by calling (load "2.67.scm") or by running mzscheme -f 2.67.scm, it reports: symbols: expected symbols as arguments, given: (leaf D 1) My question is: why? Is it because mzscheme and drscheme use different rules for loading program definitions? The program code is below. ;; Define an encoding tree and a sample message ;; Use the decode procedure to decode the message, and give the result. (define (make-leaf symbol weight) (list 'leaf symbol weight)) (define (leaf? object) (eq? (car object) 'leaf)) (define (symbol-leaf x) (cadr x)) (define (weight-leaf x) (caddr x)) (define (make-code-tree left right) (list left right (append (symbols left) (symbols right)) (+ (weight left) (weight right)))) (define (left-branch tree) (car tree)) (define (right-branch tree) (cadr tree)) (define (symbols tree) (if (leaf? tree) (list (symbol-leaf tree)) (caddr tree))) (define (weight tree) (if (leaf? tree) (weight-leaf tree) (cadddr tree))) (define (decode bits tree) (define (decode-1 bits current-branch) (if (null? bits) '() (let ((next-branch (choose-branch (car bits) current-branch))) (if (leaf? next-branch) (cons (symbol-leaf next-branch) (decode-1 (cdr bits) tree)) (decode-1 (cdr bits) next-branch))))) (decode-1 bits tree)) (define (choose-branch bit branch) (cond ((= bit 0) (left-branch branch)) ((= bit 1) (right-branch branch)) (else (error "bad bit -- CHOOSE-BRANCH" bit)))) (define (test s-exp) (display s-exp) (newline)) (define sample-tree (make-code-tree (make-leaf 'A 4) (make-code-tree (make-leaf 'B 2) (make-code-tree (make-leaf 'D 1) (make-leaf 'C 1))))) (define sample-message '(0 1 1 0 0 1 0 1 0 1 1 1 0)) (test (decode sample-message sample-tree))

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• How do I profile in DrScheme?

  - by kunjaan

  How Do I profile my functions using DrScheme? (require profile) (define (factorial n) (cond ((= n 1) 1) (else (* n (factorial (- n 1)))))) (profile factorial) The above code returns Profiling results ----------------- Total cpu time observed: 0ms (out of 0ms) Number of samples taken: 0 (once every 0ms) ==================================== Caller Idx Total Self Name+srcLocal% ms(pct) ms(pct) Callee ==================================== > I tried: - (profile (factorial 100)) - (profile factorial) (factorial 100) But it gives me the same result. What am I doing wrong?

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• "unbound identifier" errors in scheme

  - by user186909

  Hello: I'm using drscheme from: http://www.archlinux.org/packages/extra/x86_64/drscheme/ I'm trying to work with the sample code in my textbook, but I keep getting getting "unbound identifier" errors. Is it because the scheme interpreter is not configured correctly? or is the code just plain wrong? Here are a few examples: Input: #lang scheme (define (equalimp lis1 lis2) (COND ((NULL? lis1) (NULL? lis2)) ((NULL? lis2) '()) ((EQ? (CAR lis1) (CAR lis2)) (equalimp (CDR lis1) (CDR lis2))) (ELSE '()) )) Output: Welcome to DrScheme, version 4.2.5 [3m]. Language: scheme; memory limit: 128 MB. expand: unbound identifier in module in: COND Input: #lang scheme (define (quadratic_roots a b c) (LET ( (root_part_over_2a (/ (SQRT (- (* b b) (* 4 a c))) (* 2 a))) (minus_b_over_2a (/ (- 0 b) (* 2 a))) ) (DISPLAY (+ minus_b_over_2a root_part_over_2a)) (NEWLINE) (DISPLAY (- minus_b_over_2a root_part_over_2a)) )) Output: expand: unbound identifier in module in: LET Note: I tried using LET* because I read this: stackoverflow.com/ questions/946050/using-let-in-scheme but it produces the same error. Thanks !

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• Graph representation in Dr Scheme

  - by John Retallack

  I want to represent a graph in Dr. Scheme in the following manner: For each node I want to store it's value and a list of adjacent nodes,the problem which i'm having difficulties with is that I want the adjacent nodes to be stored as references to other nodes. For example: I want node ny to be stored as („NY“ (l p)) where l and p are adjacent nodes,and not as („NY“ („London“ „Paris“)).

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• Matrix addition in Scheme

  - by user285012

  I am trying to add a matrix and it is not working... (define (matrix-matrix-add a b) (map (lambda (row) (row-matrix-add row b)) a)) (define (row-matrix-add row matrix) (if (null? (car matrix)) '() (cons (add-m row (map car matrix)) (row-matrix-add row (map cdr matrix))))) (define (add-m row col) (if (null? col) 0 (+ (car row) (car col) (add-m (cdr row) (cdr col)))))

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• Cartesian product in Scheme

  - by John Retallack

  I've been trying to do a function that returns the Cartesian Product of n sets,in Dr Scheme,the sets are given as a list of lists,I've been stuck at this all day,I would like a few guidelines as where to start,I've wrote a pice of code but it dosen't work. (define cart-n(?(l) (if (null? l) '(()) (map (?(lst) (cons (car ( car(l))) lst)) (cart-n (cdr l) )))))

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• cartesian product

  - by John Retallack

  I've been trying to do a function that returns the Cartesian Product of n sets,in Dr Scheme,the sets are given as a list of lists,I've been stuck at this all day,I would like a few guidelines as where to start,I've wrote a pice of code but it dosen't work. (define cart-n(?(l) (if (null? l) '(()) (map (?(lst) (cons (car ( car(l))) lst)) (cart-n (cdr l) )))))

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• PLT Scheme sort function

  - by Danny

  PLT Scheme guide says that it's implemented sort function is able to sort a list according to an extarcted value using a lambda function. link text The guide provides an unworking code example of this- (sort '(("aardvark") ("dingo") ("cow") ("bear")) #:key car string<?) Which returns an error. How is this function is supposed to be calles so that it will actually sort a list according to values calculated by a given function?

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• Recursive breadth first tree traversal

  - by dugogota

  I'm pulling my hair out trying to figure out how to implement breadth first tree traversal in scheme. I've done it in Java and C++. If I had code, I'd post it but I'm not sure how exactly to begin. Given the tree definition below, how to implement breadth first search using recursion? (define tree1 '( A ( B (C () ()) (D () ()) ) (E (F () ()) (G () ())) )) Any help, any, is greatly appreciated.

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• how to solve nested list programs [closed]

  - by riya

  write a function to get most popular car that accepts a car detail as input and returns the most popular car name along with its average rating .Each element of car details list is a sublist that provides the below information about a car (a)name of a car(b)car price (c) list of ratings obtained by car from various agencies.Incase two cars have the same average rating then the car with the lesser price qualifies as most popular car? here's my solution-: (define-struct cardetails ("name" price list of '(ratings)) (define car1 (make-cardetails "toyota" 123 '( 1 2 3))) (define car2 (make-cardetails "santro" 321 '( 2 2 3))) (define car3 (make-cardetails "toyota" 100 '( 1 2 3))) (define cardetailslist(list(car1) (car2)(car 3))) (let loop ((count 0)) (let (len (length cardetailslist)) (if(< count len) (string-ref (string-ref n)0) now please tell me how to find maximum average and display car name.it's not a homework question tomorrow is my test and we have not been taught this concept in class although it is very important from test point of view

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• In SICP exercise 2.26 using DrScheme, why does cons return a list, instead of a pair of lists?

  - by limist

  In SICP exercise 2.26, this Scheme code is given: (define x (list 1 2 3)) (define y (list 4 5 6)) Then this cons call is given: (cons x y) I expected a pair of lists would result, ((1 2 3) (4 5 6)) but the interpreter gives, ((1 2 3) 4 5 6) ...a list with 4 elements, the first being a list. Why is y treated differently? I've tried looking up other SICP answers for an explanation, but couldn't find something satisfactory. So could any Scheme/Lisp experts please shed some light on this aspect of cons? Thanks in advance for any insight.

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• How to print structures in PLT Scheme so as to display their fields?

  - by tkf

  I would like code like this: (define-struct thing (a b c)) (define th (make-thing 1 2 3)) to print something like this: (make-thing 1 2 3) when I type "th" into either the DrScheme or MzScheme repl. I am using the language "pretty big" in DrScheme with output style set to "constructor". This is what I get in DrScheme: (make-thing ...) (i literally get the three dots) In MzScheme: #<thing>

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• Is there an equivalent to Lisp's "runtime" primitive in Scheme?

  - by Bill the Lizard

  According to SICP section 1.2.6, exercise 1.22: Most Lisp implementations include a primitive called runtime that returns an integer that specifies the amount of time the system has been running (measured, for example, in microseconds). I'm using DrScheme, where runtime doesn't seem to be available, so I'm looking for a good substitute. I found in the PLT-Scheme Reference that there is a current-milliseconds primitive. Does anyone know if there's a timer in Scheme with better resolution?

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• Running Scheme from the command line

  - by Pranav

  How do you run Scheme programs from the terminal in linux(ubuntu)? Also how to accept arguments from the command-line in a Scheme program? Edit: Im using the DrScheme implementation.

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• Do you have to use display to output stuff using r6rs?

  - by incrediman

  Background: I am new to scheme, and am using DrScheme to write my programs. The following program outputs 12345 when I run the program as r5rs: 12345 However the following program outputs nothing (it's an r6rs program): #!r6rs (import (rnrs)) 12345 That being said, I can get it to output 12345 by doing this: #!r6rs (import (rnrs)) (display 1235) Is that something new with r6rs, where output only occurs when specifically specified using display? Or am I just doing something else wrong

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• Scheme implementations - what does it mean?

  - by JDelage

  Hi, I'm a beginning student in CS, and my classes are mostly in Java. I'm currently going through "Little Schemer" as a self study, and in the process of finding out how to do that I have found numerous references to "implementations" of Scheme. My question is, what are implementations? Are they sub-dialects of Scheme, or is that something else (DrScheme seem to allow for different "flavors" of the language)? Is it just the name given to any given ecosystem incorporating an IDE, interpreter, interactive tool and the like? Do all other languages (e.g., Java) also have a variety of "implementations", or is it something reserved to "open" languages? Thank you, Joss Delage

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• How do I write Push and Pop in Scheme?

  - by kunjaan

  Right now I have (define (push x a-list) (set! a-list (cons a-list x))) (define (pop a-list) (let ((result (first a-list))) (set! a-list (rest a-list)) result)) But I get this result: Welcome to DrScheme, version 4.2 [3m]. Language: Module; memory limit: 256 megabytes. > (define my-list (list 1 2 3)) > (push 4 my-list) > my-list (1 2 3) > (pop my-list) 1 > my-list (1 2 3) What am I doing wrong? Is there a better way to write push so that the element is added at the end and pop so that the element gets deleted from the first?

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• Extra line breaks inserted in MrEd text%

  - by Jesse Millikan

  In a DrScheme project, I'm using a MrEd editor-canvas% with text% and inserting a string from a literal in a Scheme file. This results in an extra blank line in the editor for each line of text I'm trying to insert. Is this a Windows vs. Unix linebreak problem? I can't find anything about text% treats line breaks in the documentation. ; Inside a class definition: (define/public (edit-pattern p j b d h) (send input-beat set-value (number->string b)) (send input-dwell set-value (number->string d)) (send hold-beats set-value (number->string h)) (send juggler-t erase) ; Why do these add extra newlines (send juggler-t insert j) (send pattern-t erase) (send pattern-t insert p)) (define juggler-ec (new editor-canvas% [parent this] [line-count 12])) (define juggler-t (new text%)) (send juggler-ec set-editor juggler-t) (define pattern-ec (new editor-canvas% [parent this] [line-count 20])) (define pattern-t (new text%)) (send pattern-ec set-editor pattern-t) ; Lots of other stuff...

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• What Scheme Does Ghuloum Use?

  - by Don Wakefield

  I'm trying to work my way through Compilers: Backend to Frontend (and Back to Front Again) by Abdulaziz Ghuloum. It seems abbreviated from what one would expect in a full course/seminar, so I'm trying to fill in the pieces myself. For instance, I have tried to use his testing framework in the R5RS flavor of DrScheme, but it doesn't seem to like the macro stuff: src/ghuloum/tests/tests-driver.scm:6:4: read: illegal use of open square bracket I've read his intro paper on the course, An Incremental Approach to Compiler Construction, which gives a great overview of the techniques used, and mentions a couple of Schemes with features one might want to implement for 'extra credit', but he doesn't mention the Scheme he uses in the course. Update I'm still digging into the original question (investigating options such as Petit Scheme suggested by Eli below), but found an interesting link relating to Gholoum's work, so I am including it here. [Ikarus Scheme](http://en.wikipedia.org/wiki/Ikarus_(Scheme_implementation)) is the actual implementation of Ghuloum's ideas, and appears to have been part of his Ph.D. work. It's supposed to be one of the first implementations of R6RS. I'm trying to install Ikarus now, but the configure script doesn't want to recognize my system's install of libgmp.so, so my problems are still unresolved. Example The following example seems to work in PLT 2.4.2 running in DrEd using the Pretty Big (require lang/plt-pretty-big) (load "/Users/donaldwakefield/ghuloum/tests/tests-driver.scm") (load "/Users/donaldwakefield/ghuloum/tests/tests-1.1-req.scm") (define (emit-program x) (unless (integer? x) (error "---")) (emit " .text") (emit " .globl scheme_entry") (emit " .type scheme_entry, @function") (emit "scheme_entry:") (emit " movl $~s, %eax" x) (emit " ret") ) Attempting to replace the require directive with #lang scheme results in the error message foo.scm:7:3: expand: unbound identifier in module in: emit which appears to be due to a failure to load tests-driver.scm. Attempting to use #lang r6rs disables the REPL, which I'd really like to use, so I'm going to try to continue with Pretty Big. My thanks to Eli Barzilay for his patient help.

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• Strings exported from a module have changed line breaks

  - by Jesse Millikan

  In a DrScheme project, I'm using a MrEd editor-canvas% with text% and inserting a string from a literal in a Scheme file. This results in an extra blank line in the editor for each line of text I'm trying to insert. I've tracked this down to the apparent fact that string literals from outside modules are getting extra line breaks. Here's a full example. The editor is irrelevant at this point, but it displays the result. ; test-literals.ss (module test-literals scheme (provide (all-defined-out)) (define exported-string "From another module with some more line breaks. ")) ; editor-test.ss (module editor-test scheme (require mred "test-literals.ss") (define w (instantiate frame% ("Editor Test" #f) )) (define c (instantiate editor-canvas% (w) (line-count 12) (min-width 400))) (define editor (instantiate text% ())) (send c set-editor editor) (send w show #t) (send editor erase) (send editor insert "Some text with some line breaks. ") (send editor insert exported-string)) And the result in the editor is Some text with some line breaks. From another module with some more line breaks. I've traced in and figured out that it's changing Unix line breaks to Windows line breaks when strings are imported from another module, but these display as double line breaks. Why is this happening and is there a way to stop it other than changing every imported string?

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• Strings exported from a module have extra line breaks

  - by Jesse Millikan

  In a DrScheme project, I'm using a MrEd editor-canvas% with text% and inserting a string from a literal in a Scheme file. This results in an extra blank line in the editor for each line of text I'm trying to insert. I've tracked this down to the apparent fact that string literals from outside modules are getting extra line breaks. Here's a full example. The editor is irrelevant at this point, but it displays the result. ; test-literals.ss (module test-literals scheme (provide (all-defined-out)) (define exported-string "From another module with some more line breaks. ")) ; editor-test.ss (module editor-test scheme (require mred "test-literals.ss") (define w (instantiate frame% ("Editor Test" #f) )) (define c (instantiate editor-canvas% (w) (line-count 12) (min-width 400))) (define editor (instantiate text% ())) (send c set-editor editor) (send w show #t) (send editor erase) (send editor insert "Some text with some line breaks. ") (send editor insert exported-string)) And the result in the editor is Some text with some line breaks. From another module with some more line breaks.

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• Why does Scala apply thunks automatically, sometimes?

  - by Anonymouse

  At just after 2:40 in ShadowofCatron's Scala Tutorial 3 video, it's pointed out that the parentheses following the name of a thunk are optional. "Buh?" said my functional programming brain, since the value of a function and the value it evaluates to when applied are completely different things. So I wrote the following to try this out. My thought process is described in the comments. object Main { var counter: Int = 10 def f(): Int = { counter = counter + 1; counter } def runThunk(t: () => Int): Int = { t() } def main(args: Array[String]): Unit = { val a = f() // I expect this to mean "apply f to no args" println(a) // and apparently it does val b = f // I expect this to mean "the value f", a function value println(b) // but it's the value it evaluates to when applied to no args println(b) // and the evaluation happens immediately, not in the call runThunk(b) // This is an error: it's not println doing something funny runThunk(f) // Not an error: seems to be val doing something funny } }   To be clear about the problem, this Scheme program (and the console dump which follows) shows what I expected the Scala program to do. (define counter (list 10)) (define f (lambda () (set-car! counter (+ (car counter) 1)) (car counter))) (define runThunk (lambda (t) (t))) (define main (lambda args (let ((a (f)) (b f)) (display a) (newline) (display b) (newline) (display b) (newline) (runThunk b) (runThunk f)))) > (main) 11 #<procedure:f> #<procedure:f> 13   After coming to this site to ask about this, I came across this answer which told me how to fix the above Scala program: val b = f _ // Hey Scala, I mean f, not f() But the underscore 'hint' is only needed sometimes. When I call runThunk(f), no hint is required. But when I 'alias' f to b with a val then apply it, it doesn't work: the evaluation happens in the val; and even lazy val works this way, so it's not the point of evaluation causing this behaviour.   That all leaves me with the question: Why does Scala sometimes automatically apply thunks when evaluating them? Is it, as I suspect, type inference? And if so, shouldn't a type system stay out of the language's semantics? Is this a good idea? Do Scala programmers apply thunks rather than refer to their values so much more often that making the parens optional is better overall? Examples written using Scala 2.8.0RC3, DrScheme 4.0.1 in R5RS.

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