# Tagged Questions

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

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### Expression for evaluating multiple functions?

I am constructing 3D data points for a plot and corresponding to specific conditions "manually". I define the values of five parameters [these I always have to define myself]. From those, I evaluate ...
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### How to Plot a function that returns multiple values? [duplicate]

I have a function that returns multiple values, like this: f[x_] := ( (*... something ... *); {y1, y2}); They are computed together, so there's absolutely no ...
371 views

### Replacing parts of a held expression with held parts of another expression

I'm applying the Trott-Strzebonski technique in order to replace inside a held expression. ...
1k views

### Nothing appears in simple plot

I'm trying to get the following simple code to work. (The code is just supposed to graph the norm of the second derivative of a vector function). ...
684 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 ...
135 views

### Why does evaluating an integral within a Plot expression take so long? [duplicate]

I want to evaluate Plot[Integrate[Sin[((1 + 1/2) x)] (1/(2 Sin[(x/2)]) - 1/x), {x, 0, t}], {t, 0, 5}] but it takes ages to load on Corei3 computer with ...
250 views

### Half-delayed evaluation

In a certain wider context, I need to make some delayed definitions, such as x := a + b + c, but within these definitions I want ...
40 views

### Notification when evaluation completes [duplicate]

I thought it would be fun to see a list of ways to have Mathematica notify you when a long evaluation completes. There are a few posts up already that address specific methods, given below, but not ...
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### RandomReal behavior in Block environment [duplicate]

I ran into an unexpected behavior of RandomReal function inside the Block environment. If I simplify my problem: I wanted to use two random local variables, such that the second one would be less that ...
593 views

### How to tell Mathematica not to simplify an expression

While there is this question with a very similar title, it does not answer my question, which is: I have part of an input, in my case Re[Exp[I*x]] which ...
100 views

### How to modify the file “KeyEventTranslations.tr” to use Enter to evaluate the current cell? [duplicate]

I asked the following question before, but I do not think it has been fully answered. By default, we use Shift+Enter to evaluate the current cell, and use Enter to get a new line. Is there a way ...
2k views

### How to evaluate Modules in a notebook from another notebook?

I would like to create a notebook populated with several modules and be able to evaluate these modules by running a separate notebook. I have attempted several uses of the ...
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### Number precision in a list [duplicate]

I have list with elements: ...
104 views

### Evaluate integral of a series

I want to evaluate this integral, but it won't work. Does anyone knows why? ...
84 views

### Can I have Mathematica show intermediate forms before final evaluation?

If I have x = 2 and I want to evaluate y = x^2 I would like to the output to show ...
84 views

### Extract the real components from a very large expression

Suppose I have a very long expression (>500,000 characters) which contains a mixture of real and imaginary terms. e.g ...
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### is there a way to construct a pattern that would trigger when an expression is used as a held/unevaluated in some form?

For example, consider the following code f[x_] := (Print["evaluated f"]; workWith[x]); We use it, then f evaluates: ...
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### 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 ...
250 views

### Nested Derivative

These two expressions are mathematically the same, but when substituting with the same rule, yield different results. What is happening? ...
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: ...
129 views

### Merging two held expressions into a held compound expression

Consider e1 = Hold[a = x + x; b = y + y + y]; e2 = Hold[c = a + a + b + b + b; c^2]; How can I obtain the following? ...
289 views

### Why does Plot[Hold[x], {x,0,1}] work?

It appears that, counter to my expectation, all of these (and probably many others) seem to work fine: ...
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### Assign a value to a variable without using Set or SetDelayed?

I supose probably yes, but at the end I assume that internally mathematica has to use Set or SetDelayed. Am I right? Background: I am developing a super simple phraser that takes a code description ...
83 views

### Commutative algebra by generators and quadratic relations

My apologies if this has been asked before. Please also be gentle, as this is my first question here. I am trying to define a commutative algebra by generators and relations in the following way. ...