Given `id`

is the identity function `\x.x`

, we surely know `id x = x`

by beta reduction. Do we also have `x id = x`

?

# Tag: function

## Getting error>: ‘invalid use of non-static member function’ when passing a child class method to a father (public-inherited) method

Hope everybody is doing just fine.

I’m writing this piece of code where i have a class called XZStage (child) that inherits every public method from the library/class SerialCommand (father) and on a method of the XZStage i’m passing to a father method, a child method as argument.

The error i’m getting is: ‘invalid use of non-static member function’

A little piece of advice to do a refined search would be great.

## Average value of function with 2 variables

How would I determine the average value of a function of two intervals, both of which have given bounds if the function f[x,y] (below) has bounds x,y=[0,5]. I assume by using the integration function, but I’ve only done that with a function of 1 variable.

`Sqrt[1 + .25y^2 ((2.5 + 1.5 Cos[Pi/3 x] - 2.75)^2 + y^2(2.4 + 1.1 Sin[Pi/3 x] - 3.75)^2)] `

## How does the Hellfire Warlock’s hellfire blast function?

I’m trying to properly understand the Hellfire Warlock’s *hellfire blast*.

Hellfire Blast (Sp):Whenever you use your eldritch blast ability, you can change your eldritch blast into a hellfire blast. A hellfire blast deals your normal eldritch blast damage plus an extra 2d6 points of damage per class level. If your blast hits multiple targets (for example, the eldritch chain or eldritch cone blast shape invocations), each target takes the extra damage. This damage is not fire damage. Hellfire burns hotter than any normal fire, as described in the sidebar on page 119.Each time you use this ability, you take 1 point of Constitution damage. Because the diabolical forces behind the power of hellfire demand part of your essence in exchange for this granted power, if you do not have a Constitution score or are somehow immune to Constitution damage, you cannot use this ability.

**1. Is all the damage from a hellfire blast considered hellfire or only the extra damage?**

Eldritch Essence InvocationsSome of a warlock’s invocations, such as frightful blast, modify the damage or other effects of the warlock’s eldritch blast. These are called eldritch essence invocations. Unless noted otherwise, eldritch blasts modified by eldritch essence invocations deal damage normally in addition to imparting the effects described in the invocation description.

A warlock can apply only one eldritch essence invocation to a single eldritch blast, choosing from any of the eldritch essence invocations that he knows. When a warlock applies an eldritch essence invocation to his eldritch blast, the spell level equivalent of the modified blast is equal to the spell-level of the eldritch blast or of the eldritch essence invocation, whichever is higher. If a warlock targets a creature with an eldritch essence blast that has immunity to the invocation’s effect, it still takes the damage from the blast normally (provided it isn’t also immune to the eldritch blast).

A warlock can apply an eldritch essence invocation and a blast shape invocation (see below) to the same blast. When a warlock uses both kinds of invocations to alter an eldritch blast, the spell level equivalent is equal to the spell level of the eldritch blast, the level of the eldritch essence invocation, or the level of the blast shape invocation, whichever is higher. (Complete Arcane, pp. 8-9)

–

Vitriolic BlastThis eldritch essence invocation allows you to change your eldritch blast into a vitriolic blast. A vitriolic blast deals acid damage, and it is formed from conjured acid, making it different from other eldritch essences because it ignores spell resistance. Creatures struck by a vitriolic blast automatically take an extra 2d6 points of acid damage on following rounds. This acid damage persists for 1 round per five class levels you have. For example, a 15th-level warlock deals 2d6 points of acid damage per round for 3 rounds after the initial vitriolic blast attack. (Complete Arcane, p. 136)

**2. Can a hellfire blast also be a vitriolic blast? If it can, is it hellfire or acid? If it’s hellfire does it still ignore spell resistance and do an extra 2d6 points of damage on following rounds”?**

## Function of Maximum and Minimum Functions of Two Functions

I try to answer this question The Maximum and Minimum Functions of Two Functions

I wrote the following code

`f[x_, y_] := 1 + 2*x + 3*y^3 g[x_, y_] := y + x^2 maxi[x_, y_] := Refine[{(f[x, y] + g[x, y])/2 + Abs[f[x, y] - g[x, y]]/2}, Assumptions -> {0 <= x <= 1, 0 <= y <= 1}] Plot3D[maxi[x, y], {x, 0, 1}, {y, 0, 1}] `

Is there any way to find function of `maxi`

?

## Do supernatural abilities that “function like spells” satisfy prestige class requirements?

For example, say you have 2 levels in Dweomerkeeper, meaning you have Arcane Sight (Su). Does this count as one of the two required divination spells to take levels in Unseen Seer?

## 2D function on a 3D plot

I’m trying to put an ellipse given by:

{2.5 + 1.5 Cos[Pi/3 t], 2.4 + 1.1 Sin[Pi/3 t]}, {t, 0, 6}

onto a 3D plot of a large function composed of several different parts, which essentially displays a mountain range. How do I get the 2D ellipse to show up on the 3D plot? For reference, my 3D plot is given by:

Plot3D[m[x, y], {x, 0, 5}, {y, 0, 5}

I won’t put m[x,y] here because it will take up very much space, but it is essentially 4-5 peaks over the given interval.

## How to create custom search form function including post “tags”

This is my HTML:

`<input type="text" class="keyword" name="keyword" id="keyword" placeholder="Search video..."> <button id="search-keyword">Search</button> `

When I click the “Search” button start a script like this:

`if($ ('.current').hasClass('search-select')){ action = 'my_create_posts_search'; //php function to do ab = document.getElementsByClassName('keyword')[0].value; //get the value of input } `

Then an Ajax function starts:

` $ .ajax({ type: "POST", url: ajax_params.ajax_url, //wordpress ajax data: { 'action': action, //php function to do 'ab': ab, //value of input }, `

Then the action start and the code excecuted is this:

`function my_create_posts_search($ name) { //Pagination for posts $ response = ''; $ paged = (int) (!is_null($ _POST['clicked_times'])) ? $ _POST['clicked_times'] : 0; $ postsPerPage = 18; $ postOffset = $ paged * $ postsPerPage; $ args = array( 'posts_per_page' => $ postsPerPage, //pagination 'offset' => $ postOffset, //pagination 'category' => 42, //post category 's' => $ name, //value of input 'orderby' => 'date', 'order' => 'DESC', ); ... other things... } `

Everything works perfectly expcet when I would like to search by Post Tags.

How can I implement this feature?

I hope my code will help you. Thanks!

## How do I program a function to generate a secure Block Cipher Encryption-Key?

I am currently studying the most widely known encryption algorithms and methodologies. For practice purposes, I am currently pursuing a project where I just implement everything from ECB to RSA as some kind of a C crypto library.

I wanted to ask, how I would generate a more or less secure key in a C program (i know, that writing a crypto library on my own is not secure at all but I just want to learn basic principles from key generating to key exchanging to encryption mechanisms).

So, how could I approach the problem of implementing an algorithm for a secure key generation? Which main issues need to be considered to reach an at least mediocre key security?

## The replacement function is an integral and the double integral yields a different answer than the normal double integral

I am fairly new to Mathematica. I have a quick inquiry. The code is simple and just 3 lines. Trying to do a replacement rule as follows

`ruletrr = intsl[exp_] :> Integrate[exp, {u, u, 1}] intsl[Integrate[a[u],{u,0,u}]]/.ruletrr `

So basically I want replace the expression inside the square brackets after ‘intsl’ with integrating the expression from u to 1. The expression inside the square bracket is in fact an integral as well. The integrand is a function of u. However, after the second line, the answer is as follows

`(1 - u)*Integrate[a[u], {u, 0, u}] `

The answer means that Mathematica takes the expression inside the square bracker as a constant and not a function of u. Kindly copy the preceding line to see the integration symbol as I can’t do it here.

The problem is the first two line is equivalent to the following code line

`Integrate[a[u], {u, u, 1}, {u, 0, u}] `

The answers are different. Can someone let me know where is the mistake here or why is the integral evaluated.

The entire code input is as follows as a summary

`ruletrr = intsl[exp_] :> Integrate[exp,{u,u,1}] intsl[Integrate[a[u],{u,0,u}]]/.ruletrr Integrate[a[u], {u, u, 1}, {u, 0, u}] `

The first two lines are equivalent to the third line but the answers are different

Thanks in advance,

Ehab Emad