Questions on Mathematica's scoping constructs (Block, Module, With, etc.)

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9
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2answers
207 views

How to define UpValues in a different context from within a package

I'm trying to create a function (in a package) to import a lot of data and create a symbol with UpValues to return specific results about the data. I've got it working fine in a regular notebook, but ...
0
votes
0answers
68 views

What's the best practice for nested local constants? [duplicate]

Possible Duplicate: How to avoid nested With[]? I have many situations where I have a constant that is local to a function, with other constants that are computed from it. I see that I can ...
10
votes
2answers
368 views

Localizing variables within a Manipulate

I have a notebook with several examples of very similar computations, each involving the same variable/parameter names of the ingredients used in a final Manipulate....
15
votes
1answer
366 views

Modules that initialize themselves on first call

I use a lot of functions that extract a specific data item from a file with many data items. I want these functions to load data (slow) and return the item (fast) on first call, but just return the ...
24
votes
2answers
1k views

What are some advanced uses for Block?

I read the answers to this question (What are the use cases for different scoping constructs?) and this one (Condition, Block, Module - which way is the most memory and computationally efficient?). ...
4
votes
2answers
316 views

Comparing LetL and Module efficiency

I was recently introduced to the LetL macro thanks to Leonid's answer to one of my prior questions. I was, needless to say, impressed by the simplicity of its ...
58
votes
6answers
2k views

How to avoid nested With[]?

With[ {v1 = #}, With[ {v2 = f[v1]}, g[v1, v2] ] ] How to avoid nested With[] like the above? I'd like to use <...
0
votes
1answer
143 views
22
votes
3answers
486 views

Nested definition: How can I define a function with a passed-in expression?

Here's a simplified version of what I'm trying to do: ...
10
votes
2answers
302 views

Strange results while nesting scope constructs?

I did a handful of tests with Block, With, and Module and had a couple of new surprises. ...
5
votes
1answer
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, ...
1
vote
1answer
243 views

Using block or module to free cache

I'm writing some code at the moment that schematically looks like: (set initial conditions for some differential equation for given parameters (M,R,...)) ...
39
votes
1answer
1k views

Local variables in Module leak into the Global context

From the Mathematica documentation on Module: Module allows you to set up local variables with names that are local to the module. But after using ...
39
votes
3answers
1k views

Why modules with no variables?

I was reading some code, in particular, recipe 4.13 on unification pattern-matching in Sal Mangano's Mathematica Cookbook, and there were many instances of Modules with no variables in them, such as ...
10
votes
2answers
356 views

Avoiding MainEvaluate in a CompiledFunction to fetch global variables

I'm trying to write a simulation using Mathematica 8.0. Since I will most likely be doing the same operation over and over again, I'm trying to Compile whatever I ...
11
votes
2answers
1k views

Scoping in assigning a derivative

While answering another question, I stumbled upon a problem I cannot easily resolve. To assign the derivative of a function to another function, typically one can do this with a ...
3
votes
2answers
109 views

Is there a way to localize Off[some::message]?

Is there a way to temporarily suppress certain messages, so that I could write for example (with made-up syntax for that feature): ...
2
votes
2answers
796 views

Scoping inside of Module and Manipulate

This is driving me nuts: I'm trying to control the parameters for a relatively large system of ODEs using Manipulate. ...
4
votes
1answer
267 views

How to avoid conflicts between local variable names and symbolic arguments in Block constructs?

I am using Block inside the definition of some recursive functions. If the Block definitions use short variable names, like ...
8
votes
2answers
144 views

Question about scoping data in a multi-level Manipulate construction

Background: In a module containing an outer / inner manipulate I select the key of data with a dropdownlist in the outer manipulate. Data is read and displayed in the inner manipulate for edit ...
9
votes
3answers
1k views

How to use local variables with indices in a Mathematica Block environment?

I have the following code: Subscript[f, i_][x_] := Block[{a}, Subscript[a, i] = 3 x; Subscript[a, 1] ] If I evaluate for example ...
8
votes
1answer
223 views

Difficulty catching thrown errors in asynchronous tasks

In this Question, Leonid explained that module variables can get garbage collected from a chain of asynchronous tasks unless their Temporary attribute is cleared ...
7
votes
1answer
281 views

Module variable scoping in Scheduled Tasks?

I ran across a scoping puzzle while experimenting with ScheduledTasks, and I'd be grateful for an explanation from the sages here. I found a workaround by intuitive horse sense, but was unable to ...
10
votes
3answers
366 views

Find variable name from DumpSave on a scoped variable

I saved an InterpolationFunction in a ".mx" files using DumpSave on a variable that was scoped by a ...
5
votes
3answers
295 views

Notation for specifying transformation rules

I would like to have a compact notation for specifying conditions and results in transformation rules. Consider ReplaceAll: ...
4
votes
2answers
655 views

Local variables

I'm trying to use Modules together with functions. tmp2 = x^2 + 1; f[y_] := Module[{x = 1}, Evaluate[y tmp2]] This works when ...
8
votes
3answers
175 views

With/Function(/etc) replacement behaviour

Can anyone explain to me this behaviour? I've been having more than a couple of similar doubts these last weeks. For example f[_?NumericQ] := 8; Now, if I do <...
11
votes
4answers
911 views

Subscripts - Why do I see the error “only assignments to symbols are allowed” when using a Module and not otherwise?

When I type Remove["Global`*"] foo[] := Module[{Subscript[a, 1] = "x"}, 0]; foo[] I get the expected error "only assignments to symbols are allowed". I ...
7
votes
6answers
636 views

How can you give a Module a context and have its local variables and Modules belong to that context?

What would be the best way to give a module its own context and have its local variables and Modules belong to that context?
149
votes
7answers
7k views

What are the use cases for different scoping constructs?

Mathematica includes three functions that I know of which can be used to effectively (if not actually) define a variable and give it a value within a local scope: ...