Search Results

Search found 8749 results on 350 pages for 'nullable types'.

Page 77/350 | < Previous Page | 73 74 75 76 77 78 79 80 81 82 83 84  | Next Page >

  • Using LINQ to map dynamically (or construct projections)

    - by CodeGrue
    I know I can map two object types with LINQ using a projection as so: var destModel = from m in sourceModel select new DestModelType {A = m.A, C = m.C, E = m.E} where class SourceModelType { string A {get; set;} string B {get; set;} string C {get; set;} string D {get; set;} string E {get; set;} } class DestModelType { string A {get; set;} string C {get; set;} string E {get; set;} } But what if I want to make something like a generic to do this, where I don't know specifically the two types I am dealing with. So it would walk the "Dest" type and match with the matching "Source" types.. is this possible? Also, to achieve deferred execution, I would want it just to return an IQueryable. For example: public IQueryable<TDest> ProjectionMap<TSource, TDest>(IQueryable<TSource> sourceModel) { // dynamically build the LINQ projection based on the properties in TDest // return the IQueryable containing the constructed projection } I know this is challenging, but I hope not impossible, because it will save me a bunch of explicit mapping work between models and viewmodels.

    Read the article

  • Would making plain int 64-bit break a lot of reasonable code?

    - by R..
    Until recently, I'd considered the decision by most systems implementors/vendors to keep plain int 32-bit even on 64-bit machines a sort of expedient wart. With modern C99 fixed-size types (int32_t and uint32_t, etc.) the need for there to be a standard integer type of each size 8, 16, 32, and 64 mostly disappears, and it seems like int could just as well be made 64-bit. However, the biggest real consequence of the size of plain int in C comes from the fact that C essentially does not have arithmetic on smaller-than-int types. In particular, if int is larger than 32-bit, the result of any arithmetic on uint32_t values has type signed int, which is rather unsettling. Is this a good reason to keep int permanently fixed at 32-bit on real-world implementations? I'm leaning towards saying yes. It seems to me like there could be a huge class of uses of uint32_t which break when int is larger than 32 bits. Even applying the unary minus or bitwise complement operator becomes dangerous unless you cast back to uint32_t. Of course the same issues apply to uint16_t and uint8_t on current implementations, but everyone seems to be aware of and used to treating them as "smaller-than-int" types.

    Read the article

  • MVC2 Modelbinder for List of derived objects

    - by user250773
    I want a list of different (derived) object types working with the Default Modelbinder in Asp.net MVC 2. I have the following ViewModel: public class ItemFormModel { [Required(ErrorMessage = "Required Field")] public string Name { get; set; } public string Description { get; set; } [ScaffoldColumn(true)] //public List<Core.Object> Objects { get; set; } public ArrayList Objects { get; set; } } And the list contains objects of diffent derived types, e.g. public class TextObject : Core.Object { public string Text { get; set; } } public class BoolObject : Core.Object { public bool Value { get; set; } } It doesn't matter if I use the List or the ArrayList implementation, everything get's nicely scaffolded in the form, but the modelbinder doesn't resolve the derived object type properties for me when posting back to the ActionResult. What could be a good solution for the Viewmodel structure to get a list of different object types handled? Having an extra list for every object type (e.g. List, List etc.) seems to be not a good solution for me, since this is a lot of overhead both in building the viewmodel and mapping it back to the domain model. Thinking about the other approach of binding all properties in a custom model binder, how can I make use the data annotations approach here (validating required attributes etc.) without a lot of overhead?

    Read the article

  • C# Generics Question

    - by TheCloudlessSky
    Would it be possible to do something like the following in c#? Basically TParent and TChildren should be types of the class A but not necessairly have the same types that were passed in. I know this may sound confusing but I want to strongly type the children and parents of a particular object, but at the same time they must be of the same type. Because TParent inherits from A this would imply that it requires type parameters that inherit from A but using potentially different types. public class A<TParent, TChildren> where TParent : A where TControls : A { TParent Parent; List<TChildren> Children; } or more easily seen here: public class A<TParent, TChildren> where TParent : A<?, ?> where TChildren : A<?, ?> { TParent Parent; List<TChildren> Children; } I hope this isn't too confusing. Is this at all possible? Thanks :)

    Read the article

  • Type classe, generic memoization

    - by nicolas
    Something quite odd is happening with y types and I quite dont understand if this is justified or not. I would tend to think not. This code works fine : type DictionarySingleton private () = static let mutable instance = Dictionary<string*obj, obj>() static member Instance = instance let memoize (f:'a -> 'b) = fun (x:'a) -> let key = f.ToString(), (x :> obj) if (DictionarySingleton.Instance).ContainsKey(key) then let r = (DictionarySingleton.Instance).[key] r :?> 'b else let res = f x (DictionarySingleton.Instance).[key] <- (res :> obj) res And this ones complains type DictionarySingleton private () = static let mutable instance = Dictionary<string*obj, _>() static member Instance = instance let memoize (f:'a -> 'b) = fun (x:'a) -> let key = f.ToString(), (x :> obj) if (DictionarySingleton.Instance).ContainsKey(key) then let r = (DictionarySingleton.Instance).[key] r :?> 'b else let res = f x (DictionarySingleton.Instance).[key] <- (res :> obj) res The difference is only the underscore in the dictionary definition. The infered types are the same, but the dynamic cast from r to type 'b exhibits an error. 'this runtime coercition ... runtime type tests are not allowed on some types, etc..' Am I missing something or is it a rough edge ?

    Read the article

  • How to encapsulate a third party complex object structure?

    - by tangens
    Motivation Currently I'm using the java parser japa to create an abstract syntax tree (AST) of a java file. With this AST I'm doing some code generation (e.g.: if there's an annotation on a method, create some other source files, ...) Problem When my code generation becomes more complex, I've to dive deeper into the structure of the AST (e.g. I have to use visitors to extract some type information of method parameters). But I'm not sure if I want to stay with japa or if I will change the parser library later. Because my code generator uses freemarker (which isn't good at automatic refactoring) I want the interface that it uses to access the AST information to be stable, even if I decide to change the java parser. Question What's the best way to encapsulate complex datastructures of third party libraries? I could create my own datatypes and copy the parts of the AST that I need into these. I could create lots of specialized access methods that work with the AST and create exactly the infos I need (e.g. the fully qualified return type of a method as one string, or the first template parameter of a class). I could create wrapper classes for the japa datastructures I currently need and embed the japa types inside, so that I can delegate requests to the japa types and transform the resulting japa types to my wrapper classes again. Which solution should I take? Are there other (better) solutions to this problem?

    Read the article

  • Syntax for documenting JSON structure

    - by Roman A. Taycher
    So I'm trying to document the format of the json returned by an api I am writing against and I'd like to know if there is any popular format for the documentation of json structure. Note I'm not trying to to test or validate anything, I'm just using this for documentation. Also some ways to add comments to non-constants(items always returned w/ the same value) would be nice. This the not totally thought out scheme I'm currently using: Plain names refer to identifiers or types. Some types have type-comment Strings that appear to be constant(always returned for that type of request) strings are "str" Constant Numbers would be just the number Constant null is null Booleans are true/false for constant booleans or Boolean otherwise [a,b,c] are lists with 3 items a,b,c [... ...] is a list of repeating elements of some types/constants/patterns {a:A,b:B,c:c} and {... ...} is the same for a dictionary. example: story := [header,footer] header := {"data":realHeader,"kind":"Listing"} realHeader := {"after": null, "before": null, "children": [{"data": realRealHeader, "kind": "t3"}], "modhash": ""} footer := {"data":AlmostComments,"kind":"Listing"} AlmostComments := {"data": {"after": null, "before": null, "children": comments, "modhash": ""}, "kind": "t1"} comments := [...{"data":comment, "kind":"t1"}...] realRealHeader := {"author": string, "clicked": boolean, "created": int, "created_utc": int, "domain": "code.reddit.com", "downs": int, "hidden": boolean, "id": string-id, "is_self": boolean, "levenshtein": null, "likes": null, "media": null, "media_embed": { }, "name": string-id, "num_comments": int, "over_18": false, "permalink": string-urlLinkToStoryStartingFrom/r, "saved": false, "score": int, "selftext": string, "selftext_html": string-html, "subreddit": string-subredditname, "subreddit_id": string-id, "thumbnail": "", "title": string, "ups": int, "url": "http://code.reddit.com/" } comments := { "author": string, "body": string-body_html-wout-html, "body_html": string-html-formated, "created": int, "created_utc": int, "downs": int, "id": string-id, "levenshtein": null, "likes": null, "link_id": string-id, "name": string-id", "parent_id": string-id, "replies": AlmostComments or null, "subreddit": string-subredditname, "subreddit_id": string-id, "ups": int }

    Read the article

  • Callback function and function pointer trouble in C++ for a BST

    - by Brendon C.
    I have to create a binary search tree which is templated and can deal with any data types, including abstract data types like objects. Since it is unknown what types of data an object might have and which data is going to be compared, the client side must create a comparison function and also a print function (because also not sure which data has to be printed). I have edited some C code which I was directed to and tried to template, but I cannot figure out how to configure the client display function. I suspect variable 'tree_node' of class BinarySearchTree has to be passed in, but I am not sure how to do this. For this program I'm creating an integer binary search tree and reading data from a file. Any help on the code or the problem would be greatly appreciated :) Main.cpp #include "BinarySearchTreeTemplated.h" #include <iostream> #include <fstream> #include <string> using namespace std; /*Comparison function*/ int cmp_fn(void *data1, void *data2) { if (*((int*)data1) > *((int*)data2)) return 1; else if (*((int*)data1) < *((int*)data2)) return -1; else return 0; } static void displayNode() //<--------NEED HELP HERE { if (node) cout << " " << *((int)node->data) } int main() { ifstream infile("rinput.txt"); BinarySearchTree<int> tree; while (true) { int tmp1; infile >> tmp1; if (infile.eof()) break; tree.insertRoot(tmp1); } return 0; } BinarySearchTree.h (a bit too big to format here) http://pastebin.com/4kSVrPhm

    Read the article

  • What are the default return values for operator< and operator[] in C++ (Visual Studio 6)?

    - by DustOff
    I've inherited a large Visual Studio 6 C++ project that needs to be translated for VS2005. Some of the classes defined operator< and operator[], but don't specify return types in the declarations. VS6 allows this, but not VS2005. I am aware that the C standard specifies that the default return type for normal functions is int, and I assumed VS6 might have been following that, but would this apply to C++ operators as well? Or could VS6 figure out the return type on its own? For example, the code defines a custom string class like this: class String { char arr[16]; public: operator<(const String& other) { return something1 < something2; } operator[](int index) { return arr[index]; } }; Would VS6 have simply put the return types for both as int, or would it have been smart enough to figure out that operator[] should return a char and operator< should return a bool (and not convert both results to int all the time)? Of course I have to add return types to make this code VS2005 C++ compliant, but I want to make sure to specify the same type as before, as to not immediately change program behavior (we're going for compatibility at the moment; we'll standardize things later).

    Read the article

  • Porting Symbian C++ to Android NDK

    - by Donal Rafferty
    I've been given some Symbian C++ code to port over for use with the Android NDK. The code has lots of Symbian specific code in it and I have very little experience of C++ so its not going very well. The main thing that is slowing me down is trying to figure out the alternatives to use in normal C++ for the Symbian specific code. At the minute the compiler is throwing out all sorts of errors for unrecognised types. From my recent research these are the types that I believe are Symbian specific: TInt, TBool, TDesc8, RSocket, TInetAddress, TBuf, HBufc, RPointerArray Changing TInt and TBool to int and bool respectively works in the compiler but I am unsure what to use for the other types? Can anyone help me out with them? Especially TDesc, TBuf, HBuf. Also Symbian has a two phase contructor using NewL and NewLc But would changing this to a normal C++ constructor be ok? Finally Symbian uses the clean up stack to help eliminate memory leaks I believe, would removing the clean up stack code be acceptable, I presume it should be replaced with try/catch statements?

    Read the article

  • How to alter Postgres table data based on its contents?

    - by williamjones
    This is probably a super simple question, but I'm struggling to come up with the right keywords to find it on Google. I have a Postgres table that has among its contents a column of type text named content_type. That stores what type of entry is stored in that row. There are only about 5 different types, and I decided I want to change one of them to display as something else in my application (I had been directly displaying these). It struck me that it's funny that my view is being dictated by my database model, and I decided I would convert the types being stored in my database as strings into integers, and enumerate the possible types in my application with constants that convert them into their display names. That way, if I ever got the urge to change any category names again, I could just change it with one alteration of a constant. I also have the hunch that storing integers might be somewhat more efficient than storing text in the database. First, a quick threshold question of, is this a good idea? Any feedback or anything I missed? Second, and my main question, what's the Postgres command I could enter to make an alteration like this? I'm thinking I could start by renaming the old content_type column to old_content_type and then creating a new integer column content_type. However, what command would look at a row's old_content_type and fill in the new content_type column based off of that?

    Read the article

  • An array problem in C++

    - by manugupt1
    To access the array indice at the xth position we can use some sort of illustration as shown below #include<iostream> using namespace std; int main(){ float i[20]; for(int j=0;j<=20;j++) i[j]=0; } However the following piece of code does not work #include<iostream> using namespace std; float oldrand[55]; int jrand; void advance_random(){ int j1; float new_random; for(j1=0;j1<=23;j1++){ int temp = j1+30; new_random = (oldrand[j1]) - (oldrand[temp]); if(new_random <0.0) new_random = new_random+1; oldrand[j1] = new_random; } for(j1=24;j1<=54;j1++){ new_random[j1] = oldrand[j1] - oldrand[j1-23]; if(new_random[j1]<0.0) new_random[j1] = new_random + 1; oldrand[j1]=new_random; } } I recieve the following error ga.cpp:20: error: invalid types ‘float[int]’ for array subscript ga.cpp:21: error: invalid types ‘float[int]’ for array subscript ga.cpp:22: error: invalid types ‘float[int]’ for array subscript I am not able to find a mistake in my code please help me

    Read the article

  • Faster Insertion of Records into a Table with SQLAlchemy

    - by Kyle Brandt
    I am parsing a log and inserting it into either MySQL or SQLite using SQLAlchemy and Python. Right now I open a connection to the DB, and as I loop over each line, I insert it after it is parsed (This is just one big table right now, not very experienced with SQL). I then close the connection when the loop is done. The summarized code is: log_table = schema.Table('log_table', metadata, schema.Column('id', types.Integer, primary_key=True), schema.Column('time', types.DateTime), schema.Column('ip', types.String(length=15)) .... engine = create_engine(...) metadata.bind = engine connection = engine.connect() .... for line in file_to_parse: m = line_regex.match(line) if m: fields = m.groupdict() pythonified = pythoninfy_log(fields) #Turn them into ints, datatimes, etc if use_sql: ins = log_table.insert(values=pythonified) connection.execute(ins) parsed += 1 My two questions are: Is there a way to speed up the inserts within this basic framework? Maybe have a Queue of inserts and some insertion threads, some sort of bulk inserts, etc? When I used MySQL, for about ~1.2 million records the insert time was 15 minutes. With SQLite, the insert time was a little over an hour. Does that time difference between the db engines seem about right, or does it mean I am doing something very wrong?

    Read the article

  • I have a bunch of template parameters that I want to hide from my users. How can I do this?

    - by Alex
    I have a superclass which is defined in terms of a few internal types it uses. Subclassing is performed as so: template <class InternalType1, class InternalType2> class Super { ... } class Sub : Super <interalTypeClass1, interalTypeClass2> { ... } But when I want to write a function that takes a pointer to the superclass, this happens : template <class InternalType1, class InternalType2> void function(Super<InternalType1, InternalType2>* in) { ... } The user really shouldn't know anything about the inside classes, and should really just concern himself with the use of the function. Some of these template lists become very very large, and expecting the user to pass them every time is wasteful, in my opinion. Any suggestions? EDIT: The function needs to know the internal types in use, so unless there is a way to access template types at compile time, I think there is no solution? Potential solution: Have each class do the following: #define SubTemplateArgs <SubTypeName, SubInternalType1, SubInternalType2> ?

    Read the article

  • importing symbols from python package into caller's namespace

    - by Paul C
    I have a little internal DSL written in a single Python file that has grown to a point where I would like to split the contents across a number of different directories + files. The new directory structure currently looks like this: dsl/ __init__.py types/ __init__.py type1.py type2.py and each type file contains a class (e.g. Type1). My problem is that I would like to keep the implementation of code that uses this DSL as simple as possible, something like: import dsl x = Type1() ... This means that all of the important symbols should be available directly in the user's namespace. I have tried updating the top-level __init__.py file to import the relevant symbols: from types.type1 import Type1 from types.type2 import Type2 ... print globals() the output shows that the symbols are imported correctly, but they still aren't present in the caller's code (the code that's doing the import dsl). I think that the problem is that the symbols are actually being imported to the 'dsl' namespace. How can I change this so that the classes are also directly available in the caller's namespace?

    Read the article

  • When to use reinterpret_cast?

    - by HeretoLearn
    I am little confused with the applicability of reinterpret_cast vs static_cast. From what I have read the general rules are to use static cast when the types can be interpreted at compile time hence the word static. This is the cast the C++ compiler uses internally for implicit casts also. reinterpret_cast are applicable in two scenarios, convert integer types to pointer types and vice versa or to convert one pointer type to another. The general idea I get is this is unportable and should be avoided. Where I am a little confused is one usage which I need, I am calling C++ from C and the C code needs to hold on to the C++ object so basically it holds a void*. What cast should be used to convert between the void * and the Class type? I have seen usage of both static_cast and reinterpret_cast? Though from what I have been reading it appears static is better as the cast can happen at compile time? Though it says to use reinterpret_cast to convert from one pointer type to another?

    Read the article

  • Type-safe generic data structures in plain-old C?

    - by Bradford Larsen
    I have done far more C++ programming than "plain old C" programming. One thing I sorely miss when programming in plain C is type-safe generic data structures, which are provided in C++ via templates. For sake of concreteness, consider a generic singly linked list. In C++, it is a simple matter to define your own template class, and then instantiate it for the types you need. In C, I can think of a few ways of implementing a generic singly linked list: Write the linked list type(s) and supporting procedures once, using void pointers to go around the type system. Write preprocessor macros taking the necessary type names, etc, to generate a type-specific version of the data structure and supporting procedures. Use a more sophisticated, stand-alone tool to generate the code for the types you need. I don't like option 1, as it is subverts the type system, and would likely have worse performance than a specialized type-specific implementation. Using a uniform representation of the data structure for all types, and casting to/from void pointers, so far as I can see, necessitates an indirection that would be avoided by an implementation specialized for the element type. Option 2 doesn't require any extra tools, but it feels somewhat clunky, and could give bad compiler errors when used improperly. Option 3 could give better compiler error messages than option 2, as the specialized data structure code would reside in expanded form that could be opened in an editor and inspected by the programmer (as opposed to code generated by preprocessor macros). However, this option is the most heavyweight, a sort of "poor-man's templates". I have used this approach before, using a simple sed script to specialize a "templated" version of some C code. I would like to program my future "low-level" projects in C rather than C++, but have been frightened by the thought of rewriting common data structures for each specific type. What experience do people have with this issue? Are there good libraries of generic data structures and algorithms in C that do not go with Option 1 (i.e. casting to and from void pointers, which sacrifices type safety and adds a level of indirection)?

    Read the article

  • Make conversion to a native type explicit in C++

    - by Tal Pressman
    I'm trying to write a class that implements 64-bit ints for a compiler that doesn't support long long, to be used in existing code. Basically, I should be able to have a typedef somewhere that selects whether I want to use long long or my class, and everything else should compile and work. So, I obviously need conversion constructors from int, long, etc., and the respective conversion operators (casts) to those types. This seems to cause errors with arithmetic operators. With native types, the compiler "knows" that when operator*(int, char) is called, it should promote the char to int and call operator*(int, int) (rather than casting the int to char, for example). In my case it gets confused between the various built-in operators and the ones I created. It seems to me like if I could flag the conversion operators as explicit somehow, that it would solve the issue, but as far as I can tell the explicit keyword is only for constructors (and I can't make constructors for built-in types). So is there any way of marking the casts as explicit? Or am I barking up the wrong tree here and there's another way of solving this? Or maybe I'm just doing something else wrong...

    Read the article

  • Linq-to-sql join/where?

    - by Curtis White
    I've the following table structures Users id Types id isBool UsersTypes userid types I want to select all the UserTypes based on id and isBool. I tried this query var q = from usertype in usertypes from type in types where type.isBool == false where userstypes.user == id select usertype; But this did not work as expected. My questions are: Why? Is there any difference in using the join on syntax vs where, where vs where cond1 && cond2? My understanding is query optimizer will optimize. Is there any difference in using where cond1 == var1 && cond2 == var2 with and without the parenthesis? This seems peculiar that it is possible to build this without parenthesis What type of query do I need in this case? I can see that I could do a subquery or use a group but not 100% sure if it is required. An example might be helpful. I'm thinking a subquery may be required in this case.

    Read the article

  • Wordpress and Dynamic Programming Php

    - by user1675146
    I have geography pages for two types of business listings. Each page goes from state, county, city, but I need to have the same geography shared between two types of business. My two business types are dentist and chiropractors. I am trying to have a permalink structure like this: enter code here xyz.com/dentist/alabama enter code here xyz.com/dentist/alabama/polk-county/ enter code here xyz.com/chiropractors/alabama/ enter code here xyz.com/chiropractors/alabama/polk-county/ I originally was going to load the geography as pages and subpages, but with that method I cannot get the permalink separated by the type chiropractor and dentist. So now I have created a custom post type one for chiropractor and one for dentist which give me the permalink xyz.com/dentist and xyz.com/chiropractor. My question is now how to handle my category geography page. I was wondering if in wordpress it is possible to create a shell page such as xyz.com/dentist/[state]/ and then through php dynamically build a page for each state? So where it shows [state] it will be replaced with the actual state such as alabama, california etc when that specific page is viewed. But the shell page is just 1 page in the database. If so could someone give me a basic explanation on how to instruct a programmer to do this? Thank you.

    Read the article

  • How can you use Windows Backup with a TrueCrypt encrypted backup destination?

    - by Burly
    Background There are numerous backup solutions out there for Windows and they come in many different forms. From a file copy and/or syncing tool like SyncBackSE to whole hard drive backup utilities based on Volume Shadow Copy like Acronis TrueImage or Norton Ghost to block level copy tools like dd. Each of these solutions offers different pros and cons versus the "Windows Backup and Restore Center" feature built-in to Windows Vista and Windows 7. I am not interested in discussing alternative backup solutions here however, as that has already been covered by numerous other questions. Contraints There are two "types" of backup supported by the "Windows Backup and Restore Center"(WBRC): - File backup (which Windows calls "Back Up Files") - Full System Backup (which Windows calls "Complete PC Backup) I am interested in a solution which supports either and/or both types of backup with WBRC. Questions How can you use a TrueCrypt encrypted mount point as the destination for the built-in "Windows Backup and Restore Center" feature in Windows Vista and 7? See-Also Volume Shadow Copy based backup that works with TrueCrypt References Backup and Restore Center Windows Vista - Backup and Restore Center Windows 7 - Backup and Restore Center

    Read the article

  • How to type multiple characters on a mac with a single click?

    - by Yuval
    On a Windows machine, clicking and holding a keyboard key results in the key being types multiple times. For example, if I click and hold 'q' for a few seconds, I end up with the following: qqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqq Similarly, I can click and hold the Backspace key to delete multiple characters. On a Mac, it seems, clicking and holding a key for several seconds results in the key being types only once. To type it repeatedly, it is necessary to psychically click it multiple times. I'm unclear about whether that is a bug or a supposed-feature, but I am interested in replicating this functionality on a Mac. Any ideas? Thanks!

    Read the article

  • The Koyal Group Info Mag News¦Charged building material could make the renewable grid a reality

    - by Chyler Tilton
    What if your cell phone didn’t come with a battery? Imagine, instead, if the material from which your phone was built was a battery. The promise of strong load-bearing materials that can also work as batteries represents something of a holy grail for engineers. And in a letter published online in Nano Letters last week, a team of researchers from Vanderbilt University describes what it says is a breakthrough in turning that dream into an electrocharged reality. The researchers etched nanopores into silicon layers, which were infused with a polyethylene oxide-ionic liquid composite and coated with an atomically thin layer of carbon. In doing so, they created small but strong supercapacitor battery systems, which stored electricity in a solid electrolyte, instead of using corrosive chemical liquids found in traditional batteries. These supercapacitors could store and release about 98 percent of the energy that was used to charge them, and they held onto their charges even as they were squashed and stretched at pressures up to 44 pounds per square inch. Small pieces of them were even strong enough to hang a laptop from—a big, fat Dell, no less. Although the supercapacitors resemble small charcoal wafers, they could theoretically be molded into just about any shape, including a cell phone’s casing or the chassis of a sedan. They could also be charged—and evacuated of their charge—in less time than is the case for traditional batteries. “We’ve demonstrated, for the first time, the simple proof-of-concept that this can be done,” says Cary Pint, an assistant professor in the university’s mechanical engineering department and one of the authors of the new paper. “Now we can extend this to all kinds of different materials systems to make practical composites with materials specifically tailored to a host of different types of applications. We see this as being just the tip of a very massive iceberg.” Pint says potential applications for such materials would go well beyond “neat tech gadgets,” eventually becoming a “transformational technology” in everything from rocket ships to sedans to home building materials. “These types of systems could range in size from electric powered aircraft all the way down to little tiny flying robots, where adding an extra on-board battery inhibits the potential capability of the system,” Pint says. And they could help the world shift to the intermittencies of renewable energy power grids, where powerful batteries are needed to help keep the lights on when the sun is down or when the wind is not blowing. “Using the materials that make up a home as the native platform for energy storage to complement intermittent resources could also open the door to improve the prospects for solar energy on the U.S. grid,” Pint says. “I personally believe that these types of multifunctional materials are critical to a sustainable electric grid system that integrates solar energy as a key power source.”

    Read the article

  • dev_install failed on ARM chromebook

    - by user1027721
    I'm trying this guide for having access to emerge on chromeos. http://www.chromium.org/chromium-os/how-tos-and-troubleshooting/install-software-on-base-images Unfortunately I always got the same error which is $ sudo dev_install Starting installation of developer packages. First, we download the necessary files. Downloading https://commondatastorage.googleapis.com/chromeos-dev-installer/board/daisy/full-3.168.0.0/packages/app-misc/mime-types-8.tbz2 % Total % Received % Xferd Average Speed Time Time Time Current Dload Upload Total Spent Left Speed 100 127 100 127 0 0 252 0 --:--:-- --:--:-- --:--:-- 305 [: 184: -ne: unexpected operator Extracting /usr/local/portage/packages/app-misc/mime-types-8.tbz2 I think that it somehow returns a 404 everytime. Thanks for your help

    Read the article

  • Upgrading Redmine, activerecord-mysql2-adapter not recognized

    - by David Kaczynski
    For upgrading Redmine from 1.0.1 to 2.1.2, I need to execute the command: rake db:migrate RAILS_ENV=production However, doing so produces the following error: rake aborted! Please install the mysql2 adapter: gem install activerecord-mysql2-adapter (mysql2 is not part of the bundle. Add it to Gemfile.) I have ran gem install activerecord-mysql2-adapter, but I still get the same error when I try to run the rake ... command. How do I get my RoR app to recognize that I have the mysql2 adapter installed already? or Is there something wrong with my activerecord-mysql2-adapter installation? Results of sudo bundle install: Using rake (10.0.0) Using i18n (0.6.1) Using multi_json (1.3.7) Using activesupport (3.2.8) Using builder (3.0.0) Using activemodel (3.2.8) Using erubis (2.7.0) Using journey (1.0.4) Using rack (1.4.1) Using rack-cache (1.2) Using rack-test (0.6.2) Using hike (1.2.1) Using tilt (1.3.3) Using sprockets (2.1.3) Using actionpack (3.2.8) Using mime-types (1.19) Using polyglot (0.3.3) Using treetop (1.4.12) Using mail (2.4.4) Using actionmailer (3.2.8) Using arel (3.0.2) Using tzinfo (0.3.35) Using activerecord (3.2.8) Using activeresource (3.2.8) Using coderay (1.0.8) Using fastercsv (1.5.5) Using rack-ssl (1.3.2) Using json (1.7.5) Using rdoc (3.12) Using thor (0.16.0) Using railties (3.2.8) Using jquery-rails (2.0.3) Using metaclass (0.0.1) Using mocha (0.12.3) Using mysql (2.8.1) Using net-ldap (0.3.1) Using pg (0.14.1) Using ruby-openid (2.1.8) Using rack-openid (1.3.1) Using bundler (1.2.1) Using rails (3.2.8) Using rmagick (2.13.1) Using shoulda (2.11.3) Using sqlite3 (1.3.6) Using yard (0.8.3) [32mYour bundle is complete! Use `bundle show [gemname]` to see where a bundled gem is installed.[0m Results of sudo find / -name "*mysql2*": /var/lib/gems/1.8/doc/mysql2-0.3.11 /var/lib/gems/1.8/doc/activerecord-3.2.9/ri/ActiveRecord/Base/mysql2_connection-c.ri /var/lib/gems/1.8/doc/activerecord-mysql2-adapter-0.0.3 /var/lib/gems/1.8/doc/activerecord-mysql2-adapter-0.0.3/ri/ActiveRecord/Base/em_mysql2_connection-c.ri /var/lib/gems/1.8/doc/activerecord-mysql2-adapter-0.0.3/ri/ActiveRecord/Base/mysql2_connection-c.ri /var/lib/gems/1.8/gems/mysql2-0.3.11 /var/lib/gems/1.8/gems/mysql2-0.3.11/spec/mysql2 /var/lib/gems/1.8/gems/mysql2-0.3.11/mysql2.gemspec /var/lib/gems/1.8/gems/mysql2-0.3.11/lib/mysql2.rb /var/lib/gems/1.8/gems/mysql2-0.3.11/lib/mysql2 /var/lib/gems/1.8/gems/mysql2-0.3.11/lib/mysql2/mysql2.so /var/lib/gems/1.8/gems/mysql2-0.3.11/ext/mysql2 /var/lib/gems/1.8/gems/mysql2-0.3.11/ext/mysql2/mysql2.so /var/lib/gems/1.8/gems/mysql2-0.3.11/ext/mysql2/mysql2_ext.c /var/lib/gems/1.8/gems/mysql2-0.3.11/ext/mysql2/mysql2_ext.h /var/lib/gems/1.8/gems/mysql2-0.3.11/ext/mysql2/mysql2_ext.o /var/lib/gems/1.8/gems/activerecord-3.2.9/lib/active_record/connection_adapters/mysql2_adapter.rb /var/lib/gems/1.8/gems/activerecord-mysql2-adapter-0.0.3 /var/lib/gems/1.8/gems/activerecord-mysql2-adapter-0.0.3/activerecord-mysql2-adapter.gemspec /var/lib/gems/1.8/gems/activerecord-mysql2-adapter-0.0.3/lib/arel/engines/sql/compilers/mysql2_compiler.rb /var/lib/gems/1.8/gems/activerecord-mysql2-adapter-0.0.3/lib/activerecord-mysql2-adapter.rb /var/lib/gems/1.8/gems/activerecord-mysql2-adapter-0.0.3/lib/activerecord-mysql2-adapter /var/lib/gems/1.8/gems/activerecord-mysql2-adapter-0.0.3/lib/active_record/connection_adapters/em_mysql2_adapter.rb /var/lib/gems/1.8/gems/activerecord-mysql2-adapter-0.0.3/lib/active_record/connection_adapters/mysql2_adapter.rb /var/lib/gems/1.8/gems/activerecord-3.2.8/lib/active_record/connection_adapters/mysql2_adapter.rb /var/lib/gems/1.8/cache/mysql2-0.3.11.gem /var/lib/gems/1.8/cache/activerecord-mysql2-adapter-0.0.3.gem /var/lib/gems/1.8/specifications/activerecord-mysql2-adapter-0.0.3.gemspec /var/lib/gems/1.8/specifications/mysql2-0.3.11.gemspec Contents of /usr/share/redmine/Gemfile: source 'http://rubygems.org' gem 'rails', '3.2.8' gem "jquery-rails", "~> 2.0.2" gem "i18n", "~> 0.6.0" gem "coderay", "~> 1.0.6" gem "fastercsv", "~> 1.5.0", :platforms => [:mri_18, :mingw_18, :jruby] gem "builder", "3.0.0" # Optional gem for LDAP authentication group :ldap do gem "net-ldap", "~> 0.3.1" end # Optional gem for OpenID authentication group :openid do gem "ruby-openid", "~> 2.1.4", :require => "openid" gem "rack-openid" end # Optional gem for exporting the gantt to a PNG file, not supported with jruby platforms :mri, :mingw do group :rmagick do # RMagick 2 supports ruby 1.9 # RMagick 1 would be fine for ruby 1.8 but Bundler does not support # different requirements for the same gem on different platforms gem "rmagick", ">= 2.0.0" end end # Database gems platforms :mri, :mingw do group :postgresql do gem "pg", ">= 0.11.0" end group :sqlite do gem "sqlite3" end end platforms :mri_18, :mingw_18 do group :mysql do gem "mysql" end end platforms :mri_19, :mingw_19 do group :mysql do gem "mysql2", "~> 0.3.11" end end platforms :jruby do gem "jruby-openssl" group :mysql do gem "activerecord-jdbcmysql-adapter" end group :postgresql do gem "activerecord-jdbcpostgresql-adapter" end group :sqlite do gem "activerecord-jdbcsqlite3-adapter" end end group :development do gem "rdoc", ">= 2.4.2" gem "yard" end group :test do gem "shoulda", "~> 2.11" # Shoulda does not work nice on Ruby 1.9.3 and seems to need test-unit explicitely. gem "test-unit", :platforms => [:mri_19] gem "mocha", "0.12.3" end local_gemfile = File.join(File.dirname(__FILE__), "Gemfile.local") if File.exists?(local_gemfile) puts "Loading Gemfile.local ..." if $DEBUG # `ruby -d` or `bundle -v` instance_eval File.read(local_gemfile) end # Load plugins' Gemfiles Dir.glob File.expand_path("../plugins/*/Gemfile", __FILE__) do |file| puts "Loading #{file} ..." if $DEBUG # `ruby -d` or `bundle -v` instance_eval File.read(file) end Contents of /usr/share/redmine/Gemfile.lock: GEM remote: http://rubygems.org/ specs: actionmailer (3.2.8) actionpack (= 3.2.8) mail (~> 2.4.4) actionpack (3.2.8) activemodel (= 3.2.8) activesupport (= 3.2.8) builder (~> 3.0.0) erubis (~> 2.7.0) journey (~> 1.0.4) rack (~> 1.4.0) rack-cache (~> 1.2) rack-test (~> 0.6.1) sprockets (~> 2.1.3) activemodel (3.2.8) activesupport (= 3.2.8) builder (~> 3.0.0) activerecord (3.2.8) activemodel (= 3.2.8) activesupport (= 3.2.8) arel (~> 3.0.2) tzinfo (~> 0.3.29) activeresource (3.2.8) activemodel (= 3.2.8) activesupport (= 3.2.8) activesupport (3.2.8) i18n (~> 0.6) multi_json (~> 1.0) arel (3.0.2) builder (3.0.0) coderay (1.0.8) erubis (2.7.0) fastercsv (1.5.5) hike (1.2.1) i18n (0.6.1) journey (1.0.4) jquery-rails (2.0.3) railties (>= 3.1.0, < 5.0) thor (~> 0.14) json (1.7.5) mail (2.4.4) i18n (>= 0.4.0) mime-types (~> 1.16) treetop (~> 1.4.8) metaclass (0.0.1) mime-types (1.19) mocha (0.12.3) metaclass (~> 0.0.1) multi_json (1.3.7) mysql (2.8.1) mysql2 (0.3.11) net-ldap (0.3.1) pg (0.14.1) polyglot (0.3.3) rack (1.4.1) rack-cache (1.2) rack (>= 0.4) rack-openid (1.3.1) rack (>= 1.1.0) ruby-openid (>= 2.1.8) rack-ssl (1.3.2) rack rack-test (0.6.2) rack (>= 1.0) rails (3.2.8) actionmailer (= 3.2.8) actionpack (= 3.2.8) activerecord (= 3.2.8) activeresource (= 3.2.8) activesupport (= 3.2.8) bundler (~> 1.0) railties (= 3.2.8) railties (3.2.8) actionpack (= 3.2.8) activesupport (= 3.2.8) rack-ssl (~> 1.3.2) rake (>= 0.8.7) rdoc (~> 3.4) thor (>= 0.14.6, < 2.0) rake (10.0.0) rdoc (3.12) json (~> 1.4) rmagick (2.13.1) ruby-openid (2.1.8) shoulda (2.11.3) sprockets (2.1.3) hike (~> 1.2) rack (~> 1.0) tilt (~> 1.1, != 1.3.0) sqlite3 (1.3.6) test-unit (2.5.2) thor (0.16.0) tilt (1.3.3) treetop (1.4.12) polyglot polyglot (>= 0.3.1) tzinfo (0.3.35) yard (0.8.3) PLATFORMS ruby DEPENDENCIES activerecord-jdbcmysql-adapter activerecord-jdbcpostgresql-adapter activerecord-jdbcsqlite3-adapter builder (= 3.0.0) coderay (~> 1.0.6) fastercsv (~> 1.5.0) i18n (~> 0.6.0) jquery-rails (~> 2.0.2) jruby-openssl mocha (= 0.12.3) mysql mysql2 (~> 0.3.11) net-ldap (~> 0.3.1) pg (>= 0.11.0) rack-openid rails (= 3.2.8) rdoc (>= 2.4.2) rmagick (>= 2.0.0) ruby-openid (~> 2.1.4) shoulda (~> 2.11) sqlite3 test-unit yard Results of gem list: actionmailer (3.2.9, 3.2.8) actionpack (3.2.9, 3.2.8) activemodel (3.2.9, 3.2.8) activerecord (3.2.9, 3.2.8) activerecord-mysql2-adapter (0.0.3) activeresource (3.2.9, 3.2.8) activesupport (3.2.9, 3.2.8) arel (3.0.2) builder (3.0.0) bundler (1.2.1) coderay (1.0.8) erubis (2.7.0) fastercsv (1.5.5) hike (1.2.1) i18n (0.6.1) journey (1.0.4) jquery-rails (2.0.3) json (1.7.5) mail (2.4.4) metaclass (0.0.1) mime-types (1.19) mocha (0.12.3) multi_json (1.3.7) mysql (2.8.1) mysql2 (0.3.11) net-ldap (0.3.1) pg (0.14.1) polyglot (0.3.3) rack (1.4.1) rack-cache (1.2) rack-openid (1.3.1) rack-ssl (1.3.2) rack-test (0.6.2) rails (3.2.9, 3.2.8) railties (3.2.9, 3.2.8) rake (10.0.0) rdoc (3.12) rmagick (2.13.1) ruby-openid (2.1.8) shoulda (2.11.3) sprockets (2.2.1, 2.1.3) sqlite3 (1.3.6) thor (0.16.0) tilt (1.3.3) treetop (1.4.12) tzinfo (0.3.35) yard (0.8.3) Results of 'bundle show`: Gems included by the bundle: * actionmailer (3.2.8) * actionpack (3.2.8) * activemodel (3.2.8) * activerecord (3.2.8) * activeresource (3.2.8) * activesupport (3.2.8) * arel (3.0.2) * builder (3.0.0) * bundler (1.2.1) * coderay (1.0.8) * erubis (2.7.0) * fastercsv (1.5.5) * hike (1.2.1) * i18n (0.6.1) * journey (1.0.4) * jquery-rails (2.0.3) * json (1.7.5) * mail (2.4.4) * metaclass (0.0.1) * mime-types (1.19) * mocha (0.12.3) * multi_json (1.3.7) * mysql (2.8.1) * net-ldap (0.3.1) * pg (0.14.1) * polyglot (0.3.3) * rack (1.4.1) * rack-cache (1.2) * rack-openid (1.3.1) * rack-ssl (1.3.2) * rack-test (0.6.2) * rails (3.2.8) * railties (3.2.8) * rake (10.0.0) * rdoc (3.12) * rmagick (2.13.1) * ruby-openid (2.1.8) * shoulda (2.11.3) * sprockets (2.1.3) * sqlite3 (1.3.6) * thor (0.16.0) * tilt (1.3.3) * treetop (1.4.12) * tzinfo (0.3.35) * yard (0.8.3)

    Read the article

< Previous Page | 73 74 75 76 77 78 79 80 81 82 83 84  | Next Page >