# 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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### What happens when you divide by ##?

I've been playing around with sequences a bit. In particular with using ## with unary and binary operators. Let's start simple, the following all make some kind of ...
2k views

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### Make a button that evaluates a function over and over

I would like to have a command "RedoButton" which would make a button (or whatever control is suitable) that when clicked would print the value of a certain function over and over in the same place. ...
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### Bags and non-standard evaluation

What can internally be happening here? Is the evaluator just messing with us and going non-standard because it's a Bag? Or am I just not seeing how something like ...
242 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 ...
424 views

### When must I use the Return function?

In a comment to my answer to this question, QuantumDot asks, "Where can I find more information on when I must use the 'Return' function?". I found this too deep a question to be answered by leaving a ...
423 views

### How can I hold UpValues but evaluate other expressions?

Consider these definitions: own = "OwnValue"; down[_] = "DownValue"; sub[_][_] = "SubValue"; N[n] = 3.14; _[___, up, ___] ^= "UpValue"; The attribute ...
550 views

### Get the name of a symbol passed to a function

I'm trying to get the name of a symbol passed to a function with this: f[x_] := {SymbolName[x], x} SetAttributes[f, HoldFirst] x = 5; f[x] But ...
791 views

### DSolve cannot solve for certain branches of the solution

Update - This has been fixed in 10.0.0 Could somebody please tell me, why I am always getting an error message when trying to run the following code: ...
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### Old values are not freed/garbage collected when you re-evaluate an assignment

For this code: (* Cell 1 *) generate := Module[{x}, x = Range[100 * 1000 * 1000]; x]; (* Cell 2 *) g = generate[]; MemoryInUse[] If I evaluate cell 2 repeatedly,...
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### 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 ...
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### Labeling plots without evaluation

This is my first question here so please excuse my mistakes. Let us consider a rather contrived example: ...
290 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: ...