aliasing

问题 For optimisation reasons, Fortran enforces that the dummy arguments of a subroutine or function are not alias, i.e., they do not point the the same memory place. I am wondering if the same constraint applies to the returned value of a function. In other words, for a given myfunc function: function myfunc(a) real, intent(in) :: a(:) real :: myfunc(size(a)) myfunc = a * 2 end function myfunc is it standard-compliant to write: a = myfunc(a) and b = myfunc(a) ? 回答1: The arguments of a function

问题 I need to draw a path along the shape of an image in a way that it is always matching its position on the image independent of the image scale. Think of this like the hybrid view of Google Maps where streets names and roads are superimposed on top of the aerial pictures. Furthermore, this path will be drawn by the user's finger movements and I need to be able to retrieve the path keypoints on the image pixel coordinates. The user zooms-in in order to more precisely set the paths location. I

问题 It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center. Closed 6 years ago . namespace A { #include <iostream> }; int main(){ A::std::cout << "\nSample"; return 0; } 回答1: Short answer: No. Long answer: Well, not really. You can fake it, though. You can declare it outside and use using

问题 I understand that having a const method in C++ means that an object is read-only through that method, but that it may still change otherwise. However, this code apparently changes an object through a const reference (i.e. through a const method). Is this code legal in C++? If so: Is it breaking the const -ness of the type system? Why/why not? If not: Why not? Note 1: I have edited the example a bit, so answers might be referring to older examples. Edit 2: Apparently you don't even need C++11,

问题 I have created a stripped down JSFiddle of my D3 chart. I have made it responsive (with viewbox and preserveaspectratio) using the solution at: responsive D3 chart When I resize the window and make it smaller, some of the grid lines seem to be disappearing and reappearing. I presume this will look bad at small resolutions (eg. 320x480 mobile phone). Is there a way to preserve my gridlines when the window gets resized smaller? HTML code: <!--//d3 chart//--> <div class="centre-div"></div> CSS

问题 Quote from C99 standard: 6.5.2.3 5 One special guarantee is made in order to simplify the use of unions: if a union contains several structures that share a common initial sequence (see below), and if the union object currently contains one of these structures, it is permitted to inspect the common initial part of any of them anywhere that a declaration of the complete type of the union is visible. Two structures share a common initial sequence if corresponding members have compatible types

问题 I've a wall and a brick texture in my OpenGL 2 scene that keeps shimmering and flashing no matter what I set. When I'm zoomed in close (and can see clearly the texture), then the flashing and shimmering stops. But when I'm zoomed out and moving around the scene, the flashing and shimmering is very pronounced. This is the texture code for the brick wall: brickwall.setTexParameteri(gl, GL2.GL_TEXTURE_WRAP_S, GL2.GL_REPEAT); brickwall.setTexParameteri(gl, GL2.GL_TEXTURE_WRAP_T, GL2.GL_REPEAT);

问题 I have a SQL SELECT in which I aliased MIN(A.product_id + 1) to 'min': $product='SELECT * FROM '.$table.' WHERE product_id > '.(($div_id)*10000).' AND product_id < '.((($div_id+1)*10000)-1).''; $select='SELECT MIN(A.product_id + 1) AS min FROM ('.$product.') A LEFT JOIN ('.$product.') B ON A.product_id = B.product_id - 1 WHERE B.product_id Is NULL'; this is the result in phpMyAdmin: But in php I have 'min' => NULL $result = mysql_query($select, $con); $row=mysql_fetch_assoc($result); echo

问题 In an old program I serialized a data structure to bytes, by allocating an array of unsigned char, and then converted ints by: *((*int)p) = value; (where p is the unsigned char* , and value is the value to be stored). This worked fine, except when compiled on Sparc where it triggered exceptions due to accessing memory with improper alignment. Which made perfect sense because the data elements had varying sizes so p quickly became unaligned, and triggered the error when used to store an int

问题 I'm trying to deal with aliases (friendly-urls) and probably I'm not doing it right. What I want to do is to transform urls like '/blog/my-post-about-something' into '/posts/23'. I have written a listener for the kernel.request event that makes some operations and modifies the original request class RequestListener { public function onKernelRequest(KernelEvent $event) { $request = $event->getRequest(); $converted_path = $this->getPathIfAny($request); if ($converted_path) { $request->server-