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
1answer
59 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: ...
2
votes
1answer
128 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
64 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-> ...
2
votes
2answers
62 views

Confused with HoldForm in Postfix notation

Why does the following code produce different result? In my mental model, they should be the same. ...
4
votes
5answers
199 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} ...
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 ...
7
votes
2answers
211 views

Another difference between Set and Setdelayed. Evaluation shortcut?

A little while ago I wondered why f[x_] = f[x] gives an infinite iteration. I ended up discovering the following difference in evaluation between ...
3
votes
4answers
235 views

Replace symbols with values without evaluation

If I have assigned values to a, b and c: ...
0
votes
2answers
209 views

Defining a function in terms of matrix elements

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 ...
15
votes
2answers
725 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: ...
4
votes
1answer
83 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 ...
3
votes
2answers
91 views

Evaluate in Plot leads to function error

Please help - I'm really struggling to understand why this evaluates with errors. ...
0
votes
0answers
13 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 ...
3
votes
1answer
89 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 ...
7
votes
2answers
270 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 ...
4
votes
0answers
128 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 ...
0
votes
2answers
77 views
2
votes
1answer
105 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
115 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 ...
12
votes
4answers
339 views

Elegant high precision `log1p`?

Sometimes it is hard to understand how numerical expressions are evaluated. I remember reading claims by Wolfram on how smart the Kernel is to evaluate expressions trees numerically by recognizing ...
3
votes
2answers
91 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
77 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
79 views

Need to run evaluation 2 times

Why does this only work after running the evaluation 2 times? ...
2
votes
1answer
69 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
2answers
117 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 ...
3
votes
3answers
107 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 ...
4
votes
1answer
134 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 ...
10
votes
1answer
102 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 ...
1
vote
1answer
94 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 ...
6
votes
2answers
109 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, ...
2
votes
1answer
72 views

Differentiating a function that has NIntegrate within it

I am something of a novice with Mathematica. I have written the following code; ...
7
votes
1answer
181 views

ScheduledTask with scoped variables. Working with timed evaluation

I guess I have to try harder and focus more but timed evaluation always frustrates me. I will show the issue on simple example of delayed trigger. ...
8
votes
3answers
181 views
0
votes
1answer
99 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. ...
10
votes
3answers
158 views

Creating a custom context with a Hold construct

I'm trying to create a function "InContext" to execute a piece of code inside a certain context (and to return the result of evaluating that piece of code). One approach is to place the code inside a ...
5
votes
2answers
148 views

Remove versus ClearAll

What is the difference between Remove and ClearAll? I thought that "not being recognized by Mathematica", which is the effect ...
2
votes
3answers
114 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 ...
1
vote
1answer
100 views

Caching data in Mathematica package

Consider the following: m=Quantity[1,"meter"] If I run the package, it will return 1m But when I load the package, the ...
1
vote
1answer
98 views

Evaluation of second argument to NIntegrate

Apologies if this is a duplicate, but I couldn't find it. The expression Integrate[x^2, Flatten[{{x},{1,2}}]] evaluates properly, to $\frac{7}{3}$. However, ...
0
votes
1answer
138 views

Plot[ D[Sin[x]] ] and Evaluate[] [duplicate]

Why does t = 2 Pi; Plot[D[Sin[x],x], {x,0,t}] (* Plotting the derivative of Sin[x] *) not work, but ...
17
votes
1answer
367 views

Incorrect result from Integrate

I attempted to calculate the following integral: ...
1
vote
1answer
105 views

Printing intermediate calculations in an external file, while suppressing the output in the notebook

I'm trying to construct a text-file that contains all the operations that Mathematica performs when evaluating an expression. However, i'd like to suppress all output in the notebook in which I'm ...
7
votes
3answers
203 views

Why does Mathematica not seem to know that $i^x$ cannot be equal to $0$?

I am experiencing a curious behaviour of Simplify when handling expressions involving powers of $\mathbf{i}$, such as $\mathbf{i}^x$ where $x$ is unknown. For ...
1
vote
1answer
132 views

Passing a joined list of symbols for Module or Block to treat as its own local symbols

The Question I'd like to write a function which itself takes a list of symbols, e.g. Foo[{x, y, z}] to pass to Module ...
2
votes
1answer
354 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. ...
0
votes
1answer
84 views

Plot producing many error messages when given complicated function

I'm new to Mathematica and am running in to all sorts of silly difficulties with coding in it. I'm trying to calculate a function f[x, k], normalise it with another ...
2
votes
1answer
198 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: ...
5
votes
1answer
119 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 ...
11
votes
4answers
291 views

Using With to scope over pure functions

Consider this example: given an option for a function func as "x" :> (a&), how can one assign different values to ...