## functions – Unexpected behaviour with Coefficient

If I run

``````expr = (CF G(0, zb))/(1 - zb) + (CF zb^2 G(0, zb))/(1 - zb) + (2 CF G(1, zb))/(1 - zb) + (2 CF zb^2 G(1, zb))/(1 - zb);
Coefficient(expr, zb, -1)
``````

in Mathematica 12.1, it returns

``````-((CF G(0, zb))/(-1 + zb)) - (2 CF G(1, zb))/(-1 + zb)
``````

Shouldn’t it return 0 since there are no terms in the form 1/zb in expr ?

## How should a bytecode VM call external C functions?

I am trying to implement a basic bytecode VM, which I plan to target with a compiler. How can I implement the ability to call external C functions using the bytecode, i.e., call arbitrary functions in runtime. For example, my future compiler should be able to produce programs that call `printf()`, `malloc()`, etc. My guess is you could somehow ask the OS for the needed functions address and jump to it, probably making use of things like `dlopen()` and `dlsym()`, however I don’t know the exact details and the specifics on implementing that in a VM.

## dg.differential geometry – A characterization of functions which Riemannian Hessian equal to zero

Consider Euclidean space $$mathbb{R}^n$$, and measure distances in this space with some Riemannian metric $$M(x)$$. That is, for two points $$x, y$$, define $$d(x, y)$$ to be equal to
$$d(x, y) = inf_{gamma(cdot) in Gamma_{x, y}}sqrt{int_0^1 dot{gamma}(s)^{mathsf{T}}M(gamma(s))dot{gamma}(s)ds},$$ where $$Gamma_{x, y}$$ denotes the set of all curves over $$(0, 1)$$ satisfying $$gamma(0) = x, gamma(1) = y$$.

I’m interested in characterizing the set of “linear” functions with respect to this metric. That is, what are all functions that have Riemannian Hessian equal to zero in this metric? I understand that, on a compact Riemannian manifold, such functions are trivial. But what about a manifold with a single global chart as I’ve constructed here?

## c# – How to just pass in primary key values to my CRUD functions?

Here is my code:

albums.cshtml

``````@page
@model Project.Pages.AlbumsModel

<div class="row">
<h1 class="display-2">Albums</h1>
<table class="table">
<tr>
<th>Album ID, artist ID, Album title</th>
</tr>
<tbody>
@foreach (string album in Model.Albums)
{
<tr>
<td>@album</td>
<td><a asp-page="/Albums/Delete" asp-route-id="@album">Delete</a></td>
<td><a asp-page="/Albums/Edit" asp-route-id="@album">Edit title</a></td>
</tr>
}
</tbody>
</table>
</div>
<div class="row">
<p>Enter a title & ArtistID for a new album:&nbsp;</p>
<form method="POST">
<div><input asp-for="Album.Title" /></div>
<div><input asp-for="Album.ArtistId" /></div>
<input type="submit" />
</form>
</div>
``````

albums.cshtml.cs

``````using Microsoft.AspNetCore.Mvc.RazorPages;
using System.Collections.Generic;
using System.Linq;
using Microsoft.AspNetCore.Mvc;
using Project.Models;
using System;

namespace Project.Pages
{
public class AlbumsModel : PageModel
{
private Chinook db;

public AlbumsModel(Chinook injectedContext)
{
db = injectedContext;
}
public IEnumerable<string> Albums { get; set; }
public void OnGet()
{
ViewData("Title") = "Chinook Web Site - Albums";
Albums = db.Albums.Select(s => s.AlbumId.ToString() + ". " + s.ArtistId + ". " + s.Title);
}
(BindProperty)
public Album Album { get; set; }

public IActionResult OnPost()
{
if (ModelState.IsValid)
{
db.SaveChanges();
return RedirectToPage("/albums");
}
return Page();
}

public IActionResult DeleteAlbum(int AlbumId)
{
var album = db.Albums.Find(AlbumId);

if (album == null) return Page();

db.Albums.Remove(album); db.SaveChanges(); return RedirectToPage("/albums");
}
}
}
``````

delete.cshtml

``````@page  "{id?}"
@model Project.Pages.Albums.DeleteModel

@{
ViewData("Title") = "Delete";
}

<h1>Delete</h1>

<p class="text-danger">@Model.ErrorMessage</p>

<h3>Are you sure you want to delete this?</h3>
<div>
<h4>Album</h4>
<hr />
<dl class="row">
<dt class="col-sm-2">
@Html.DisplayNameFor(model => model.Album.Title)
</dt>
<dd class="col-sm-10">
@Html.DisplayFor(model => model.Album.Title)
</dd>
<dt class="col-sm-2">
@Html.DisplayNameFor(model => model.Album.ArtistId)
</dt>
<dd class="col-sm-10">
@Html.DisplayFor(model => model.Album.ArtistId)
</dd>
<dt class="col-sm-2">
@Html.DisplayNameFor(model => model.Album.AlbumId)
</dt>
<dd class="col-sm-10">
@Html.DisplayFor(model => model.Album.AlbumId)
</dd>
</dl>

<form method="post">
<input type="submit" value="Delete" asp-route-id="@Model.Album.AlbumId" class="btn btn-danger" /> |
<a asp-page="/Albums">Back to List</a>
</form>
</div>
``````

delete.cshtml.cs

``````#region snippet_All
using Project.Models;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;
using Microsoft.EntityFrameworkCore;

namespace Project.Pages.Albums
{
public class DeleteModel : PageModel
{

public DeleteModel(Chinook context)
{
_context = context;
}

(BindProperty)
public Album Album { get; set; }
public string ErrorMessage { get; set; }

public async Task<IActionResult> OnGetAsync(string? id, bool? saveChangesError = false) //changed int -> string
{
if (id == null)
{
return NotFound();
}
//using string.split method to split the id parameter, and get the albumid.
var albumid = System.Convert.ToInt32(id.ToString().Split('.')(0));

Album = await _context.Albums
.AsNoTracking()
.FirstOrDefaultAsync(m => m.AlbumId == albumid);

if (Album == null)
{
return NotFound();
}

if (saveChangesError.GetValueOrDefault())
{
ErrorMessage = "Delete failed. Try again";
}

return Page();
}

{
if (id == null)
{
return NotFound();
}

var album = await _context.Albums.FindAsync(id);

if (album == null)
{
return NotFound();
}

try
{
_context.Albums.Remove(album);
await _context.SaveChangesAsync();
return RedirectToPage("/Albums");
}
catch (DbUpdateException /* ex */)
{
//Log the error (uncomment ex variable name and write a log.)
return RedirectToAction("/Albums/Delete",
new { id, saveChangesError = true });
}
}
}
}
#endregion
``````

edit.cshtml

``````@page
@model Project.Pages.Albums.EditModel

@{
ViewData("Title") = "Edit";
}

<h1>Edit</h1>

<h4>Album</h4>
<hr />
<div class="row">
<div class="col-md-4">
<form method="post">
<div asp-validation-summary="ModelOnly" class="text-danger"></div>
<input type="hidden" asp-for="Album.AlbumId" />
<div class="form-group">
<label asp-for="Album.Title" class="control-label"></label>
<input asp-for="Album.Title" class="form-control" />
<span asp-validation-for="Album.Title" class="text-danger"></span>
</div>
<div class="form-group">
<input type="submit" value="Save" class="btn btn-primary" />
</div>
</form>
</div>
</div>

<div>
<a asp-page="/Albums">Back to List</a>
</div>

@section Scripts {
@{await Html.RenderPartialAsync("_ValidationScriptsPartial");}
}
``````

edit.cshtml.cs

``````using Project.Models;
using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.RazorPages;
using Microsoft.AspNetCore.Mvc.Rendering;
using Microsoft.EntityFrameworkCore;

namespace Project.Pages.Albums
{
public class EditModel : PageModel
{

public EditModel(Chinook context)
{
_context = context;
}

(BindProperty)
public Album Album { get; set; }
public string ErrorMessage { get; set; }

#region snippet_OnGetPost
// public async Task<IActionResult> OnGetAsync(int? id)
// {
//     if (id == null)
//     {
//         return NotFound();
//     }

//     Album = await _context.Albums.FindAsync(id);

//     if (Album == null)
//     {
//         return NotFound();
//     }
//     return Page();
// }

public async Task<IActionResult> OnGetAsync(string? id, bool? saveChangesError = false) //changed int -> string
{
if (id == null)
{
return NotFound();
}
//using string.split method to split the id parameter, and get the albumid.
var albumid = System.Convert.ToInt32(id.ToString().Split('.')(0));

Album = await _context.Albums
.AsNoTracking()
.FirstOrDefaultAsync(m => m.AlbumId == albumid);

if (Album == null)
{
return NotFound();
}

if (saveChangesError.GetValueOrDefault())
{
ErrorMessage = "Delete failed. Try again";
}

return Page();
}

{
var albumToUpdate = await _context.Albums.FindAsync(id);

if (albumToUpdate == null)
{
return NotFound();
}

if (await TryUpdateModelAsync<Album>(
albumToUpdate,
"album",
s => s.Title))
{
await _context.SaveChangesAsync();
return RedirectToPage("/Albums");
}

return Page();
}
#endregion

private bool AlbumExists(int id)
{
return _context.Albums.Any(e => e.AlbumId == id);
}
}
}
``````

My code build and runs OK, but when I go to edit, I get, for instance

This localhost page canâ€™t be found
No web page was found for the web address: https://localhost:5001/Albums/Edit/353.%20123.%20Test

I’m sure it should just be passing in the `AlbumId`, as in

https://localhost:5001/Albums/Edit/353

…and when I manually change the URL to that, it works.

The delete function works from, for instance…

https://localhost:5001/Albums/Delete/353.%20123.%20Test2

…where ‘353’ is the `AlbumId`, ‘123’ is the `ArtistId`, and ‘Test2’ is the `Title`.

…but that actually does work. So how can I just get both Delete and Edit to work from the `AlbumId`? That is all that’s needed, right? TIA for any help.

## time complexity – Existence of a function between two functions \$f\$ and \$g\$ where \$f in o(g)\$

Yes.

For example, let $$h=sqrt{fg}$$, assuming $$f$$ and $$g$$ are positive.

If not, we can let $$h(x)=max(sqrt{|f(x)g(x)|}, g(x)/(|x|+1))$$. The term, $$g(x)/(|x|+1)$$ makes sure that $$h(x)$$ will stay positive eventually.

Exercise. For each two functions $$f$$ and $$g$$, where $$f in omega(g)$$, there exists a function $$h$$ where $$f in omega(h)$$ and $$h in omega(g)$$.

## Continuos functions nowhere differentiable

If: $$D(x) = sum^infty_{k=1}frac{1}{k!}sin((k+1)!x)$$ How can I prove that $$D(x)$$ is nowhere differentiable on $$mathbb{R}$$

## parametric functions – How to initiate a matrix with indexed parameters

I couldn’t find it in the documentation, so I’m posting it here.
I want to create two by two matrices as follows:
$$`W = begin{bmatrix}w_{11} & w_{12} \ w_{21} & w_{22} end{bmatrix}, V = begin{bmatrix}v_{11} & v_{21} \ v_{12} & v_{22} end{bmatrix}`$$
so I could calculate $$V^{-1}$$ and see the result with the parameters $$v_{ij}$$‘s.

Tnx.

## functions – WordPress wp_dequeue_script remove all other scripts

I want to override function in child theme to remove specific scripts, which is defined inside a class in parent theme.

Parent theme `functions.php`

``````class Theme_Assets extends Theme_Base {

/**
* Hold data for wa_theme for frontend
* @var array
*/
private static \$theme_json = array();

/**
* (__construct description)
* @method __construct
*/
public function __construct() {

// Frontend

));
}

/**
* Unregister Scripts and Styles
* @method dequeue
* @return (type)  (description)
*/
public function dequeue() {

}

/**
* Register Scripts and Styles
* @method register
* @return (type)   (description)
*/
public function register() {

\$this->script( 'bootstrap', \$this->get_vendor_uri( 'bootstrap/js/bootstrap.min.js' ), array( 'jquery' ) );
\$this->script( 'intersection-observer', \$this->get_vendor_uri( 'intersection-observer.js' ), array( 'jquery' ) );
\$this->script( 'jquery-vivus', \$this->get_vendor_uri( 'vivus.min.js' ), array( 'jquery' ) );
\$this->script( 'splittext', \$this->get_vendor_uri( 'greensock/utils/SplitText.min.js' ), array( 'jquery' ) );
\$this->script( 'scrollmagic', \$this->get_vendor_uri( 'scrollmagic/ScrollMagic.min.js' ), array( 'jquery' ) );
\$this->script( 'jquery-tinycolor', \$this->get_vendor_uri( 'tinycolor-min.js' ), array( 'jquery' ) );

\$deps = array(
'bootstrap',
'intersection-observer',
'scrollmagic',
);

if( 'on' === \$enable_lazyload ) {
array_push( \$deps,
);
}
if( 'on' === \$enable_header ) {
array_push( \$deps,
'jquery-tinycolor'
);
}

if( is_page() ) {
array_push( \$deps,
'splittext',
'jquery-tinycolor'
);
}
}

/**
* Enqueue Scripts and Styles
* @method enqueue
* @return (type)  (description)
*/
public function enqueue() {

}
}

// Register Helpers ----------------------------------------------------------
public function script( \$handle, \$src, \$deps = null, \$in_footer = true, \$ver = null ) {
wp_register_script( \$handle, \$src, \$deps, \$ver, \$in_footer);
}

public function style( \$handle, \$src, \$deps = null, \$ver = null, \$media = 'all' ) {
wp_register_style( \$handle, \$src, \$deps, \$ver, \$media );
}

// Uri Helpers ---------------------------------------------------------------

public function get_theme_uri(\$file = '') {
return get_template_directory_uri() . '/' . \$file;
}

public function get_child_uri(\$file = '') {
return get_stylesheet_directory_uri() . '/' . \$file;
}

public function get_css_uri(\$file = '') {
return \$this->get_theme_uri('assets/css/'.\$file.'.css');
}

public function get_elements_uri( \$file = '' ) {
return \$this->get_theme_uri( 'assets/css/elements/' . \$file . '.css' );
}

public function get_js_uri(\$file = '') {
return \$this->get_theme_uri('assets/js/'.\$file.'.js');
}

public function get_vendor_uri(\$file = '') {
return \$this->get_theme_uri('assets/vendors/'.\$file);
}
}

new Theme_Assets;
``````

I want to remove ‘splittext‘ and ‘jquery-tinycolor‘ scripts by inheriting `dequeue` function in parent theme but it remove all other scripts

Here is Child theme’s code in `functions.php`

``````add_action( 'after_setup_theme', function() {

class D extends Theme_Assets{

function __construct(){
}

public function dequeue(){
wp_dequeue_script('jquery-tinycolor');
wp_deregister_script('jquery-tinycolor');
wp_dequeue_script('splittext');
wp_deregister_script('splittext');
}
}

new D();
});
``````

Any helps are appreciate.

## programming languages – Dfferences in c++ about how variables are used in functions and when to use int

I would want to know why code::blocks do not print the same thing if I write the next sequence of code:

``````int n,m,a(11)(11),x(11),y,z,v(11),i;
int va(int k)
{
return a(x(k-1))(i) && !v(i);
}
int s(int k)
{
return i==y;
}
void t(int k)
{
for(int j=1; j<=k; j++)
cout<<x(j)<<' ';
cout<<endl;
}
void ck(int k)
{
for(int i=1; i<=n; i++)
if(va(k))
{
v(i)=1;
x(k)=i;
if(s(k))
{
t(k);
}
else ck(k-1);
v(i)=0;
}
}
``````

as when I write the following one:

``````int n,m,a(11)(11),x(11),y,z,v(11),i;
int va(int k)
{
return a(x(k-1))(i) && !v(i);
}
int s(int k)
{
return x(k)==y;
}
void t(int k)
{
for(int j=1; j<=k; j++)
cout<<x(j)<<' ';
cout<<endl;
}
void ck(int k)
{
for(int i=1; i<=n; i++)
if(a(x(k-1))(i) && !v(i))
{
v(i)=1;
x(k)=i;
if(s(k))
{
t(k);
}
else ck(k+1);
v(i)=0;
}
}
``````

or the following one:

``````int n,m,a(11)(11),x(11),y,z,v(11),i;
int valid(int k)
{
return a(x(k-1))(i) && !v(i);
}
int solutie(int k)
{
return i==y;
}
void tipar(int k)
{
for(int j=1; j<=k; j++)
cout<<x(j)<<' ';
cout<<endl;
}
void ck(int k)
{
for(i=1; i<=n; i++)
if(a(x(k-1))(i) && !v(i))
{
v(i)=1;
x(k)=i;
if(s(k))
{
t(k);
}
else ck(k+1);
v(i)=0;
}
}
``````

## Composite and one-one functions.

I wanted to know if gof is defined and is one-one then under what conditions will both g and f be one-one? Particularly is it possible if f:A->B and g:B->A ?