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  • What's the point of some of shoulda's macros?

    - by ryeguy
    I think shoulda is really neat, but what I don't understand is why some of the macros exist, such as: should_validate_uniqueness_of :title should_validate_presence_of :body, :message => /wtf/ should_validate_presence_of :title should_validate_numericality_of :user_id I'm relatively new to testing, but what purpose do these serve? They're almost an exact mirror of the same validations that happen in the model. For example, what exactly do you accomplish by going into your model and writing validates_uniqueness_of :title and then writing a test that says should_validate_uniqueness_of :title?

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  • Visual Studio Property Page Inherit Macros From Other Projects

    - by James
    So I am having a very difficult time finding a solution to this problem. Is there any way that I can inherit macros from another project. For example, for the post build I would like to use the macro for the RemoteMachine address that is located in one project in all the other projects. I was thinking something like (ProjectContainingMacro.$RemoteMachine) ... does anyone have any suggestions?

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  • Functional Programming - Lots of emphasis on recursion, why?

    - by peakit
    I am getting introduced to Functional Programming [FP] (using Scala). One thing that is coming out from my initial learnings is that FPs rely heavily on recursion. And also it seems like, in pure FPs the only way to do iterative stuff is by writing recursive functions. And because of the heavy usage of recursion seems the next thing that FPs had to worry about were StackoverflowExceptions typically due to long winding recursive calls. This was tackled by introducing some optimizations (tail recursion related optimizations in maintenance of stackframes and @tailrec annotation from Scala v2.8 onwards) Can someone please enlighten me why recursion is so important to functional programming paradigm? Is there something in the specifications of functional programming languages which gets "violated" if we do stuff iteratively? If yes, then I am keen to know that as well. PS: Note that I am newbie to functional programming so feel free to point me to existing resources if they explain/answer my question. Also I do understand that Scala in particular provides support for doing iterative stuff as well.

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  • Default type-parametrized function literal class parameter

    - by doom2.wad
    Is this an intended behavior or is it a bug? Consider the following trait (be it a class, doesn't matter): trait P[T] { class Inner(val f: T => Unit = _ => println("nope")) } This is what I would have expected: scala> val p = new P[Int] { | val inner = new Inner | } p: java.lang.Object with P[Int]{def inner: this.Inner} = $anon$1@12192a9 scala> p.inner.f(5) nope But this? scala> val p = new P[Int] { | val inner = new Inner() { | println("some primary constructor code in here") | } | } <console>:6: error: type mismatch; found : (T) => Unit required: (Int) => Unit val inner = new Inner() { ^

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  • how to translate Haskell into Scalaz?

    - by TOB
    One of my high school students and I are going to try to do a port of Haskell's Parsec parser combinator library into Scala. (It has the advantage over Scala's built-in parsing library that you can pass state around fairly easily because all the parsers are monads.) The first hitch I've come across is trying to figure out how Functor works in scalaz. Can someone explain how to convert this Haskell code: data Reply s u a = Ok a !(State s u) ParseError | Error ParseError instance Functor (Reply s u) where fmap f (Ok x s e) = Ok (f x) s e fmap _ (Error e) = Error e -- XXX into Scala (using Scalaz, I assume). I got as far as sealed abstract class Reply[S, U, A] case class Ok[S, U, A](a: A, state: State[S, U], error: ParseError) extends Reply[S, U, A] case class Error[S, U, A](error: ParseError) extends Reply[S, U, A] and know that I should make Reply extend the scalaz.Functor trait, but I can't figure out how to do that. (Mostly I'm having trouble figuring out what the F[_] parameter does.) Any help appreciated! Thanks, Todd

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  • What is the most efficient functional version of the following imperative code?

    - by justin.r.s.
    I'm learning Scala and I want to know the best way of expressing this imperative pattern using Scala's functional programming capabilities. def f(l: List[Int]): Boolean = { for (e <- l) { if (test(e)) return true } } return false } The best I can come up with is along the lines of: l map { e => test(e) } contains true But this is less efficient since it calls test() on each element, whereas the imperative version stops on the first element that satisfies test(). Is there a more idiomatic functional programming technique I can use to the same effect? The imperative version seems awkward in Scala.

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  • Tied up with injection implemented with setter functions

    - by puudeli
    Hi, I'm trying to use Scala as part of an existing Java application and now I run into an issue with dependencies injected with a setter method (no DI frameworks in this part of code). How is this handled in a Scala way? In Scala both val and var require to be initialized when declared but I can't do that, since the Java setters inject objects that implement a certain interface and interfaces are abstract and can not be instantiated. class ScalaLogic { var service // How to initialize? def setService (srv: OutputService) = { service = srv } Is there a way to initialize the var service so that I can later assign a dependency into it? It should be lexically scoped to be visible in the whole class.

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  • Play Framework Form "fold" method naming rationale

    - by oym
    Play Framework's (2.x) Form class has a method called fold who's usage is indicated as: anyForm.bindFromRequest().fold( f => redisplayForm(f), t => handleValidFormSubmission(t) ) Essentially, the first function parameter is what gets executed on binding failure, and the 2nd on binding success. To me it seems similar to the 'success' and 'error' callbacks of jquery's ajax function. My question is why did the Play developers call the method "fold"? As a disclaimer I am new to Scala, but I am failing to see the connection between this and the functional Scala fold operation. The only similarity is that it is a higher order function; but I don't see any combining that is taking place, nor does it delegate internally in its implementation to any of the Scala fold functions.

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  • Excel data into PowerPoint slides

    - by nqw1
    I have already found some helpful sites but I'm still unable to do what I want. My Excel file contains few columns and multiple rows. All the data from one row would be in one slide but data from different cells in that one row should go to a specific elements in PP slide. At first, is it possible to export data from an Excel cell into a specific text box in PP? For example, I would like to have all data from the first column of each row go to a Text box 1. Let's say I have 100 rows so I would have 100 slides and each slide would have Text bow 1 with correct data. Text box of slide 66 would have data from the first column of row 66. Then all data from the second column of each row would go to a text bow 2 and so on. I tried to do some macros with bad success. I also tried to use Word outlines and export them into PP (New slide - Slides from Outline) but there seems to be a bug since I got 250 pages of gibberish. I had only two paragraphs and both had one word. First paragraph used Heading 1 style and second paragraph used Normal style. Sites what I have found, use VB and/or some other programming language to create slides from Excel sheets. I have tried to add those VB codes into my macros but none of them hasn't worked so far. Probably I just don't know how to use them correctly :) Here's some helpful sites: VBA: Create PowerPoint Slide for Each Row in Excel Workbook Creating a Presentation Report Based on Data Question in Stackoverflow I use Office 2011 on Mac. Any help would be appreciated!

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  • Trees and macros with tikz

    - by Tsf
    I am trying to build my trees using macros but I don't get the result I want. Here is a minimal example: \documentclass{article} \usepackage{tikz} \usetikzlibrary{trees} \newcommand{\LeafNode}[1]{% child {node {#1}} } \newcommand{\InnerNode}[3]{% child {node {#3} #1 #2 } } \begin{document} \begin{tikzpicture} \node (A) {A} \LeafNode{B} \LeafNode{C} ; \end{tikzpicture}% \hspace{2cm}% \begin{tikzpicture} \node (A) {A} \InnerNode{\LeafNode{D}}{\LeafNode{E}}{B} \LeafNode{C} ; \end{tikzpicture} \end{document} I expected this to produce two trees: A A / \ / \ B C B C / \ D E but I am getting: A | A B | | B D | | C C Am I missing something or there is no way to do it? BTW, if I omit the label on my root node, I get a PGF error: ! Package pgf Error: No shape named is known. -- Tsf

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  • Visual C++ 2010 solution-wide macros with parameters

    - by OregonGhost
    I'm trying to compile some source code with Visual C++ 2010 Express. The code was written for GCC, and contains attributes like this: struct something { ... } __attribute__((packed)); Since this is not standard C++ syntax, Visual C++ doesn't recognize it. With this macro prior to the struct declaration, it works fine: #define __attribute__(p) But I don't want to alter the files. I created a new property sheet (GccCompat), and went to Preprocessor Definitions, and added the macro, like this: __attribute__(p) or like this: __attribute__(p)= But it doesn't work. It's simply not called. If I define just __attribute__ (without parameters) in the same location, the macro is correctly defined. Note that the command line that is generated looks fine (the macros with parameters are passed exactly the same as the ones without), but the compiler seems to ignore it. So, how can I globally define my macro with a parameter?

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  • Manipulating the case of the build macros in Visual Studio: $(TargetDir)

    - by miked
    I've come across a weird problem today in Visual Studio 2005. If I create a new configuration "NewConfiguration" for one of my projects. The output directory referred to by the project in $(TargetDir) is "/path/to/build/area/newconfiguration". Note the loss of capital letters, I'd expect it to be in "/path/to/build/area/NewConfiguration". In another project that I created yesterday, the capital letters are there. Normally this would be a problem, but it's part of a fairly complicated build system where some of it's on unix and we need to worry about case sensitive filename. Does anyone know where the source string for the Visual Studio macros like $(TargetDir) are stored so that I can get the case to be consistent and match what we need for our build system?

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  • Behavior with primitive data types' value out of range & C99's PRI* macros

    - by Yktula
    Say we have an 8-bit unsigned integer n (UINT8_MAX=255); what is the behavior of the compiler for n=256? Where can I find a table of default behavior when the value of a data type is out of range for different data types? Is there a pattern to how they behave when set out of range? #include <stdio.h> #include <inttypes.h> uint8_t n = UINT8_MAX; int main() { printf("%hhu ",n++); printf("%hhu",n); return 0; } Compiling with gcc -std=c99 -Wall *.c, this prints: 255 0 Also, is it acceptable to use C99's PRI* macros? How are they named?

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  • Dynamically create labels in gas macros?

    - by pgod
    Hi everyone, I would like to dynamically create a set of labels in an assembly function using a gas macro. I would like to do something like this: .macro set_up_jumptab_entry prefix, from=0, to=10 .quad \prefix_\item .if \to-\from set_up_jumptab_entry \prefix,"(\from+1)",\to .endif .endm set_up_jumptab_entry myfunc 0 10 Here \prefix_\item would be something like myfunction_7. Now, I can find lots of examples of recursive invocation, but I haven't found one of just label concatenation involving passed-in macro arguments. Gas is quite poorly documented, so answering this question is difficult for me. Can you concatenate arguments to macros with other tokens to make single tokens? What's your favorite gas assembler reference?

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  • c++ macros with memory?

    - by anon
    Is it possible to define macros write_foo(A); and read_foo(); so that: WRITE_FOO(hello); code_block_1; READ_FOO(); code_block_2; READ_FOO(); WRITE_FOO(world); code_block_3; READ_FOO(); code_block_4; READ_FOO(); expands into: code_block_1; hello; code_block_2; hello; code_boock_3; world; code_block_4; world; ? Thanks!

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  • What is "Call By Name"?

    - by forellana
    Hi to everyone! I'm working in a homework, and the professor asked me to implement the evaluation strategy called "call by name" in scheme in a certain language that we developed and he gave us an example at http://www.scala-lang.org/node/138 in the scala language, but i don't understand in what consists the call by name evaluation strategy? what differences it has with call by need? thanks, greetings

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  • Resources for learning Monads, Functors, Monoids, Arrows etc

    - by Dony Borris
    Can you people please suggest some good books / weblinks from where I can get to learn about above mentioned concepts? (Please note that I am a Java programmer and have NO prior experience with functional programming. I have been studying Scala since last one month and would appreciate the resources that try to teach the above mentioned concepts with Scala. (or even Java, if posible))

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  • How Do I Convert Pipe Delimited to Comma Delimited with Escaping

    - by Russ Bradberry
    Hi, I am fairly new to scala and I have the need to convert a string that is pipe delimited to one that is comma delimited, with the values wrapped in quotes and any quotes escaped by "\" in c# i would probably do this like this string st = "\"" + oldStr.Replace("\"", "\\\\\"").Replace("|", "\",\"") + "\"" I haven't validated that actually works but that is the basic idea behind what I am trying to do. Is there a way to do this easily in scala?

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  • Should I upgrade to Intellij Ultimate Edition?

    - by Benjamin Metz
    I am working in java and primarily Scala. I'm using the community edition of Intellij. I'm curious if its worth it to upgrade to the Ultimate Edition? I've been back and forth with Intellij and Eclipse... and for Scala dev I like Intellij a little bit better (for now). Thanks in advance...

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  • Is Odersky serious with "bills !*&^%~ code!" ?

    - by stacker
    In his book programming in scala (Chapter 5 Section 5.9 Pg 93) Odersky mentioned this expression "bills !*&^%~ code! In the footnote on same page: "By now you should be able to figure out that given this code,the Scala compiler would invoke (bills.!*&^%~(code)).!()." That's a bit to cryptic for me, could someone explain what's going on here?

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