Questions tagged [head]

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4
votes
1answer
47 views

Name of patterns cast as expressions from strings

I'm trying to match a part of a string while imposing conditions on the patterns, e.g.: StringCases["223", a: DigitCharacter ~~ b: DigitCharacter /; Unequal[a, b]] ...
0
votes
1answer
41 views

Count heads: e.g. neglect all terms $\sin(x) \sin (y) \sin (z) \sin (w)$ for all values of the argument

I have a polynomial (functional) expression $E[F]$ in terms of a function $F$. I want to take an $F$-cube truncation in the sense that I want to and make terms of the form $F[w]F[x]F[y]F[z]$ vanish ...
-1
votes
1answer
47 views

Function matching any head (Example: h_[_,_] := 5)

I want to define a function matching any expression with 2 parameters. For example: _[_, _] := 5 I get the following error: SetDelayed::nosym: "[,_] does not ...
0
votes
0answers
21 views

What are all the possible “top level” heads available in Mathematica? [duplicate]

For example, 1, 1.1, f. Their heads are Integer, ...
3
votes
4answers
217 views

How to remove style from a styled number?

For example, I have a number with style like so: Style[1, Red, 20] How do I remove its style, so it returns to its inner value 1...
13
votes
7answers
772 views

Getting the “root” Head

I have a dynamic list of function names, like {f1, f2, f3, ...}, and they will enter in computation in various forms ...
1
vote
1answer
10 views

Parsing the link returned by CloudExport

Consider Is there a way to make a function justLink that parses a CloudObject[<link>] and returns just the string ...
3
votes
2answers
96 views

Extracting terms with certain heads in a function

Given a function with several arguments func[a,b,g1[x],g1[x,y],g2[1],g2[g1[1]],3] I would like to extract all arguments with the head ...
8
votes
1answer
161 views

Why does MatchQ[a, r_ /; Head[r] != Plus] evaluate to False?

I'm trying to understand. Why is it that: MatchQ[a, r_ /; Head[r] != Plus] Evaluates to: False ? For me, I would think ...
22
votes
2answers
2k views

Why no RationalQ or RealQ?

Interesting pattern came up as I go through the homework replies of my students. Why is there no RationalQ or RealQ? We have <...
3
votes
1answer
152 views

Testing Head inside a Module [closed]

I hava a Module in which a want to give a single String or a List as a parameter and I want to change a single String to a List containing this String. So I did the ...
4
votes
1answer
104 views

question about using Heads->True in Cases command

I was trying to find the order of highest derivative of expression. Using solution given in detect-highest-order-of-derivative-in-expression I just do not understand why when removing ...
1
vote
2answers
334 views

Head replacement [duplicate]

Input Code a[1]=UnitVector[4,1] b[1]=1 Now I want replace the head of b[1] by a, ...
4
votes
1answer
76 views

How to obtain a list of all build-in system level Heads?

I am writing a small Mathematical expression parser and need a list of all Mathematica build-in Heads (system context?) so I can check the type of input. Such as ...
8
votes
2answers
190 views

Replace Complex Head with List

I would like to apply ListPlot to a set of complex numbers. This is what comes to mind to convert a complex number to a pair: ...
2
votes
1answer
72 views

Gather element of a list based on their head

I have list of the form {y[-1], y[0], w'[1], y'[0], w'''[-1], z''[-1]} and I would like to gather the elements together based on their heads to have ...
3
votes
1answer
327 views

How can I replace a head on a specific level?

So in my notebook I have a list of long expressions which are sums of a bunch of terms. I would like to look at each of these terms individually and try to remove them based on some criteria. My idea ...
1
vote
1answer
658 views

How to “invert” a rule

The subject is a bit cryptic, I know, but here is what I'd like to do: Let's say I am solving an ODE like this: ...
7
votes
2answers
282 views

How to access Dataset's metadata

A Dataset object has internal metadata. For example, let ds = Dataset[{<|"a" -> 1, "b" -> "x", "c" -> {1}|>}]; ...
2
votes
1answer
71 views

Why is head evaluation inconsistent in pattern replacement?

I noticed the following unexpected result: In[90]:= "foo" /. x_String -> Head[x] Out[90]= Symbol Why is it that Head[x] ...
5
votes
1answer
264 views

How to represent 1 as Symbol[“Integer”]

Maybe this is a boring question, but I cannot figure it out. Because every expression has a Head, and Head[1] is ...
6
votes
1answer
285 views

How to Collect a variable multiplied by a constant?

I'd like to use Collect to get terms that have a variable multiplied by a constant. For example I'd like: Collect[x + b x, b x] ...
4
votes
1answer
567 views

What is the definition of head in Mathematica? [closed]

I know (by practice) what a head is, but I am unable to find the appropriate words to actually define it. I would like to see a precise definition of head using the appropriate technical words ...
1
vote
1answer
198 views

Why does the Derivative function not appear in the tree form? [closed]

I was learning that set delay doesn't evaluate things until its calling time. Hence, I thought that something like the followng: dfdt := D[f[t],t] would not ...
5
votes
2answers
409 views

Is there any way to use head of Real and Integer altogether?

Is there any way to use the head of Integer and Real together like below? The below is not right, I know that, it is just for ...
2
votes
0answers
294 views

Custom Head for Encapsulation

Often when I'm writing a project in Mathematica, the number of arguments I must provide to functions spins out of control. I need a sort of object-oriented encapsulation approach. I've already had a ...
5
votes
1answer
570 views

Pattern matching list of elements with different heads

I have a function, which I want to accept only a list of kind of elements belonging to a group. The task comes down to finding an elegant pattern suitable for easy to read function prototype. As an ...