traits | Observable typed attributes for Python classes
kandi X-RAY | traits Summary
kandi X-RAY | traits Summary
Observable typed attributes for Python classes
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Top functions reviewed by kandi - BETA
- Registers a trait listener
- Called when a trait changes
- Returns a list of trait names
- Get the values for the given attributes
- Define metadata
- Check if the given trait is actrait object
- Add an article
- Convert an object into a CTrait object
- Parse a listener
- Push a handler to the stack
- Parse sequence
- Convert to CTrait
- Adapt the given object to a given protocol
- Register a single trait
- Log exceptions raised by traits
- Decorator to cache a property
- Print a list of trait names
- Decorates a property based on a dependency
- Edit traits
- Configure traits from a file
- Create a trait
- Register a listener
- Apply the given expression
- Register a dictionary
- Add a trait
- Creates a decorator that takes an expression
traits Key Features
traits Examples and Code Snippets
Community Discussions
Trending Discussions on traits
QUESTION
#include
#include
struct Foo
{
// ### Member Function ###
void bar() { std::cout << "Foo::bar()\n"; }
};
// ### 1 Parameter Primary Template (which is empty) ###
template
struct Traits {};
// ### 2 Parameter Template Specialization ###
template
struct Traits
^^^^^^ // I don't understand this syntax
{
using type1 = T;
using type2 = U;
};
int main()
{
// ### Pointer to member function ###
void (Foo::*memFuncPtr)() = &Foo::bar;
Foo f;
// ### Use the member function pointer to invoke it ###
(f.*memFuncPtr)();
static_assert(std::is_same_v::type1>);
static_assert(std::is_same_v::type2>);
return 0;
}
ANSWER
Answered 2022-Apr-09 at 05:11QUESTION
I have the error stated above, and here is the copy log
...ANSWER
Answered 2021-Aug-01 at 00:51You need to use the factory trait for the model to have the factory() method available.
QUESTION
Let's say I have a variadic function template taking a function pointer to a function with said variadic arguments. The following code does not compile under gcc (11.2), but compiles under clang and msvc (https://godbolt.org/z/TWbEKWb9f).
...ANSWER
Answered 2022-Mar-29 at 21:41The cv-qualifier should always be dropped (both in determining the type of dummyFunc and when substituting the deduced argument into the callFunc signature), and I'm pretty sure all compilers agree on this. It's not really what the question is about. Let's change the example a bit:
QUESTION
The following code compiles fine:
...ANSWER
Answered 2022-Mar-22 at 17:52Consider if we implement Fn manually (of course this requires nightly)...
QUESTION
Haskell supports type classes, like equality:
...ANSWER
Answered 2022-Jan-30 at 20:59In Haskell, you can use existential types to express "some unknown type of this typeclass". (In older versions of GHC, you will need a few standard extensions on.)
QUESTION
Discussion about this was started under this answer for quite simple question.
ProblemThis simple code has unexpected overload resolution of constructor for std::basic_string:
ANSWER
Answered 2022-Jan-05 at 12:05Maybe I'm wrong, but it seems that last part:
QUESTION
A quote from the standard regarding std::basic_string_view equality comparison operators (see http://eel.is/c++draft/string.view#comparison):
...[Example 1: A sample conforming implementation for operator== would be:
ANSWER
Answered 2022-Jan-25 at 15:13I think this is insufficient reduction as a result of the adoption of <=> in P1614. Before that paper, there were three ==s in the example:
QUESTION
I would like to detect if a function (operator() in my case) is present in a class, regardless of its signature or whether it would be possible to get a pointer to it (may be impossible without additional info because it is templated or overloaded). The following code using a concept compiles on MSVC and clang, but not GCC (see godbolt link below for error messages). Is this supposed to work and is GCC not conformant, or is this not supposed to work and are MSVC and clang too lenient? It is interesting to note GCC fails not only for the overloaded and templated operator()s, but also for the simple functor.
Note also that while the example code uses variations on unary functions taking an int, I'd like the concept to work regardless of function signature (and its does for MSVC and clang).
Try here for GCC, clang and MSVC.
Context is making this work, it does now on MSVC and clang, but not GCC.
...ANSWER
Answered 2022-Jan-13 at 15:30First, the way to check a concept is just to static_assert (not to try to instantiate a constrained class template).
QUESTION
I learned an idiom to give an alias to trait. But, when I applied this idiom to my code, I encountered a puzzling error.
Here is a simplified version of the code:
...ANSWER
Answered 2022-Jan-10 at 05:12I have found a work-around for this problem in a GitHub discussion. First, we define a no-op function to help in the type inference of the closure.
QUESTION
I wrote a function to iterate over neighbors of cells in a 2d grid:
...ANSWER
Answered 2021-Dec-22 at 19:37If I understand correctly, returning an
implwould result in slower code, calling function pointers instead of compiling things down to simple loops. Right?
Nope. Returning impl Iterator is exactly the same, codegen-wise, as returning Map<...>>>.¹ The difference is twofold:
- Changing the return type of
neighboursdoes not require changing its signature, soimpl Iteratoris forward-compatible with changes to its return type. impl Iteratorwon't unify with other opaqueimpl Iteratortypes, even if they happen to have the same underlying type. (In simple terms: the compiler won't allow you to make aVecofimpl Iterators from different sources, even if all those opaque types are the same concrete type.)
Neither of these differences has any influence on code generation or the compiler's ability to inline anything, so go ahead and use impl Iterator.
There is one case where you must still use indirect dispatch (dyn Iterator): when the function neighbours is itself part of a trait, the impl Trait syntax is not yet available (as of 1.59). The best way to solve this at the moment is to return Box. (Note, however, that doesn't mean every call will be dynamically dispatched; the call to .next() will be, but everything "inside" that still uses easily-optimized static dispatch.)
- What is the correct way to return an Iterator (or any other trait)?
- How do I return an instance of a trait from a method?
- https://stackoverflow.com/a/39490692/3650362 (when the method is part of a trait)
¹ Note that in order to actually return Map<...>>>, you would still have to use impl Trait to represent the closures, since they have anonymous types.
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Install traits
You can use traits like any standard Python library. You will need to make sure that you have a development environment consisting of a Python distribution including header files, a compiler, pip, and git installed. Make sure that your pip, setuptools, and wheel are up to date. When using pip it is generally recommended to install packages in a virtual environment to avoid changes to the system.
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