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

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6
votes
2answers
105 views

Force evaluation of the right-hand side of a local variable definition

One can do expression = a + 1; f[a_] := Evaluate[expression] but how would one do something like this ...
6
votes
2answers
209 views

There is an issue with Manipulate in which it updates its argument twice in V10

I have asked this question before (here) and I thought that the issue is only when moving the Notebook window. It appears that Manipulate is working in weird manner. ...
6
votes
2answers
124 views

Showing “updating…” message while Manipulate is re-evaluating

Is it possible to show a fixed text such as "updating..." instead of the last result shown, when Manipulate is re-evaluating an expression (in a slow evaluation ...
6
votes
1answer
223 views

Machine Epsilon

I'm trying to evaluate the machine epsilon of my computer (see below). I wrote this: ...
6
votes
1answer
111 views

Why do certain fractional values in TriangleWave not evaluate?

While answering another question I discovered that TriangleWave does not automatically evaluate when given certain fractional values, specifically fractions with a ...
6
votes
1answer
290 views

How to simplify expression and use HoldForm at the same time?

Hopefully a simple problem for the experts here. I have a need many times to build a symbolic expression for an equation (say a PDE) to use for plot labels in a low level function inside ...
6
votes
1answer
70 views

How to force evaluation of an expression with Part left unnevaluated?

My goal is to minimize a real valued multi-variable function averageFreeEnergyDensity. The function accepts an integer argument ...
6
votes
1answer
508 views

Resume/continue interrupted evaluation

I interrupted an evaluation to quickly do something else. How do I resume the interrupted evaluation? I cannot open the "Interrupt evaluation" window, as it is disabled. There is no "Resume" button to ...
6
votes
1answer
234 views

Functional-Style Partial Application and the Accumulator Pattern?

Following up on Functional-style Fixed-Length Queue Object?, I want to generalize it to a functional-style accumulator pattern. Lots of things look like accumulators, loosely defined as binary ...
6
votes
1answer
398 views

PlotStyle does not work when plotting a non-evaluated list of functions [duplicate]

When a list of functions is passed to Plot in an unevaluated form (e.g. with Through), the result is a plot with single color. ...
6
votes
1answer
207 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 ...
6
votes
1answer
708 views

Evaluate while external command is being run [duplicate]

Possible Duplicate: Computing Many Slow I/O Operations I'm launching an external command with the Mathematica front end that takes two arguments: ...
6
votes
1answer
260 views

Context “Unique to This Notebook” makes variables black even if they're not defined?

I'm trying to use this technique to keep variables separated between different notebooks. It seems to be working fine, except that variables turn black as soon as they are evaluated — any ideas why ...
6
votes
0answers
168 views

Built-in symbols which are more close to the root/core of Wolfram Language

Seeing the vast scope of science covered by the Wolfram Language (WL) and the large amount of built-in symbols (functions), I am curious to know which built-in symbols are more close to the root of ...
6
votes
0answers
102 views

What is the difference between GenerateDocument and TemplateApply[NotebookTemplate[

Edit 5. X 2015 I don't see any reason why that cell is evaluated. And I don't see how my opinion may change with small update of docs like suggested by support: I have not heard back from the ...
5
votes
5answers
246 views

How to make a table of $\sum_{i=1}^n$?

I want to create a table of $\displaystyle \sum_{i=1}^n i^k$ for $1\le k\le 5$. The output I want to obtain is a TeXForm output as follows. \begin{align} ...
5
votes
3answers
261 views

First evaluation fails

I am fairly new to Mathematica (version 7), so please bear with me... I have duplicated, in Mathematica, a program that I originally wrote in C (it generates OEIS sequence A191837). The problem is ...
5
votes
5answers
204 views

Nested function with an increasing argument

If, for example, I have a nesting function like Nest[1 + x^n (#) &, 1, 3] it gives the result ...
5
votes
3answers
3k views

How to force 2+2=5

I was looking at this question (writing a program such that 2 + 2 = 5) and tried to write something in Mathematica, but I couldn't get something to work without completely replacing ...
5
votes
3answers
70 views

StepMonitor won't display Plot

This example is from the documentation under Monitor ...
5
votes
3answers
428 views

Why the difference?

When I do the double sum using the sigma notation I get $$1 + \sum_{n=0}^{\infty}\sum_{k = n}^{\infty} \frac{1}{(k+2)k!}$$ $1 + e - \cosh[1]$ When I do the sums as below, I get the expected ...
5
votes
2answers
129 views

ReplaceAll performance problem: packed arrays on the LHS are unpacked when the RHS is too long

The following is one of the most mysterious performance problems I encountered and came up while extending the booleval function mentioned here. I am looking for a ...
5
votes
2answers
229 views

Remove versus ClearAll

What is the difference between Remove and ClearAll? I thought that "not being recognized by Mathematica", which is the effect ...
5
votes
1answer
109 views

“And” to continue evaluation after “False”

Below, is it possible to print No and have x be 2. That is, I'm looking for an And-like function that looks at all arguments ...
5
votes
4answers
134 views

How to map Unevaluated over a list

I have a list {a1, a2, ...... , an}, in which all as have been initialized to a number. I want to get: ...
5
votes
2answers
243 views

Associativity of `/@` [duplicate]

Why are the following not equivalent: Map[Line, Map[(Print[#]; #) &, {{{2, 1}, {1, 1}}, {{-2, 1}, {3, 1}}}]] which produces ...
5
votes
3answers
262 views

difficulty abstracting the OptionValue pattern

I am building lots of functions that use Options and OptionValue and wanted to reduce the redundancy in the expressions that ...
5
votes
2answers
778 views

How to make a function that evaluates an expression?

I'm trying to make a function where the input is an expression, but somehow it just won't be evaluated. For example, this little function doesn't work: ...
5
votes
1answer
443 views

Strange Error in Bifurcation Diagram:

I am attempting to plot the bifurcation diagram of the tent map $$ f(x):=2\alpha \begin{cases} x, & 0<x<1/2\\ 1-x, &1/2<x<1, \end{cases} $$ i.e., the plot $\alpha$ vs. the limit ...
5
votes
1answer
239 views

Parts of Module body evaluated in external scope?

I have an expression that suggests that some expressions in a module body are dragging in definitions from outside the scope in a surprising way. First, consider a symbolic constant, ...
5
votes
3answers
346 views

HoldFirst and inserting additional options into a Grid of Graphics

This is related to my earlier question, but is specific to an issue I have encountered with the use of the HoldFirst First, let's create some fake data for ...
5
votes
2answers
123 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 ...
5
votes
2answers
269 views

Why doesn't Evaluate appear to work in this RegionPlot example with MatchQ?

I am trying to plot the region over which a function of two (real) parameters a and b is real-valued, using ...
5
votes
2answers
841 views

Expression evaluation inside of FindRoot inside a Compiled Function

I'm trying to get some performance increase out of my own implicit differential equation solver using Compile[]. The uncompiled function is of the following form: ...
5
votes
4answers
617 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 ...
5
votes
2answers
162 views

Evaluate notebook from other notebook

I have a notebook ("notebook 1") which in the beginning sets some parameters, does something depending on their value and saves the result to a file, say: ...
5
votes
3answers
846 views

Prevent Mathematica to automatically evaluate Manipulate at start

I'm using an initialization cell to import a lot of data: data = Import[myFiles]; and then I use a custom function to display this data with Manipulate: ...
5
votes
2answers
366 views

Manipulate Evaluation Order Problem

I seem to be getting some unintended results from a nested Manipulate that I have not been able to resolve. I boiled down the problem I'm having to a simplified ...
5
votes
1answer
186 views

Impossible to bypass evaluation on returned values?

Following all the great advice on this other question, I'm now fluent with HoldAllComplete and Unevaluated on the input side of ...
5
votes
2answers
131 views

A pre-parsed HoldForm

HoldForm holds an expression's parsed form not its actual "inputted form" e.g. ...
5
votes
1answer
186 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" ...
5
votes
3answers
248 views

Applying a function with the HoldAll attribute inside NestList

I'm trying to write an update function, which can be applied to a list and then to NestList it. As the function has to manipulate the given variable I figured I ...
5
votes
2answers
252 views

Graph does not evaluate some options when not displayed

How can I force Graph to evaluate all its options without actually displaying the graph itself? Evaluating the following code ignores the ...
5
votes
1answer
344 views

Evaluation order control

This question is related to Evaluation order of Button[]'s action Concusion was, Button[]'s actions are evaluated in preemptive link so "the code that needs ...
5
votes
1answer
221 views

Why does Dynamic output cause CPU usage when onscreen?

I write such a line in Mathematica: {Slider[Dynamic[s]], Dynamic[f[x_] := s*x]} After evaluation, the CPU immediately runs at full power. And if you scroll the ...
5
votes
1answer
33 views

How could I set TimeConstrained globally?

I want to set TimeConstrained globally, I tried use $PrePrint as bellowed script: ...
5
votes
1answer
113 views
5
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1answer
81 views

Prevent evaluation of certain cells / code segments

I´m not quite sure if I ask a stupid question but I could not find an appropriate answer in the forum... I have a variety of cells (= code segments) in my notebook which I would like to evaluate in ...
5
votes
2answers
162 views

Strange Behavior when making Equal Listable in Pick

While trying to make this problem more efficient I tried different methods and dabbled with making Greater and Equal ...
5
votes
2answers
365 views

Problem with ParametricPlot of multiple Curves

I have written a function f[Ne,t,T], that gives back a list of results when evaluated with numeric values of the variables Ne, ...