Questions about how Mathematica evaluates expressions, tracing evaluation (Trace*), handling expressions in unevaluated form (Hold*, Unevaluated), nonstandard evaluation, etc.

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5
votes
4answers
539 views

Delayed evaluation of assignment

I have a set of PDE's that depend on parameters. They depend on many parameters, but for simplicity we can here assume that they depend only on one, say a. I want ...
0
votes
1answer
45 views

Why returning False? [closed]

Can anyone explain the false? I'm trying to grab co-efficient in front of X^2 I think. I say I think as I'm following my tutors example using his screenshot the only difference between his question ...
2
votes
0answers
184 views

Mathematica shift-enter problem

Would really appreciate if someone can help with this problem: When I first open a Mathematica note book, say you do 1+2 and press shift-enter. As expected, I get "3" as the output. Now suppose you ...
3
votes
0answers
79 views

Functional-Style Fixed-Length Queue Object?

Following up on question Side-effecting an array in an association? and @Mr.Wizard's answer in there, I'm modernizing and tweaking Daniel Lichtblau's efficient queues and ran into a little roadblock. ...
1
vote
2answers
105 views

Is this caused by round-off errors?

Let's consider this integration Integrate[ E^(4 n x s) (1 - x)^(-1 + 4 n μ) x^(-1 + 4 n ν), {x, 0, 1}] It returns ...
0
votes
2answers
61 views

Failed to use N[%] for a infinite series

I am trying to evaluate a infinite series: $$ 2 \sum _{l=1}^{\infty } \Re\left(n^{\frac{2 i \pi l}{\log (q)}} \Gamma \left(\alpha -\frac{2 i l \pi }{\log (q)}\right)\right) $$ With the code: ...
5
votes
2answers
238 views

Associativity of `/@` [duplicate]

Why are the following not equivalent: Map[Line, Map[(Print[#]; #) &, {{{2, 1}, {1, 1}}, {{-2, 1}, {3, 1}}}]] which produces ...
4
votes
3answers
146 views

Getting terms and only evaluate specific parts

I want to expand the expression but I do not want it to evaluate. Sum[(HoldForm[1/(2 # - 1) - 1/(2 # + 1)] &)[i], {i, 1, 6}] However if you evaluate this you ...
3
votes
2answers
346 views

How to NOT simplify fraction

How can I prevent Mathematica from simplifying fractions? What I would like to do is run a test on a list of fractions to see how many are in their reduced form. For example, I have a list: ...
0
votes
1answer
52 views

Unknown Power showing up in Formula [closed]

I have the following worksheet below. (I took a screen shot because I didn't know how to type the code for the particular function). Circled in red are powers that shouldn't be there and yet ...
21
votes
2answers
501 views

Context unique to each group at a specified level

Are there any new tools in v10 that might be applicable to this problem? Recent versions of Mathematica provide the option of having a unique $Context for each ...
0
votes
0answers
107 views

How to speed up my code with constructing matrices

I have run this program for a long time to get the result for n = 2048(about 5hours) and no more result till now (can't run with n = 4096). I would know how to make it more efficient. Any help or ...
5
votes
1answer
175 views

How to understand the difference between Sqrt and Log after ClearAll them

I came across this post, here I change the last line of the code Unprotect[Sqrt]; Sqrt[x_] = "blahblah"; Protect[Sqrt]; Sqrt[2] "blahblah" ...
10
votes
2answers
350 views

When must I use the Return function?

In a comment to my answer to this question, QuantumDot asks, "Where can I find more information on when I must use the 'Return' function?". I found this too deep a question to be answered by leaving a ...
0
votes
0answers
77 views
5
votes
2answers
121 views

Why does Rule behave like this?

Why does {x, x^2, x^3, a, b} /. x^n_ -> f[n] result in {x, f[2], f[3], a, b} when ...
3
votes
3answers
129 views

UpValues evaluation with Dot operator

I would like to simplify some database notation, and I'm doing some tests with UpValues for that. For example, if I set this Upvalue fot tab1: ...
1
vote
0answers
108 views
1
vote
1answer
52 views

Package function not evaluating

I have a short package like this: ...
1
vote
1answer
64 views

Aborting from a Dialog box

I'm trying to abort a While cycle, with a dialog box. I've tried the following: ...
13
votes
1answer
451 views

Evaluation indicator for a notebook

I have a GUI with a number of TabView and other Manipulate controls. Sometimes clicking from one tab view to the other can take ...
6
votes
2answers
189 views

Difference between Evaluation>>Quit Kernel and Quit[]

What is the difference between Evaluation >> QuitKernel and Quit[]? Both seem to quit the kernel (and clearing all ...
0
votes
0answers
52 views

Evaluating Expectation [duplicate]

I would like to have a result equal to a function : ...
0
votes
0answers
54 views

Order of evaluation when using Solve and Minimize

I have to solve numerically an integral, that ends up being more or less as follows: Solve[f[x]==a*Sum[Sin[x-i]*(f[i]-f[i-1]),{i,1,x}],f[x]] (not actual ...
-3
votes
1answer
122 views

Integration with mathematica? [closed]

I am very new to Mathematica. I am trying to evaluate ∫ (1+lnx)Sqrt(1+(xlnx)^2) using Mathematica. I know a substitution must be done so I have set ...
2
votes
1answer
112 views

Mathematica displays the unevaluated expression Expectation function

The evaluation runs for a few seconds and then Mathematica displays the unevaluated expression Expectation function ...
1
vote
1answer
51 views

Getting Gamma as a result for integration [closed]

When finding the mean from the distribution, fx = 4*x^3*Exp[-x^4] meanx = Integrate[x*fx, {x, 0, Infinity}] I get Gamma[5/4] Could someone explain what ...
0
votes
1answer
61 views

Defining a function with algebraic parameters

I am trying to define and use a function to represent the eigenstates of a Quantum Harmonic Oscillator, which have the general form: $$\psi_{n}(x) = \frac{1}{\sqrt{2^{n} n!}}\left(\frac{m \omega}{2 ...
10
votes
2answers
304 views

ScheduledTask with scoped variables. Working with timed evaluation

I guess I have to try harder and focus more but timed evaluation always frustrates me. I will show the issue on simple example of delayed trigger. ...
1
vote
0answers
45 views

Question on Function in Replacement Operation

I am trying to create a replacement function which, depending on the input, gives an additional minus. In my example I have an undefined function a with two ...
6
votes
2answers
475 views

How Can Notebook Know When it Called by Another Notebook?

I would like a notebook to behave slightly differently depending on whether it is evaluated from another notebook; i.e., ...
4
votes
0answers
68 views

Regarding Evaluated True

Done a bit of reading: Normal[Series[ ]] does not give a normal expression Regarding the Evaluated->True, consider: ...
0
votes
0answers
31 views

reloading previously evaluated inputs? [duplicate]

How do I avoid having to resend previously evaluated commands when I reopen my notebook? can't it just allow me continue my computation from where I stopped? Also, some inputs take forever to execute, ...
1
vote
1answer
53 views

How to abort silently?

I want to Abort[] an evaluation without generating this message: $Aborted Is there a way to do this? This messages modifies my notebook, and I don't want this to ...
2
votes
0answers
65 views

$Epilog does not work when exit

The following code does work: $Epilog := Print@1; Quit[]; But if I close the document and exit WM or click QuitKernel, it does not work. Why?
15
votes
1answer
2k views

A one line proof that one is zero using Mathematica 10

a = (Sqrt[2] + 1) (Sqrt[2] - 1) - 1; {a/a, Simplify[a]/a, b/b == Simplify[b]/b} {1, 0, True} This one line "proof" that ...
1
vote
2answers
63 views

Strange behavior of the Evaluate function

I am solving a system of differential equation whose unknown are saved under variable vec={C00,C01,C10,C11} and the solutions are saved under variable ...
1
vote
0answers
53 views

Is it possible to pipe the output of EvaluationMonitor to Excel?

I have an EvaluationMonitor setup to capture the points processed by NIntegrate. This is a case where the same function, integrated over the same region in cartesian coordinates yields a dramatically ...
4
votes
1answer
96 views

Slowdown of Flat attributed function

I was trying to write an associative function f using the attribute Flat. ...
3
votes
0answers
120 views

Dynamic and Refresh

If I am not mislead by my memory, in Mathematica 6 a function Refresh was introduced, having the options UpdateInterval and ...
3
votes
1answer
83 views

Defining a function that prints both the name and value of a variable defined locally within the calling function

To save time when debugging with Print statements, I'd like to define a function -- call it PrintVal -- that prints both the name and value of a variable defined locally within the calling function. ...
10
votes
1answer
294 views

Why does the documentation call functions “pure”?

Clearly, functions in mathematica are not pure functions according to the definition on Wikipedia (no side effects - basically implementabe with table lookups): ...
2
votes
1answer
51 views

Is there a simple function identify the sign of an expression given constraints

I'm looking to find a simple function that can identify the sign of an expression given a set of constraints. I have looked around and do see that there is a few threads on this but I'm not sure I ...
0
votes
1answer
40 views

How can I get numerical answers to integrals involving the error function?

This is the integral I am trying to evaluate in mathematica: Integrate[Exp[-p^2/(m w h)], {p, -Infinity, Sqrt[h m w]}] Can someone show me how to get a numerical answer out of this?
1
vote
2answers
73 views

Assigning to the “local” version of a symbol

Compare Manipulate[c[1] = 1; c[1], {c[1], 0, 1}] with Manipulate[Do[c[i] = 1, {i, 1}]; c[1], {c[1], 0, 1}] The first case ...
0
votes
0answers
28 views

Expanding Function Based on Congruence Classes

I'm trying to get Mathematica to expand $\quad \quad \beta_n=\sum_{r=0}^{n}\frac{\alpha_r}{(q^4;q^4)_{n-r}(q^4;q^4)_{n+r}},$ where $\alpha_r$ is an integer valued sequence that is given by ...
10
votes
2answers
623 views

DSolve cannot solve for certain branches of the solution

Update - This has been fixed in 10.0.0 Could somebody please tell me, why I am always getting an error message when trying to run the following code: ...
3
votes
1answer
66 views

A problem about sorting final result

Three days ago, I asked a question about B-Spline Basis fuction here @Michael E2 given a solution to make the order of interval looks normal The easiest way would be to sort it afterwards: ...
8
votes
3answers
2k views

Keyboard shortcut to evaluate notebook

(If this is entirely trivial, although I couldn't find an answer as much as I searched the archives, I will delete the question.) How could I add a keyboard shortcut to evaluate the entire notebook ...
15
votes
4answers
398 views

Prevent graphics render inside held expression

Assuming each odd line is input I would like the even lines to be the output of the following lines. In the above the Graphics are inside ...