Scoping associates a name with an entity. For an object to be *in scope* means that it is possible to write a snippet of code referencing value and location of that object by its name. Lexical scoping refers to a proportion of text whereas dynamic scoping corresponds to the proportion of run time.
Questions tagged [scoping]
584 questions
17
votes
5 answers
Variables as default arguments of a function, using dplyr
Goal
My goal is to define some functions for use within dplyr verbs, that use pre-defined variables. This is because I have some of these functions that take a bunch of arguments, of which many always are the same variable names.
My understanding:…
Axeman
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16
votes
4 answers
Scope functions apply/with/run/also/let: Where do their names come from?
There are quite a few blog posts (like this) on usages of the standard library functions apply/with/run/also/let available that make it a bit easier to distingish when to actually use which of those pretty functions.
For a few weeks now, the…
s1m0nw1
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16
votes
3 answers
Can I "extend" a closure-defined "class" in Javascript?
I have a Javascript "class" defined like so:
var Welcomer = function(name) {
var pName = name;
var pMessage = function() {
return "Hi, " + pName + "!";
};
return {
sayHi: function() {
alert(pMessage());
}
};
};
new…
James A. Rosen
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16
votes
1 answer
Static Variables Initialization Quiz
#include
class C
{
public:
static int i;
static int j;
};
int i = 10;
int C::i = 20;
int C::j = i + 1;
int main ()
{
printf("%d", C::j);
return 0;
}
What is the value of: C::j
I was reading a c++ quiz…
marsh
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16
votes
3 answers
Set a functions environment to that of the calling environment (parent.frame) from within function
I am still struggling with R scoping and environments. I would like to be able to construct simple helper functions that get called from my 'main' functions that can directly reference all the variables within those main functions - but I don't…
Charlie
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16
votes
2 answers
Passing variables to $.ajax().done()
I'm lost. How might I pass a loop variable to an AJAX .done() call?
for (var i in obj) {
$.ajax(/script/).done(function(data){ console.log(data); });
}
Obviously, if I were to do console.log(i+' '+data) i would return the very last key in the…
Phil Tune
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15
votes
5 answers
Why does using the same count variable name in nested FOR loops work?
Why does the following not give an error?
for (int i=0; i<10; ++i) // outer loop
{
for (int i=0; i<10;++i) // inner loop
{
//...do something
}
//...do something else
}
The way I understand it, variables in braces ({...}) are in…
M Perry
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14
votes
1 answer
Common Lisp scoping (dynamic vs lexical)
EDIT: I changed the example code after the first answer because I came up with a simple version that begs the same questions.
I am currently learning Common Lisp's scoping properties. After I thought I had a solid understanding I decided to code up…
Anthony Naddeo
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14
votes
4 answers
Scoping and functions in R 2.11.1 : What's going wrong?
This question comes from a range of other questions that all deal with essentially the same problem. For some strange reason, using a function within another function sometimes fails in the sense that variables defined within the local environment…
Joris Meys
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14
votes
8 answers
What methods are there to modularize C code?
What methods, practices and conventions do you know of to modularize C code as a project grows in size?
Ari Ronen
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13
votes
1 answer
Any way to access function installed by makeActiveBinding?
The title basically says it all.
If I do this ...
makeActiveBinding("x", function() runif(2), .GlobalEnv)
x
# [1] 0.7332872 0.4707796
x
# [1] 0.5500310 0.5013099
... is there then any way for me to examine x to learn what function it is linked to…
Josh O'Brien
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12
votes
2 answers
When should i be opening and closing MongoDB connections?
i am very new to MongoDB and NoSQL in general and i've just started building a site with MongoDB / Norm / ASP.NET MVC 3.
I am wondering how i should be scoping the connections to my Mongo database.
Right now i have a Basecontroller that instanciates…
Kimpo
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12
votes
0 answers
Why does this python code exhibit weird scoping rules
I'm running on Python 2.7.8 (Anaconda Distribution) and this code fails. This looks like a bug in the Python implementation, but am I missing anything?
class C:
x = {2 : 1}
y = {w for w in x if x[w]==1}
Running this code gives the following…
greg
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12
votes
1 answer
Python scoping in dict comprehension
>>> x = 'foo'
>>> {0: locals().get('x')}
{0: 'foo'}
>>> {0: locals().get('x' + spam) for spam in ['']}
{0: None}
What is the reason for this discrepancy in behaviour?
wim
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11
votes
3 answers
curve3d can't find local function "fn"
I'm trying to use the curve3d function in the emdbook-package to create a contour plot of a function defined locally inside another function as shown in the following minimal example:
library(emdbook)
testcurve3d <- function(a) {
fn <-…
Jarle Tufto
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