Questions tagged [free-variable]
31 questions
37
votes
4 answers
What are free variables?
Javascript closure definition says :
A "closure" is an expression (typically a function) that can have free
variables together with an environment that binds those variables
(that "closes" the expression).
Can some one explain to me the…
Geek
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23
votes
2 answers
What are Free and Bound variables?
I've been programming for a long time (too long, actually), but I'm really struggling to get a handle on the terms "Free Variables" and "Bound Variables".
Most of the "explanations" I've found online start by talking about topics like Lambda…
Roddy
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15
votes
3 answers
Can a pure function have free variables?
For example, a referentially transparent function with no free variables:
g op x y = x `op` y
A now now a function with the free (from the point-of-view of f) variables op and x:
x = 1
op = (+)
f y = x `op` y
f is also referentially transparent. …
Matt Fenwick
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9
votes
3 answers
How can "NameError: free variable 'var' referenced before assignment in enclosing scope" occur in real code?
While I was hanging out in the Python chatroom, someone dropped in and reported the following exception:
NameError: free variable 'var' referenced before assignment in enclosing scope
I'd never seen that error message before, and the user provided…
Zero Piraeus
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6
votes
1 answer
Free variables list of a lambda expression
I was just doing some homework for my upcoming OCaml test and I got into some trouble whatnot.
Consider the language of λ-terms defined by the following abstract syntax (where x is a variable):
t ::= x | t t | λx. t
Write a type term to…
rickmeizter
- 131
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- 7
5
votes
4 answers
Free Variable in Prolog
Can anyone explain the concept of free variables in Prolog. Is it similar to anonymous variables ? Or is there a difference. Also could be great if an example is given to explain.
Devansh Shah
- 55
- 4
3
votes
2 answers
Which Vars affect a Clojure function?
How do I programmatically figure out which Vars may affect the results of a function defined in Clojure?
Consider this definition of a Clojure function:
(def ^:dynamic *increment* 3)
(defn f [x]
(+ x *increment*))
This is a function of x, but…
Jouni K. Seppänen
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3
votes
1 answer
Destroy type in Julia
I have to destroy some type in Julia which looks like:
struct City
x::Int
y::Int
index::Int
end
and I want a function like
destroy(City)
that will delete this. Is it possible?
Thanks for your answers.
blue rabbit
- 139
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3
votes
2 answers
Return a list of free(unbound) variables in SML
I've created my own datatypes:
datatype typ = Bool | Int | Arrow of typ*typ;
(* i.e., Arrow(argType, returnType) *)
(* diMLazy expressions *)
datatype expr = TrueExpr
| FalseExpr
| IntExpr of int
| VarExpr…
NickBolden
- 31
- 2
3
votes
1 answer
`del` statement and free variables
Testing some Python code today I tried the following code:
(The following runs on Python 3.2+, although previous versions will raise a SyntaxError when del is used and a variable is referenced in an enclosing scope)
def x():
N = 200
def…
GIZ
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2
votes
1 answer
Are variables bounded to free variables still free variables?
I am looking at some questions in my textbook about whether or not the variables are free or bound. I am not sure about these two in particular.
First off, I want to make sure I understand the concept of free vs. bound. I am fairly sure this x is a…
bobaloogie
- 45
- 5
2
votes
1 answer
How do I solve this constrained linear programing (LP) problem with one free variable?
I was researching methods to rank forecasts and found this paper, A novel ranking procedure for forecasting approaches using Data Envelopment Analysis, I've been working through the article and setting up my data, but I can't seem to replicate their…
KrutonCrab
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- 6
2
votes
2 answers
Will recursively-called variable be free or bound?
I am trying to have a better understanding about free and bound variables. Here is an example code:
(define (what-kind-of-var? guess x)
(< (abs (- (square guess) x))
0.001))
I see that bound variables here would be guess and x, and free…
Isaac
- 273
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2
votes
2 answers
Finding list/map of free variable(s) of a closure in groovy
This is my simple groovy script;
def fourtify(String str) {
def clsr = {
str*4
}
return clsr
}
def c = fourtify("aa")
println("binding variables: ${c.getBinding().getVariables()}")
...
All I'm trying to do here is being able…
stdout
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2
votes
1 answer
Free variables treated as globals in Python?
In the Execution Model section of the Python 3.7 reference manual I read the following statement:
The global statement has the same scope as a name binding operation in the same block. If the nearest enclosing scope for a free variable contains a…
saveturn
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