# Questions tagged [built-in-symbols]

Questions related to handling built-in symbols and functions, for example why they behave a certain (possibly unexpected) way.

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### Div of function evaluates to zero but should be a DiracDelta. How to solve? [closed]

When I attempt to take the divergence of the function $f(r, \theta, \psi) = \hat{r}/r^2$, Mathematica returns zero even though we know mathematically that the answer should be $4\pi \delta(\vec{r})$. ...
261 views

### Largest k such that p^k divides n

(Here all variables are integer.) Is there a built-in function f[n,p] such that f[n,p] = largest k such that p^k divides n For ...
72 views

### Can I tell whether a symbol is build-in (part of the System` library)?

I'd like a function that checks whether a symbol is a predefined part of the language or not. More generally, it might check whether it's part of a given package. ...
84 views

### Built-in functions on the LHS won't pattern-match

I have this pattern-matching problem: F[X_,myminus[X_]]:=0 F[1,myminus] Works. ...
351 views

### AnyTrue is too good (compared to MemberQ)

Let L be a list of integers, and ⓝ denote an explicit integer. I've thought the most natural way to tell whether ⓝ belongs to L is In MemberQ[L, ⓝ] But there ...
42 views

### Definition of large expression - makes PC freezed

In A=Range[10^4];?A Out (* definition of A*) It works for 10^4. But if I increase the number to 10^6 ...
65 views

### Construct really identical function (the same as Length)

In Length[Unevaluated[1 + 1 + 1 + 1]] Out 4 Q1) Can we construct a function named f, such that ...
39 views

### Check an input matrix M contains any nonzero diagonal matrix element or not

Is there a way to easily check an input matrix M contains any nonzero diagonal matrix element or not? For example, if the M contains any nonzero diagonal matrix element, Output: True. if the M ...
98 views

### Get list of special characters

I recently found that \[Gradient] and \[InlinePart] both expand (contract) to special symbols in MMA. So far as I can tell (see ...
72 views

### Is there a function in Mathematica to combine/decompose sinusoids? [closed]

Lets say I have some combination of an arbitrary number of sinusoids with potentially varying magnitudes, phase angles and frequencies that I would like to compose into a singular sinusoid, is there a ...
45 views

### How to reconstruct a complicated built-in function (e.g. for modification or use in a version that does not have it yet) [duplicate]

Is it possible to extract the definitions for a built-in function to reconstruct a similar user defined function. This would be useful to port new mathematica functionality to older versions or to ...
452 views

### very simple but unexpected aspect of Function[ ]

I've always thought (2#+1)& and Function[x,2x+1] are interchangeable in common sense. But, ...
48 views

### Find fit for 3D data

Consider some dataset in the form {x,y,data[x,y]}: ...
45 views

### What could go wrong in redefining Power to act on functions?

Inspired by a tweet (from a locked account, unfortunately, so I can't link it), we can get notation like $\cos^2(x)$ to work in Mathematica in general: ...
54 views

### How to define distributivity of CenterDot on bras and kets

I am working on a code for a coupled quantum harmonic oscillator and found myself in a hiccup when trying to evaluate the inner product of linear combinations of bras and kets. I have initially ...
71 views

### How to arrange two tables in the following way?

Consider two tables: ...
266 views

Can we say Head[x] and x[] are identical ? In mathematica manual I could find : 'The head is the part with index 0' But I am not sure whether Head[x] are x[] are really interchangeable in any ...
63 views

### A condition for the given point to be included in the domain?

If we have two domains, it is possible to check whether one domain is inside another domain: ...
95 views

### A condition for one domain to be included in another domain?

Consider two domains: domain1 = Rectangle[{-2.5, -2.5}, {2.5, 2.5}]; domain2[R_] := Disk[{0, 0}, R] I would like to check whether the second domain is completely ...
82 views

### How to find the area of circle inside the rectangle?

Consider a circle located at the origin circ[R_] := Circle[{0,0},R] and an arbitrary rectangle ...
48 views

### Dot Product doesn't behave like normal function

I am trying to slightly modify the Dot function by treating it like a usual function, but soon I notice something weird about it. Suppose there is a set ...
64 views

### Counting the number of edges between two graph partitions

Consider the following: g = RandomGraph[WattsStrogatzGraphDistribution[1000, 0.1, 5]] comm = FindGraphPartition[g, 2]; CommunityGraphPlot[g, comm] ...
119 views

### How &@ and &/@works?

I have the following expression: (Join[#, Reverse[#, {2}]] &@Partition[#, 2, 1, 1]) & /@ Vec (* where: *) Vec={{2,0},{1,1},{0,2}}, but I am not sure how ...
360 views

### Compare all elements of a set with a specific number and return 1 or 0

Say I generate a set of 20 random numbers by x=RandomReal[{0, 1}, 20], I want to compare every element of x with 0.4. If it is less than or equal to 0.4, then return 1; if it is greater than 0.4, then ...
52 views

### Avoiding Tables, Do and other loop construction

In my work I have a lot of cases, where I should calculate non-listable functions for a quite large number of points. To be more concrete, consider first listable function ...
77 views

### How to figure out syntax for symbols?

I'm new to Mathematica and am having a hard time figuring out how to type certain symbols when I read the documentation. For example, in https://reference.wolfram.com/language/ref/...
968 views

### Which function names have been re-purposed in Mathematica after being deprecated?

I have just learned about the new function Splice from this answer. It turns out that this function used to have a completely different usage! (See below.) To me, ...
463 views

### Finding year that MMA functions were introduced via programmatic calls in the Wolfram Language [duplicate]

Is there a way to find the year that MMA functions were introduced via programmatic calls in the Wolfram Language? I would like to be able to create and manipulate such a list or dataset.
41 views

### What built-in functions have bad time/space complexity and their alternatives?

It's surprising that Join is $\mathcal{O}(n)$ (due to copy) while I've been using it as a convenient way to join lists together. It also reminds me of suggestions ...
104 views

### How can I prevent TabView from resetting the current tab?

This is a simplification of a problem that has arisen in a project regarding Euclidean activities for verifying proportions via operations on pairs of magnitudes. In the project, the LocatorPane is ...
107 views

### Customized priority function in DataStructure["PriorityQueue"]?

I'm using Mathematica 12.1. The documentation for DataStructure["PriorityQueue"] claims that, ... the highest-priority element is always returned. The ...
71 views

### Define trace-like function (e.g. cyclically invariant) involving operators without built-in meaning

I am interested in defining a function, say $\mathrm{Tra}$, that imply operators without build-in meaning, say it involves products with the $\cdot$ (Esc . Esc), ...
59 views

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### Pattern matching and NonCommutativeMultiply

I am trying to define some functions using NonCommutativeMultiply and I am experiencing some strange behavior. Consider the following expression ...
69 views

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### Error Message for GrammarRules and GrammarApply

I have been struggling with the following issue regarding an irregularity when deploying and applying GrammarRules. Specifically, it often takes several failed attempts before the execution is ...