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
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How do you use "<<-" (scoping assignment) in R?
I just finished reading about scoping in the R intro, and am very curious about the <<- assignment.
The manual showed one (very interesting) example for <<-, which I feel I understood. What I am still missing is the context of when this can be…
Tal Galili
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103
votes
18 answers
Javascript function scoping and hoisting
I just read a great article about JavaScript Scoping and Hoisting by Ben Cherry in which he gives the following example:
var a = 1;
function b() {
a = 10;
return;
function a() {}
}
b();
alert(a);
Using the code above, the browser…
dev.e.loper
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votes
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Node-style require for in-browser javascript?
Are there any libraries for in-browser javascript that provide the same flexibility/modularity/ease of use as Node's require?
To provide more detail: the reason require is so good is that it:
Allows code to be dynamically loaded from other…
Alex Churchill
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votes
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What is the difference between my and local in Perl?
I am seeing both of them used in this script I am trying to debug and the literature is just not clear. Can someone demystify this for me?
Brian G
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58
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Is it a good practice to call functions in a package via ::
I'm writing some R functions that employ some useful functions in other packages like stringr and base64enc. Is it good not to call library(...) or require(...) to load these packages first but to use :: to directly refer to the function I need,…
Kun Ren
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44
votes
3 answers
"except Foo as bar" causes "bar" to be removed from scope
Given the following code:
msg = "test"
try:
"a"[1]
except IndexError as msg:
print("Error happened")
print(msg)
Can somebody explain why this causes the following output in Python 3?
Error happened
Traceback (most recent call last):
File…
knipknap
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What are the double colons (::) in R?
I am following a tutorial in Rbloggers and found the use of double colons, I looked online, but I couldn't find an explanation for their use.
Here is an example of their use.
df <- dplyr::data_frame(
year = c(2015, NA, NA, NA),
trt = c("A",…
Luis Candanedo
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votes
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Are variables statically or dynamically "scoped" in javascript?
Or more specific to what I need:
If I call a function from within another function, is it going to pull the variable from within the calling function, or from the level above? Ex:
myVar=0;
function runMe(){
myVar = 10;
callMe();
}
function…
kylex
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Python class scoping rules
EDIT: Looks like this is a very old "bug" or, actually, feature. See, e.g., this mail
I am trying to understand the Python scoping rules. More precisely, I thought that I understand them but then I found this code here:
x = "xtop"
y = "ytop"
def…
ivanl
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30
votes
3 answers
Dynamic Scoping - Deep Binding vs Shallow Binding
I've been trying to get my head around shallow binding and deep binding, wikipedia doesn't do a good job of explaining it properly. Say I have the following code, what would the output be if the language uses dynamic scoping with
a) deep binding
b)…
John Jiang
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30
votes
1 answer
How can a non-imported method in a not-attached package be found by calls to functions not having it in their namespace?
An R namespace acts as the immediate environment for all functions in its associated package. In other words, when function bar() from package foo calls another function, the R evaluator first searches for the other function in
Josh O'Brien
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Why use a do-end block in Lua?
I keep trying to find answers for this but fail to do so. I wanted to know, what is the do-end block actually used for? It just says values are used when needed in my book so how could I use this?
Do I use it to reduce the scope of local variables…
Mayron
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attach() inside function
I'd like to give a params argument to a function and then attach it so that I can use a instead of params$a everytime I refer to the list element a.
run.simulation<-function(model,params){
attach(params)
#
# Use elements of params as parameters in a…
statistician_in_training
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21
votes
3 answers
could not find function inside foreach loop
I'm trying to use foreach to do multicore computing in R.
A <-function(....) {
foreach(i=1:10) %dopar% {
B()
}
}
then I call function A in the console. The problem is I'm calling a function Posdef inside B that is defined in another…
statistician_in_training
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