R help - May 2012 - `mapply(function(x) function() x, c("a", "b"))$a()' returns `"b"'

As the title says, I want to apply a function (which itself returns
a function) to a list (or vector), and get a list (or vector) of
generated functions as the return value, but get unexpected result.

Anyone with an idea about the reason of this phenomenon and a correct
way to implement the requirements? Thanks very much :)

-- 
Using GPG/PGP? Please get my current public key (ID: 0xAEF6A134, valid
from 2010 to 2013) from a key server.

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As i see it you will save the actual "text" of the function - and when
you call it later on it takes the last value of x it has encountered as the
value. I guess you want the x not to be saved as x, but as "a" or
"b", so, as its value.

I am not sure how to do that however as of yet.


Am 03.05.2012 um 12:31 schrieb Casper Ti. Vector:
> As the title says, I want to apply a function (which itself returns
> a function) to a list (or vector), and get a list (or vector) of
> generated functions as the return value, but get unexpected result.
> 
> Anyone with an idea about the reason of this phenomenon and a correct
> way to implement the requirements? Thanks very much :)
> 
> -- 
> Using GPG/PGP? Please get my current public key (ID: 0xAEF6A134, valid
> from 2010 to 2013) from a key server.
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

Now.. i just tried around and this might be a bit strange way to do things..

createFunc<-function(v){
	v_out<-NULL
	for(i in v){
		v_out[[i]]<-substitute(function(){x},list(x=i))
	}
	return(v_out)
}
> y<-createFunc(c("a","b"))
> y
$a
function() {
    "a"
}

$b
function() {
    "b"
}
> eval(y$a)()
[1] "a"
> eval(y$b)()
[1] "b"

Am 03.05.2012 um 12:31 schrieb Casper Ti. Vector:
> As the title says, I want to apply a function (which itself returns
> a function) to a list (or vector), and get a list (or vector) of
> generated functions as the return value, but get unexpected result.
> 
> Anyone with an idea about the reason of this phenomenon and a correct
> way to implement the requirements? Thanks very much :)
> 
> -- 
> Using GPG/PGP? Please get my current public key (ID: 0xAEF6A134, valid
> from 2010 to 2013) from a key server.
> 
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

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