# 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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### “And” to continue evaluation after “False”

Below, is it possible to print No and have x be 2. That is, I'm looking for an And-like function that looks at all arguments ...
243 views

### Associativity of /@ [duplicate]

Why are the following not equivalent: Map[Line, Map[(Print[#]; #) &, {{{2, 1}, {1, 1}}, {{-2, 1}, {3, 1}}}]] which produces ...
283 views

### difficulty abstracting the OptionValue pattern

I am building lots of functions that use Options and OptionValue and wanted to reduce the redundancy in the expressions that ...
152 views

### Evaluate numerically an extremely small number

How to evaluate numerically $e^{-4 \cdotp 10^{35}}$ in the form $0,a_1a_2...\times 10^{-n}$ ...
318 views

### Evaluate notebook from other notebook

I have a notebook ("notebook 1") which in the beginning sets some parameters, does something depending on their value and saves the result to a file, say: ...
830 views

### How to make a function that evaluates an expression?

I'm trying to make a function where the input is an expression, but somehow it just won't be evaluated. For example, this little function doesn't work: ...
465 views

### Strange Error in Bifurcation Diagram:

I am attempting to plot the bifurcation diagram of the tent map $$f(x):=2\alpha \begin{cases} x, & 0<x<1/2\\ 1-x, &1/2<x<1, \end{cases}$$ i.e., the plot $\alpha$ vs. the limit ...
240 views

### Parts of Module body evaluated in external scope?

I have an expression that suggests that some expressions in a module body are dragging in definitions from outside the scope in a surprising way. First, consider a symbolic constant, ...
125 views

### Why does Rule behave like this?

Why does {x, x^2, x^3, a, b} /. x^n_ -> f[n] result in {x, f[2], f[3], a, b} when ...
277 views

### Why doesn't Evaluate appear to work in this RegionPlot example with MatchQ?

I am trying to plot the region over which a function of two (real) parameters a and b is real-valued, using ...
894 views

### Expression evaluation inside of FindRoot inside a Compiled Function

I'm trying to get some performance increase out of my own implicit differential equation solver using Compile[]. The uncompiled function is of the following form: ...
688 views

### Delayed evaluation of assignment

I have a set of PDE's that depend on parameters. They depend on many parameters, but for simplicity we can here assume that they depend only on one, say a. I want ...
1k views

### How can I save the current evaluation state of a notebook and start from it later?

I currently have a nested Table command running (in Mathematica 9), with two progress bars to track the variables. I have to shut down or hibernate the computer in ...
986 views

### Prevent Mathematica to automatically evaluate Manipulate at start

I'm using an initialization cell to import a lot of data: data = Import[myFiles]; and then I use a custom function to display this data with Manipulate: ...
393 views

### Manipulate Evaluation Order Problem

I seem to be getting some unintended results from a nested Manipulate that I have not been able to resolve. I boiled down the problem I'm having to a simplified ...
194 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 ...
108 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 ...
134 views

### A pre-parsed HoldForm

HoldForm holds an expression's parsed form not its actual "inputted form" e.g. ...
192 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" ...
257 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 ...
227 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 ...
89 views

### How can a function without an operator form be used in postfix form?

As an exercise, I was trying to convert the following Clojure code to Mathematica: ...
49 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 ...
55 views

### How to evaluate following inputs only after finishing CreateDialog

I have a code which starts with the following Cell: ...
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 ...
35 views

306 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: ...