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

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3
votes
0answers
171 views

A design of abstract data structures: How robust is the presented design? [closed]

EDIT: An envisioned answer to this post should be in the form of a mathematica code that can demonstrate how the internal checks discussed below can be bypassed. Everything goes... On my part, I think ...
3
votes
0answers
63 views

Non-preemptive evaluation of a dynamic function? [duplicate]

I want to monitor a long calculation that is triggered by the release of a Slider. While one can indicate running calculations when the main evaluation loop is ...
3
votes
0answers
327 views

A is fast, B is fast, but together they're Mathematica-crashing slow?

I'm trying to do something with finding solutions to a quantum mechanics problem with n wells. If there are 40 wells, I need to find the solution to an equation in the form: ...
2
votes
3answers
167 views

will the same result be evaluated twice per evaluation?

here is the silly question of mine, if mathematica takes 3 seconds to evaluate the function ...
2
votes
2answers
131 views

How to make Mathematica returns the exact expression I typed

I'm using Mathematica to compare some constants. Before playing around with those constants, I would like to check that I didn't make any mistake in typing them. So my question is the following: "What ...
2
votes
1answer
204 views

Nested Derivative

These two expressions are mathematically the same, but when substituting with the same rule, yield different results. What is happening? ...
2
votes
3answers
311 views

Select sublists with second element nearest to zero

I've got some big lists from which i need some data (one of the big lists). To be specific, I need to divide this biglists in sublists of the same length (10000), and form a new list with the mean of ...
2
votes
2answers
3k views

Step-by-step definite integration

I am interested in obtaining the intermediate steps for rather straightforward symbolic definite integrations (e.g., from an elementary calculus text). As an example, for $\int_0^1 x\,dx$ I'd like ...
2
votes
3answers
118 views

Dynamic plot with Evaluate on expression

I'm trying to make a make a plot of a table of expressions, which should be pre-evaluated (since they are infinite series with analytic sums). I'm able to make the plot normally with ...
2
votes
2answers
94 views

Handling a sequence of unevaluated arguments

I have the following piece of code: ...
2
votes
2answers
124 views

Time delayed evaluation of a function

I'd like to write a function that delays the evaluation of a function (say) $5$ seconds after I hit Shift+Return. Is this possible?
2
votes
2answers
170 views

Expectation of a family of random variables

I did some search here, but seems that no one asked about this. I want to define a family of independent and identically distributed random variables, $x_1,...,x_n$, and then calculates the expected ...
2
votes
2answers
90 views

Merging two held expressions into a held compound expression

Consider e1 = Hold[a = x + x; b = y + y + y]; e2 = Hold[c = a + a + b + b + b; c^2]; How can I obtain the following? ...
2
votes
1answer
115 views

Strange results of definitions using OwnValues

I am asking this question simultatenously with this one, which is strongly related. I was trying to see if I could create the behaviour as in that question without using ...
2
votes
2answers
155 views

While loop doing cell evaluation not completing

I am trying to get a loop structure using While to repeatedly evaluate another cell referred to in its body (using a cell tag). ...
2
votes
2answers
186 views

Evaluating Polynomials at Grid Points

I am continuing my quest on B-splines. The code below builds a 5x5 matrix out of B-splines, using the BSplineBasis[] routine. I now want to evaluate the polynomials that are stored in each matrix ...
2
votes
2answers
159 views

Updating a tracked symbol inside Refresh?

I have some code inside a Manipulate, whose goal is to allow the user to edit the upper half of the matrix while keeping it symmetric at all time. The minimal code ...
2
votes
2answers
1k views

Animation of Differential Equations from NDSolve with ParametricPlot3D and Evaluate

I have a system of differential equations (referred to as "s") and use NDSolve to obtain the solution. I substitute the interpolated functions for the original ...
2
votes
1answer
664 views

A combination of Set::setraw and Set::shape errors

Please consider the following toy code: ...
2
votes
1answer
80 views

Need to run evaluation 2 times

Why does this only work after running the evaluation 2 times? ...
2
votes
1answer
208 views

Expectation function does evaluate my expression

I am trying to evaluate the expression Expectation[(B x (-6 b + 12 a n0 + B x + B^2 x^2))/(2 (6 a + B x + B^2 x^2)), Distributed[x, BetaDistribution[α, β]]] ...
2
votes
1answer
81 views

ParallelEvaluate: Evaluation Rules and Increment

I'm trying to understand how ParallelEvaluate works, considering the two following snippets: ...
2
votes
1answer
68 views

Defer parts of the expression

Is there a way to Defer only parts of the expression? For example, I have a=1; and then I want the expression to be shown as...
2
votes
2answers
63 views

Confused with HoldForm in Postfix notation

Why does the following code produce different result? In my mental model, they should be the same. ...
2
votes
1answer
375 views

Is there anything like a C pointer (or returning a reference) in $Mathematica$?

I want to do in Mathematica what the following does in C. ...
2
votes
1answer
256 views

Evaluate Numerator and Denominator Separately

I have this function. ...
2
votes
3answers
148 views

Function to preserve evaluation on display?

I'm looking for a function that applies the following behavior to an expression: -When the expression is given as the full input, or as part of a function that cannot be evaluated, it remains in ...
2
votes
1answer
2k views

setting a variable equal to the output of FindRoot

So I set a function f[x] f[x_] := x*E^(-x) - 0.16064 Then I set a variable 'actualroot' to the function FindRoot, starting at 3 ...
2
votes
1answer
94 views

How to explain the behavior of Rule inside these functions [duplicate]

I'm trying to define a function that takes an expression and spits out a pure function involving a replacement rule of that function's variable. An example would be a function ...
2
votes
1answer
207 views

Why is this expression being held, and how can I evaluate it?

I can't figure out why an expression isn't evaluating, even though there's no Hold* in its FullForm: ...
2
votes
1answer
174 views

Manipulate executes expressions multiple times

I am using Manipulate for a rather intricate front end for data visualization. I was getting very sluggish performance and was able to boil the problem down to a ...
2
votes
1answer
258 views

Use output of NDSolve as an integration limit of NIntegrate

I've been working on a ODE, for a function y[t], that, due to it's complexity, has to be solved numerically. I then need to use the results of NDSolve, which I ...
2
votes
3answers
399 views

GraphPlot only working when I evaluate twice

I have some code that builds a graph and some vertex coordinates, but when I evaluate it I get a message that the list of coordinates is not valid and the graph is not valid and it shows the output as ...
2
votes
1answer
48 views

Inactive derivative: extract constants

I have a problem with an unevaluated derivative. In the example code below, i need the integration wrt to y be evaluated, while the differentation wrt x needs to stay unevaluated. I see the point that ...
2
votes
2answers
52 views

Order of Evaluate for Map

I would like to get a list of variable names as strings. For example, x = 1; y = 2; Map[SymbolName, Unevaluated /@ Unevaluated@{x, y}] {"x", "y"} This works ...
2
votes
1answer
99 views

Wrapping at evaluation for inline cell

I've been playing with inline evaluation and I've came to the conclusion that it's most convenient to put the Dynamic@ inside the inline cell, so I've started to ...
2
votes
2answers
72 views

Can I have Mathematica show intermediate forms before final evaluation?

If I have x = 2 and I want to evaluate y = x^2 I would like to the output to show ...
2
votes
1answer
38 views

is there a way to construct a pattern that would trigger when an expression is used as a held/unevaluated in some form?

For example, consider the following code f[x_] := (Print["evaluated f"]; workWith[x]); We use it, then f evaluates: ...
2
votes
2answers
354 views

Integrating a Simple Piecewise Function

If I define f[x_]:=If[x<0,-1,1] and then integrate,say Integrate[f[x],{x,-3,7}] I get what I expect, namely 4. But ...
2
votes
2answers
132 views

Generating an editable table that can be used as input

Say I have a number $n_{max}$. I want a command to generate a table like 1 1 2 2 3 3 4 4 ... nmax nmax where the second column is editable, and this table can be ...
2
votes
1answer
119 views

Need help looping a notebook evaluation

I'm a new user and would like to find the minimum value of soln1[30] obtained after repeating the following evaluation (below) for 1000 cycles (for instance). I can obtain sequential values of ...
2
votes
1answer
79 views

Differentiating a function that has NIntegrate within it

I am something of a novice with Mathematica. I have written the following code; ...
2
votes
1answer
49 views

Label cell goes away with SelectionEvaluate

When a given cell has a label (given with the CellLabel->"label" option of the cell), then this label disappears after calling SelectionEvaluate[ nb ] when the ...
2
votes
1answer
151 views

Dynamic [ NotebookEvaluate [“_”] ]

A nice way to centralize various tasks in one notebook is the NotebookEvaluation function. For instance I can evaluate ten notebooks from a single notebook (e.g. ...
2
votes
1answer
103 views

Reuse local variable in declaration within With [duplicate]

Considering the richness of Mathematica.SE, I am quite surprised I could not find my answer... I am very sorry if it is a duplicate. Consider the following example: ...
2
votes
1answer
178 views

is there a method to send different cell evaluation to different core

I am running Mathematica on a computer with mulicpu and every cpu has multicore. I am wondering if there exist a method to send different cell evaluation to different core? So if I already have a ...
2
votes
1answer
109 views

NotebookWrite undo

Is there way to make NotebookWrites undooable? For example let's say I open a new notebook and then run. ...
2
votes
1answer
95 views

kernel Local crashes during the course of a For loop

I want to find the minimum of the function r[x,p] subject to the constraint w[x,p,t]==0 (t ...
2
votes
1answer
244 views

Why does Mathematica evaluate Sin[2.0] but not Sin[2]?

I can't understand why is it that In[88]:= Sin[2] Out[88]= Sin[2] while In[89]:= Sin[2.0] Out[89]= 0.909297 I even tried ...