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  • How to compile scheme into native binary files ?

    - by Joe
    I am very new to scheme. And now I am trying to compile some scheme code into binary file which will be loaded faster into interpreter. (The interpreter is a hybrid interpreter)Some one told me that I can compile the code into native binary file and then load it into interperter. And my question is: 1. What is the native binary file? 2. How can I compile the scheme code into a native binary file? 3. How can I load native bianry file into scheme interpreter? Thanks in advance. Joe Suggested that I want to compile below code into native binary file: (define test (lambda() (display "this is a test")) And then load the bianry file into interpreter and call the function "test".

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  • What software has been written in Scheme?

    - by skiphoppy
    I loved Scheme in the programming languages concepts class I took several years ago. Ever since reading what Paul Graham has to say about Lisp, I've been intending to go back and pick Scheme up again and see if it'll improve my programming in general. Are there any well-known works of software written in Scheme? Open source packages? Websites?

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  • Does Scheme work with Microsoft COM?

    - by Martin
    I'm new to Scheme -- the functional programming language and I like it a lot for its first-class/higher-order functions. However, my data comes from a COM source with an object-oriented API. I know Scheme and COM belong to different programming paradigms, but I'm wondering if there is any interface or a way for Scheme to connect to a COM source? Thanks.

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  • How do I learn Scheme?

    - by Gautam
    Hey, I'm a relative newbie to programming. I've picked up some very basic Java (File I/O, GUIs, inheritance) and would like to take a look at functional programming - in particular, I would like to learn Scheme. I'm having some trouble finding a Scheme implementation I can understand. Interpreters are weird; I'm not sure how to save my programs and create executables. I've downloaded PLT Scheme, but I would prefer using something less condescending, something similar to NetBeans. Is there a plugin or tool that will allow me to quickly and easily create and manage Scheme programs? All help is appreciated!

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  • If Scheme is untyped, how can it have numbers and lists?

    - by Dokkat
    Scheme is said to be just an extension of the Untyped Lambda Calculus (correct me if I am wrong). If that is the case, how can it have Lists and Numbers? Those, to me, look like 2 base types. So I'd say Racket is actually an extension of the Simply Typed Lambda Calculus. No? Question: Is Scheme's type system actually based or more similar to Simply Typed or Untyped Lambda Calculus? In what ways does it differ from Untyped and or Simply Typed Lambda Calculus? (The same question is valid for "untyped" languages such as Python and JavaScript - all of which look like they have base types to me.)

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  • Idiomatic usage of filter, map, build-list and local functions in Racket/Scheme?

    - by Greenhorn
    I'm working through Exercise 21.2.3 of HtDP on my own and was wondering if this is idiomatic usage of the various functions. This is what I have so far: (define-struct ir (name price)) (define list-of-toys (list (make-ir 'doll 10) (make-ir 'robot 15) (make-ir 'ty 21) (make-ir 'cube 9))) ;; helper function (define (price< p toy) (cond [(< (ir-price toy) p) toy] [else empty])) (define (eliminate-exp ua lot) (cond [(empty? lot) empty] [else (filter ir? (map price< (build-list (length lot) (local ((define (f x) ua)) f)) lot))])) To my novice eyes, that seems pretty ugly because I have to define a local function to get build-list to work, since map requires two lists of equal length. Can this be improved for readability? Thank you.

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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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  • How do you perform arithmetic calculations on symbols in Scheme/Lisp?

    - by kunjaan
    I need to perform calculations with a symbol. I need to convert the time which is of hh:mm form to the minutes passed. ;; (get-minutes symbol)->number ;; convert the time in hh:mm to minutes ;; (get-minutes 6:19)-> 6* 60 + 19 (define (get-minutes time) (let* ((a-time (string->list (symbol->string time))) (hour (first a-time)) (minutes (third a-time))) (+ (* hour 60) minutes))) This is an incorrect code, I get a character after all that conversion and cannot perform a correct calculation. Do you guys have any suggestions? I cant change the input type. Context: The input is a flight schedule so I cannot alter the data structure. ;; ---------------------------------------------------------------------- Edit: Figured out an ugly solution. Please suggest something better. (define (get-minutes time) (let* ((a-time (symbol->string time)) (hour (string->number (substring a-time 0 1))) (minutes (string->number (substring a-time 2 4)))) (+ (* hour 60) minutes)))

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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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  • Need to combine a color, mask, and sprite layer in a shader

    - by Donutz
    My task: to display a sprite using different team colors. I have a sprte graphic, part of which has to be displayed as a team color. The color isn't 'flat', i.e. it shades from brighter to darker. I can't "pre-build" the graphics because there are just too many, so I have to generate them at runtime. I've decided to use a shader, and supply it with a texture consisting of the team color, a texture consisting of a mask (black=no color, white=full color, gray=progressively dimmed color), and the sprite grapic, with the areas where the team color shows being transparent. So here's my shader code: // Effect attempts to merge a color layer, a mask layer, and a sprite layer // to produce a complete sprite sampler UnitSampler : register(s0); // the unit sampler MaskSampler : register(s1); // the mask sampler ColorSampler : register(s2); // the color float4 main(float4 color : COLOR0, float2 texCoord : TEXCOORD0) : COLOR0 { float4 tex1 = tex2D(ColorSampler, texCoord); // get the color float4 tex2 = tex2D(MaskSampler, texCoord); // get the mask float4 tex3 = tex2D(UnitSampler,texCoord); // get the unit float4 tex4 = tex1 * tex2.r * tex3; // color * mask * unit return tex4; } My problem is the calculations involving tex1 through tex4. I don't really understand how the manipulations work, so I'm just thrashing around, producing lots of different incorrect effects. So given tex1 through tex3, what calcs do I do in order to take the color (tex1), mask it (tex2), and apply the result to the unit if it's not zero? And would I be better off to make the mask just on/off (white/black) and put the color shading in the unit graphic?

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  • Best way to blend colors in tile lighting? (XNA)

    - by Lemoncreme
    I have made a color, decent, recursive, fast tile lighting system in my game. It does everything I need except one thing: different colors are not blended at all: Here is my color blend code: return (new Color( (byte)MathHelper.Clamp(color.R / factor, 0, 255), (byte)MathHelper.Clamp(color.G / factor, 0, 255), (byte)MathHelper.Clamp(color.B / factor, 0, 255))); As you can see it does not take the already in place color into account. color is the color of the previous light, which is weakened by the above code by factor. If I wanted to blend using the color already in place, I would use the variable blend. Here is an example of a blend that I tried that failed, using blend: return (new Color( (byte)MathHelper.Clamp(((color.R + blend.R) / 2) / factor, 0, 255), (byte)MathHelper.Clamp(((color.G + blend.G) / 2) / factor, 0, 255), (byte)MathHelper.Clamp(((color.B + blend.B) / 2) / factor, 0, 255))); This color blend produces inaccurate and strange results. I need a blend that is accurate, like the first example, that blends the two colors together. What is the best way to do this?

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  • What is the best color combination for readability, easy of use, and reduced eye strain?

    - by Nick Berardi
    I am trying to pick out the optimal set of colors for a new website project. I want to do a traditional black on white look and feel for the main content. However my partner on the project wants to do a color combination that more looks like the traditional Windows Forms look and feel. Is there any research available on the best color combination's to use for readability, ease of use, and reduced eye strain?

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  • scheme basic loop

    - by utku
    I'm trying to write a scheme func that behaves in a way similar to a loop. (loop min max func) This loop should perform the func between the range min and max (integers) -- one of an example like this (loop 3 6 (lambda (x) (display (* x x)) (newline))) 9 16 25 36 and I define the function as ( define ( loop min max fn) (cond ((>= max min) ( ( fn min ) ( loop (+ min 1 ) max fn) ) ) ) ) when I run the code I get the result then an error occur. I couldn't handle this error. (loop 3 6 (lambda (x) (display(* x x))(newline))) 9 16 25 36 Backtrace: In standard input: 41: 0* [loop 3 6 #] In utku1.scheme: 9: 1 (cond ((= max min) ((fn min) (loop # max fn)))) 10: 2 [# ... 10: 3* [loop 4 6 #] 9: 4 (cond ((= max min) ((fn min) (loop # max fn)))) 10: 5 [# ... 10: 6* [loop 5 6 #] 9: 7 (cond ((= max min) ((fn min) (loop # max fn)))) 10: 8 [# ... 10: 9* [loop 6 6 #] 9: 10 (cond ((= max min) ((fn min) (loop # max fn)))) 10: 11 [# #] utku1.scheme:10:31: In expression ((fn min) (loop # max ...)): utku1.scheme:10:31: Wrong type to apply: #<unspecified> ABORT: (misc-error)

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  • Why isn't there a good scheme/lisp on llvm?

    - by anon
    There is Gambit scheme, MIT scheme, PLT scheme, chicken scheme, bigloo, larceny, ...; then there are all the lisps. Yet, there's not (to my knowledge) a single popular scheme/lisp on LLVM, even though LLVM provides lots of nice things like: easier to generate code than x85 easy to make C ffi calls ... So why is it that there isn't a good scheme/lisp on LLVM?

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  • Is Reading the Spec Enough?

    - by jozefg
    This question is centered around Scheme but really could be applied to any LISP or programming language in general. Background So I recently picked up Scheme again having toyed with it once or twice before. In order to solidify my understanding of the language, I found the Revised^5 Report on the Algorithmic Language Scheme and have been reading through that along with my compiler/interpreter's (Chicken Scheme) listed extensions/implementations. Additionally, in order to see this applied I have been actively seeking out Scheme code in open source projects and such and tried to read and understand it. This has been sufficient so far for me understanding the syntax of Scheme and I've completed almost all of the Ninety-nine Scheme problems (see here) as well as a decent number of Project Euler problems. Question While so far this hasn't been an issue and my solutions closely match those provided, am I missing out on a great part of Scheme? Or to phrase my question more generally, does reading the specification of a language along with well written code in that language sufficient to learn from? Or are other resources, books, lectures, videos, blogs, etc necessary for the learning process as well.

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  • Adding an element to a list in Scheme

    - by user272483
    I'm using R5RS Scheme and I just want to implement a function that returns the intersection of two given lists, but I can't do that because I cannot add an element to a list. Here is my code. How can I fix it? I'm really a beginner in Scheme - this is my first work using Scheme. thx in advance.. (define list3 '()) (define (E7 list1 list2) (cond ((null? list1) list3) ((member (car list1) list2) (append list3 (list (car list1)))) ) (cond ((null? list1) list3) ((not(null? list1)) (E7 (cdr list1) list2) ) ) ) (E7 '(4 5) '(3 4))

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  • Inheritance classes in Scheme

    - by DreamWalker
    Now I research OOP-part of Scheme. I can define class in Scheme like this: (define (create-queue) (let ((mpty #t) (the-list '())) (define (enque value) (set! the-list (append the-list (list value))) (set! mpty #f) the-list) (define (deque) (set! the-list (cdr the-list)) (if (= (length the-list) 0) (set! mpty #t)) the-list) (define (isEmpty) mpty) (define (ptl) the-list) (define (dispatch method) (cond ((eq? method 'enque) enque) ((eq? method 'deque) deque) ((eq? method 'isEmpty) isEmpty) ((eq? method 'print) ptl))) dispatch)) (Example from css.freetonik.com) Can I implement class inheritance in Scheme?

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  • Suggest resources for learning Scheme.

    - by EmFi
    I'll be starting a new job soon where Scheme is heavily used. I currently do not know Scheme, but my employer assures me that is not a problem. Regardless I'd like to hit the ground running and have a working knowledge of the language before my start date. So I'm looking for good resources from which to learn Scheme. I have had minimal exposure to functional languages. Really only a small chunk of a course devoted to Haskell. But I have a strong background in procedural and OO and procedural languages. Before it gets requested by a commenter, I am competent with the following languages: C, C++, C#, Java, Perl, Python, and Ruby.

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  • Color blindness: Are you aware of it? Do you design for it?

    - by User
    I'm curious whether many of us who do design or take design decisions have ever heard of this problem. I'm aware there are dangerous color combinations, like green + red. This is probably one of the most popular cases of color blindness. If you have green text on a red background and vice versa some people won't see anything. I've also seen in practice that green text on a blue background was not seen by one guy. What other color compositions should be avoided, and how often these cases are to be expected? Let us make some ranging by encounter probability who has the numbers. Addition: I've just remembered one very bad example that causes problems to just about everyone - blue text on a black background. It's unreadable for all intents and purposes. Never could understand what could possibly compel a web master to use this color combination...

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  • Can a 10-bit monitor connection preserve all tones in 8-bit sRGB gradients on a wide-gamut monitor?

    - by hjb981
    This question is about color management and the use of a higher color depth, 10 bits per channel (30 bits in total, resulting in 1.07 billion colors, or 1024 shades of gray, sometimes referred to as "deep color") compared to the standard of 8 bits per channel (24 bits in total, 16.7 million colors, 256 shades of gray, sometimes referred to as "true color"). Do not confuse with "32 bit color", which usually refers to standard 8 bit color with an extra channel ("alpha channel") for transparency (used to achieve effects like semi-transparent windows etc). The following can be assumed to be in place: 1: A wide-gamut monitor that supports 10-bit input. Further, it can be assumed that the monitor has been calibrated to its native gamut and that an ICC color profile has been created. 2: A graphics card that supports 10-bit output (and is connected to the monitor via DisplayPort). 3: Drivers for the graphics card that support 10-bit output. If applications that support 10-bit output and color profiles would be used, I would expect them to display images that were saved using different color spaces correctly. For example, both an sRGB and an adobeRGB image should be displayed correctly. If an sRGB image was saved using 8 bits per channel (almost always the case), then the 10-bit signal path would ensure that no tonal gradients were lost in the conversion from the sRGB of the image to the native color space of the monitor. For example: If the image contains a pixel that is pure red in 8 bits (255,0,0), the corresponding value in 10 bits would be (1023,0,0). However, since the monitor has a larger color space than sRGB, sending the signal (1023,0,0) to the monitor would result in a red that was too saturated. Therefore, according to the ICC color profile, the signal would be transformed into a different value with less red saturation, for example (987,0,0). Since there are still plenty of levels left between 0 and 987, all 256 values (0-255) for red in the sRGB color space of the file could be uniquely mapped to color-corrected 10-bit values in the monitor's native color space. However, if the conversion was done in 8 bits, (255,0,0) would be translated to (246,0,0), and there would now only be 247 available levels for the red channel instead of 256, degrading the displayed image quality. My question is: how does this work on Ubuntu? Let's say that I use Firefox (which is color-aware and uses ICC color profiles). Would I get 10-bit processing, thus preserving all levels of an 8-bit picture? What is the situation like for other applications, especially photo applications like Shotwell, Rawtherapee, Darktable, RawStudio, Photivo etc? Does Ubuntu differ from other operating systems (Linux and others) on this point?

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  • Are there people using scheme out there?

    - by Nick
    Hey, I have just started to study computer sciences at the university where they teach us programming in scheme. Since i have learned c++ for the last 6 years, scheme appears a little odd to me. But they tell me you can write any program you can write in C or Java with it. Is anybody really using this language?

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