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

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2answers
80 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
551 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 "Table:...
4
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2answers
109 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
198 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
votes
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
145 views
4
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1answer
175 views

ParallelEvaluate: Evaluation Rules and Increment

I'm trying to understand how ParallelEvaluate works, considering the two following snippets: ...
4
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1answer
133 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
229 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
138 views

Pre and Post in a Block[]

Why does Block[{$Pre = ( 1 + #) &}, 1] produce 1 while ...
4
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1answer
6k 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
78 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 <...
4
votes
1answer
169 views

Identical code, different answers?

I'm having some trouble with identical code giving different answers. On a fresh kernel (MM 9.0.0.0, Windows 64-bit), running the same code, copy-paste, gives two different answers: ...
4
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1answer
126 views

Stop TradtionalForm evaluating expression

I'm trying to get this expression to display as typed instead of evaluating the 1/1.121. ...
4
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1answer
133 views

Tweaking Prime[n] to return 1 when n==0

I manually evaluate this cell to set Prime[0] Unprotect[Prime] Prime[0] = 1 Protect[Prime] I manually evaluate this cell to reset Prime[0] ...
4
votes
1answer
260 views

Assumptions seem not to be considered

In the following a,b is a probability distribution, i.e. a+b==1 with ...
4
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2answers
62 views

Controlling evaluation in a custom summation function

I'm doing some computations that involve summations with many indices over the same range - consider the simplified example Sum[a[i,j],{i,1,2},{j,1,2}]. To prettify ...
4
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4answers
120 views

Working with ScheduledTasks inside DynamicModules

I have a question - is it possible to run ScheduleTask[] inside DynamicModule[]? What I have tried so far: ...
4
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1answer
53 views

How to adapt MSPToExpression function in $PrePrint?

I am introducing the mathematica Security (MSP module) to our system. The Document suggests use MSPToExpression as followed: ...
4
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1answer
69 views

How to define an expression which is differently evaluated in calculations and printed

Let's say, we have a list: values = {1.2, 0.04, 0.9}; Is it possible to replace 0.04 by some expression, which displays as <...
4
votes
2answers
69 views

How to print unevaluated arguments in the form they were originally typed in?

I'm looking for a way to print a function's arguments, not only unevaluated, but also in the way they were originally typed in. By way of experimentation, I tried stuff like this: ...
4
votes
1answer
128 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. ...
4
votes
1answer
165 views

ExampleData menu view

I'm trying to build an ExampleData browser, so that the "collection"/"type" is selectable in a drop down menu, and the "name" is selectable in another drop down menu. What I have so far: ...
4
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1answer
74 views

Apply a function to the current selection in place

Say a have the function foo: foo[x_] := x + 2 Like the Evalution ...
4
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1answer
2k views

What do the hashtags represent in the result of Solve, and how should I use them? [duplicate]

There is a function that I'm trying to get the inverse of. My function is a simple polynomial: Tn[T_] := 4/9 T^3/Tc^2 + 5/9 T Now I tried to find ...
4
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1answer
334 views

Is there a way to force Mathematica 8 to expand $z^{a+b}$ into $z^a z^b$?

The function PowerExpand[z^(a+b)] does not transform $z^{a+b}$ into $z^a z^b$. Is there a way to force Mathematica 8 to expand $z^{a+b}$ into $z^a z^b$? In this ...
4
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2answers
405 views

Overloading conjugate operator for a particular function

I trying to modify the behaviour of the built-in Conjugate[] operator on a particular function I have defined, to take into account that some of its variables are ...
4
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2answers
379 views

Evaluating a Recursive Expression

Why does this raise an error ...
4
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2answers
210 views

Setting a lower limit on calculation time

Sometimes it can come in handy to set a lower limit for a calculation. Consider for example an animation that is generated by some infinite loop, which would run way too fast to display properly for ...
4
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1answer
52 views

Difference between Initialization Cell and Group

Is there a difference between setting a Cell or a Group of cells to be an Initialization Cell...
4
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1answer
153 views

Why even try the semantic constraints, if expression can't match the pattern structure?

This result is unexpected: Trace[MatchQ[{7}, {_?NumberQ, __}], NumberQ] (* -> {{NumberQ[7], True}} *) Why evaluate NumberQ...
4
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1answer
97 views

Where do Mathematica's probability functions draw a line in the sand for predicates?

Thinking about a recent question mis-posted here (belonged on math), I noted the following. A contrived example - probability that a or b are 1: ...
4
votes
1answer
155 views

How can I test properties of a symbol without unwanted evaluation

Problem How to get the head, size, dimensions, etc. of a symbol without evaluating it? Since Mathematica does not allocate fix storage space and type to symbols it is not trivial to query runtime ...
4
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1answer
73 views

Strange behavior of ArcTan [duplicate]

I've noticed a strange behavior of Mathematica's ArcTan function with two arguments. If both arguments are 0 or ...
4
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1answer
107 views

Formal Differentiation

I'm trying to formally differentiate an expression. (I am aware of how to differentiate formally?, but am unable to generalize the idea) For example: ...
4
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1answer
101 views

Slowdown of Flat attributed function

I was trying to write an associative function f using the attribute Flat. ...
4
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1answer
143 views

Selecting expressions from a sequence that are not subexpressions of earlier elements

I have a While loop that generates and prints an expression on each iteration (there can be thousands of iterations). UPDATE: Some expressions are generated in ...
4
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0answers
91 views

Simple arithmetic with Irrationals fails [closed]

While solving a simple puzzle that asked for a few calculations in plane geometry, I ended up with this expression: $-\frac{55}{2}+\frac{\sqrt{27233}}{2}+\frac{1}{2}(55-\sqrt{27233})$ Or, in ...
4
votes
0answers
119 views

Why the flat f[x] is treated as ghostHead_[f[x]]?

While reading this answer I feel confused. If we do not care any specific detail of the original question, then ybeltukov's answer essentially makes use of the following fact ...
4
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0answers
83 views

Regarding Evaluated True

Done a bit of reading: Normal[Series[ ]] does not give a normal expression Regarding the Evaluated->True, consider: ...
4
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0answers
1k views

Is there a way to stop evaluation immediately? [closed]

Sometimes I'll have a loop that I accidentally made too big. I'll evaluate, and MM will try to run through the entire loop. The program itself doesn't actually seem frozen... I can go to Evaluation-> ...
4
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0answers
272 views

DynamicModule, SaveDefinitions and global functions

Unfortunately, I had not checked stackoverflow, because there, the exact same behavior was already reported. Please see the Q&A "SaveDefinitions considered dangerous". Up-front, I'm on Ubuntu ...
4
votes
1answer
228 views

Manipulate a Plot that contains a variable that contains symbol [duplicate]

This snippet mm = m Manipulate[{mm, Plot[mm x, {x, 0, 1}]}, {m, 0, 1}] (m is not defined anywhere) produces a sadly fixed ...
4
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0answers
534 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: ...
4
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0answers
87 views

Problem with inequality using refine

I am using inequalities to follow some line of reasoning in Mathematica and I came across a problem I can not explain to myself. Does from a>=0 and b>=0 not follow a+b >= 0? How does Mathematica ...
3
votes
3answers
594 views

Help on evaluation control?

I want to plot series of slopes: x, 2x, 3x, 4x, 5x, 6x... I'm trying to do this: ...
3
votes
2answers
308 views

Efficiently evaluating a held expression directly from a list

I am able to evaluate a held expression that I have put on a list by: ReleaseHold[expressionList[[1]]] and ...