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

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5
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1answer
188 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
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2answers
100 views

Parallel function evaluation for minimal value

I am asking myself, if the evaluation of a function f looking for a minimal value over a discrete set of values can be parallelize (brute scan for a potential ...
5
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2answers
132 views

A pre-parsed HoldForm

HoldForm holds an expression's parsed form not its actual "inputted form" e.g. ...
5
votes
1answer
189 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
1answer
772 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. ...
5
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3answers
254 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
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1answer
45 views

How to understand the different output of two UnsetShared?

Update From technical support, Thank you for contacting Wolfram Technical Support. I understand that you are reporting an issue with UnsetShared deleting the shared variable after a second ...
5
votes
1answer
45 views

How to evaluate following inputs only after finishing CreateDialog

I have a code which starts with the following Cell: ...
5
votes
1answer
362 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
222 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
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1answer
35 views

How could I set TimeConstrained globally?

I want to set TimeConstrained globally, I tried use $PrePrint as bellowed script: ...
5
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1answer
132 views
5
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1answer
88 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
163 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
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2answers
381 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, ...
5
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1answer
119 views

Changes in Handling of Real Zeros

I recently upgraded from Mathematica 5 to Mathematica 8 and I have a number of notebooks that no longer work correctly. The problems relate to the use of units. I don't need complicated unit ...
5
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1answer
977 views

Behavior of expression evaluation in Plot

I'm confused with Mathematica's way of parsing expressions. I've been struggling with this for a while and never found an exhaustive answer, sometimes things don't parse the way I think they would ...
5
votes
2answers
1k views

Speeding up mathematica by subsitituting numerical values

According to this Wolfram Blog post, one can speed up Mathematica code by substituting numerical values as soon as possible. How does one substitute before the main expression is evaluated? The ...
5
votes
1answer
164 views

Force Dispatch to generate dispatch tables

Dispatch creates hash tables only for lists of length larger than 3. Is there any way to force MMA to create hash tables even for lists of length smaller than 4? ...
5
votes
1answer
155 views

how to print stack trace when TimeConstrained times out

According to the documentation, TimeConstrained generates an interrupt which interrupts the computation. This interrupt is treated just like an abort, at least in ...
5
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1answer
47 views

Partial evaluation of symbols with non-inert OwnValues

Background: there are many, many questions here about the infamous ::setraw error. More often, than not, they have to do with repeated assignments to symbols. Here's the code: ...
5
votes
0answers
181 views

Can I define an axiomatic (Boolean algebra) system and prove theorems using Mathematica?

The general question is Can I define an axiomatic system and prove theorems using Mathematica? The more concrete one is about Boolean algebra. I consider this axiomatic Boolean algebra system ...
5
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0answers
127 views

Are there any videos that show how different Mathematica expressions are evaluated?

Are there any videos that show how different Mathematica expressions are represented internally as object graphs and demonstrate how they are transformed during an evaluation? I am asking because I ...
4
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3answers
188 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 ...
4
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3answers
154 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 ...
4
votes
2answers
115 views

Choosing an initializer list in With

I'm trying to have several initializer lists in a With function and choose which one I want to use. So far I have this: ...
4
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5answers
164 views

Using Through with SlotSequence

I have an expression consisting of a few pure functions added together like so: f+g+h I want to add the bodies of these functions together and make that a pure ...
4
votes
2answers
131 views

Simplifying expression with non-commutating entries

Say I have an expression such as (a + X)**(b-Y) where the variables above possess the following commutation relations [a, b] = [a, X] = [a, Y] = [b, X] = [b, Y] ...
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2answers
170 views

When are numerical expressions identical

Very elementary: 2 + 3 == 5 evaluates to True and 5 == 5 evaluates to ...
4
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4answers
1k views

Replace symbols with values without evaluation

If I have assigned values to a, b and c: ...
4
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2answers
296 views

How to define the irrational domain or any other arbitrary domain?

I have found no way to define the domain of Irrational numbers. I can easily define a test to see if a number is irrational by defining: ...
4
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2answers
99 views

Derivative before Numerical Integration

I need to take the derivative of a function that have a numerical integration on it. The variable in which the integration will be taken is not the same as the one in which the derivative will be ...
4
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1answer
360 views

mathematica does not evaluate without internet access? [closed]

I am watching the video Hands-on Start to Mathematica Basic Graphics and for about 15 minutes I was trying to evaluate $\frac{\sin x}{x}$ and each time I encountered errors like: The result can ...
4
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2answers
142 views

Coarse-graining in numerical integrations

I have been working recently in a coarse-graining problem I found when using NIntegrate: I am trying to evaluate the function $$f(a)=\int_0^{\infty}x\,e^{-(a^2+b^2)x^2}\text{d}x$$ numerically as a ...
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2answers
216 views
4
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2answers
78 views

With command does not behave as expected according to its Attributes

The attributes of the With command are HoldAll which means it should not evaluate its arguments before its starts its business. ...
4
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2answers
1k views

How do you configure Mathematica 9 to automatically evaluate all notebooks?

I have a Mathematica 6 course that I am using in Mathematica 9; there is no updated version. Every time I open a notebook I have to go to the Evaluation menu and click on "Evaluate Notebook". Is there ...
4
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1answer
528 views

Can a Table iterator “leak” into a Module?

I want to repeatedly call a module by using a Table statement. When I use an i iterator in the Table command calling the module, I receive the error message ...
4
votes
2answers
107 views

Manipulate in modal mode

It is sometimes convenient to use Manipulate to set up global values which are to be used in the rest of the notebook. In such cases one can select and run the ...
4
votes
1answer
189 views

Can $\it{every}$ usage of While be changed into NestWhile?

Ok, I think this problem is more close to philosophy. :P I've some idea now. But I'm not sure whether it's correct. For the purpose of convenience, I will use some C-like code instead of MMA's. A ...
4
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2answers
146 views

Equivalent of __FILE__?

Many languages define a special identifier whose value is the path to the source file currently being processed. (For example, in C, this is done through the ...
4
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1answer
78 views

How can I kill one evaluator from another?

I have a kernel named A in one notebook and other notebook with kernel B, how can I kill B from A?
4
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1answer
129 views
4
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1answer
171 views

ParallelEvaluate: Evaluation Rules and Increment

I'm trying to understand how ParallelEvaluate works, considering the two following snippets: ...
4
votes
1answer
132 views

Example from Mathematica documentation (ExtremeValueDistribution) seems to be evualting “forever”

I am referring to this example at the reference page for the extreme value distribution: http://reference.wolfram.com/mathematica/ref/ExtremeValueDistribution.html#6764486 The first three commands ...
4
votes
3answers
226 views

How can I create a custom control which evaluates to a list of values or replacements?

I have a set of variables which are used in various places in my calculations (solving a system, initial conditions, etc.). In order to make this easier to deal with, I want to make a control-like ...
4
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1answer
134 views

Pre and Post in a Block[]

Why does Block[{$Pre = ( 1 + #) &}, 1] produce 1 while ...
4
votes
1answer
5k 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 ...
4
votes
2answers
71 views

Append fixed value to random selection of list

(This question might be an application of this other question, but there might be another solution specific to this application that I'm not aware of.) I am currently in a situation in which (in a ...