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

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13
votes
2answers
162 views
1
vote
1answer
44 views

Cell seems to be evaluating in exponential time even though it shouldn't

I am trying to implement Newton's method for a given function f[x] and a starting x-value xval. The code should print out each new x-value as it approaches one of the zeroes of the functions. g[x] is ...
15
votes
2answers
207 views

How to find out what files are touched when Get is called?

Is there a way to capture all package files touched whenever a package is called via Get, Needs, ...
0
votes
2answers
421 views

Defining Piecewise Functions in Modules

In short, my question is the same as my previous one except that everything is now wrapped up in a module. The relevant code I'm working with is: ...
3
votes
1answer
152 views
4
votes
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-> ...
6
votes
2answers
189 views

Partial result of aborted evaluation of FullSimplify

When FullSimplify invoked on a large expression, it can run for hours. If I do not have time to wait, and abort the evaluation, I get no result, although, ...
9
votes
1answer
137 views

Why does $Failed have attribute HoldAll?

Why does $Failed have attribute HoldAll? Are there typical situations where $Failed is ...
2
votes
2answers
250 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 ...
3
votes
1answer
1k 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 ...
0
votes
1answer
651 views

Pass unevaluated function with evaluated arguments

I am almost sure that this question has been asked somewhere. I found similar ones, but I cannot find exactly what I need, which might mean that I am on the wrong track. I search a method to pass an ...
4
votes
2answers
308 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: ...
3
votes
2answers
168 views

Bare symbol invocation fails but not if used with an argument

How to achieve the following behavior on a symbol f? Background: The main goal is to use the symbol to tag an abstract data structure where downvalues are used to store information. Only defined ...
1
vote
2answers
639 views

Converting expression into string without evaluating it

How can one convert a Mathematica expression into a string without the expression being evaluated first? I tried using Hold, but it returns ...
7
votes
2answers
257 views

Evaluation in lambda function

If I have a function, that returns a function, for example: f[a_] := a^2 * # & then f[3] == 3^2 # & Is there a way ...
2
votes
1answer
380 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. ...
11
votes
3answers
1k views

Every second evaluation in notebook front end is slow

I'm having a rather baffling problem that Wolfram was unable to help me diagnose, and I'm hoping one of you geniuses in residence here can figure it out. (I don't get access to the Technical Support ...
7
votes
1answer
88 views

How to reset the $ModuleNumber?

According to the documentation, we can reset $ModuleNumber to a positive machine integer. There is even an example in the doc: ...
5
votes
1answer
840 views

Order of operations, precedence in Mathematica [duplicate]

I get confused in the order of operations in Mathematica. For example, f /@ 10^{1, 2, 3} {10, 100, 1000} In my head, that ...
0
votes
1answer
205 views

Not evaluating all cells unless I explicitly evaluate each one?

I'm running a Mathematica (version 8) notebook. In one of the first few cells, it is supposed to plot some data. It uses a couple functions that are defined in an above cell. If I do Evaluation-> ...
3
votes
2answers
103 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
125 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 ...
4
votes
4answers
1k views

Replace symbols with values without evaluation

If I have assigned values to a, b and c: a=7; b=5; c=6; ...
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 ...
2
votes
1answer
327 views

Skip one step of the loop if there is an NIntegrate::eincr message

Is there a possibility of skipping one step of a loop if in this step there appears an error like NIntegrate::eincr? After skipping, the loop should go to the next ...
0
votes
2answers
2k views

Defining a function in terms of matrix elements [closed]

Currently trying to use elements from a matrix in defining a function however having some trouble. This is a somewhat simplified version of the problem. Say I have the matrix ...
16
votes
2answers
1k views

Why do certain values in ArcSin not fully evaluate?

This is a continuation of: Why do certain fractional values in TriangleWave not evaluate? The analysis by R.M and rasher revealed that problem to reduce to the behavior of: ...
3
votes
2answers
192 views

Evaluate in Plot leads to function error

Please help - I'm really struggling to understand why this evaluates with errors. ...
0
votes
0answers
19 views

Evaluating a String that is a Variable [duplicate]

I have a Variable assigned a value, say ImportantDocuments=1 How do I make N["ImportantDocuments"] evaluate to be 1 instead of ImportantDocuments I found that N[...
9
votes
2answers
380 views

Understanding Villegas-Gayley

Temporary message: I have written another question about the behaviour the code by Oleksandr R. . Sadly I clicked "discard" and that was lost. I am a bit demotivated now and in order to not let the ...
3
votes
1answer
127 views

Why is held expression evaluated?

Context: I'm studying non-linear dynamics. As part of a bigger problem, I'd like to generate lists of the form {{deq, ic1}, {deq, ic2}, ...}, where ...
4
votes
0answers
273 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 ...
5
votes
1answer
382 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 ...
2
votes
1answer
249 views

Piecewise function with user-input interval

I would like define a function g[data,bins,x] which is a piecewise constant function taking value data[[i]] in the range ...
2
votes
1answer
146 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 soln[...
3
votes
2answers
181 views

Keep data in memory inside a notebook without having to evaluate it again [duplicate]

I have a notebook that calculates some data in a relatively large time so I want to keep these data saved inside the notebook without recalculate them every time I open the notebook. I know I can ...
0
votes
3answers
98 views

Preventing evaluation until all undefined symbols are resolved

FixedPoint[If[# <= 0, 0, # - 1]&, 2 x] Causes an infinite loop because of 'x'. How do i automatically prevent evaluation until ...
2
votes
1answer
83 views

Need to run evaluation 2 times

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

Manual CellGrouping option causes crash at cell evaluation

Update: Try to reproduce this behaviour with CellGrouping set to manual. To do that: either evaluate ...
10
votes
1answer
124 views

Aborting from inside a ScheduledTask

If you have an Abort[] inside a ScheduledTask expression, what does it abort? The scheduled task evaluation, or any main kernel ...
2
votes
1answer
73 views

Evaluate only one from a set of procedures

Let's say I've got a list of procedures: {Print[1];, Print[2];, Print[3];} And I want to only evaluate 3rd one: ...
3
votes
3answers
140 views

Using a variable to tell Mathematica which existing variable to manipulate

I have an estimation routine I have coded up, I want now to do some tests on it where I pick a particular parameter and run the estimation for differing values of that parameter. What I want is to be ...
3
votes
2answers
199 views

Assigning an equation as a variable

I am compiling a calculator where many slider parameters are used to define a value, where the defined value may then be reused to define another value. I am unable able to, or at least been ...
2
votes
1answer
189 views

Differentiating a function that has NIntegrate within it

I am something of a novice with Mathematica. I have written the following code; ...
10
votes
3answers
326 views

How to exit from the innermost enclosing pure function?

Here is what I tried to do: Scan[Function[x, Scan[Function[y, If[y == 2, Return[]]; (* Do something useful *) Print[y]], x]], {{1, 2, 3}, {4, 5, 6}}] ...
0
votes
1answer
158 views

Solving NLODE with substitution

I am trying to get a solution to a non-linear ODE, below is the code that works for my problem. ...
11
votes
1answer
280 views

TimeConstrained dynamic change of maximum time

I would like to run a time consuming function: TimeConstrained[f[x],maxseconds] and be able to change maxseconds during running (increasing or decreasing max ...