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1

I am using a function factory defined by someone else and I cannot change it. It is common to need to generate several functions with this factory at the beginning of every run. In my attempt at a toy example, it's as if I need many such power_ functions frequently. Currently as a user of otherpackage, I must include lines like power2 <- power_factory(2) in my scripts.

otherpackage::power_factory <- function(exp) 
 function(x) 
 x ^ exp
 


power2 <- power_factory(2)
power3 <- power_factory(3)

I would like to avoid these lines by writing my own package, so I can instead use mypackage::power2() in my scripts. Normally, if I wanted to wrap these functions in a package, I could just use the factory to build them inside the package. However, this factory depends on some outside input, here credential, that I cannot write inside my package. This makes the factory error if I put power2 <- power_factory(2) inside the package:

# credential <- "my_secret"
otherpackage::power_factory <- function(exp) 
 print(credential)
 function(x) 
 x ^ exp
 


power2 <- power_factory(2)
#> Error in print(credential): object 'credential' not found

^{Created on 2019-03-07 by the reprex package (v0.2.1)}

Is there a way around this problem? The end goal, as above, is to be able to call mypackage::power2() instead of needing to do power2 <- power_factory(2) and many variations on such at the start of each script.

r

share|improve this question

edited Mar 8 at 0:43

Calum You

asked Mar 8 at 0:01

Calum YouCalum You

8,0721930

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  When you load mypackage, the namespace is typically locked once loaded, so the user later wanting to define power2 does not necessarily work. There are cheats around this, but I have yet to hear somebody recommend solid rationale why this should be allowed and easy. Is there a reason you cannot make it an argument of the factory, as in power_factory(2, credential)?
  
  – r2evans
  Mar 8 at 0:38
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  The reason is that I cannot edit power_factory since it comes from a different, non-public package (and I can't speak to the reasons for the author choosing to make the interface like this). I am not sure what you mean by the "user later wanting to define power2", I'll add some clarifying text
  
  – Calum You
  Mar 8 at 0:41
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  Where and when is credential defined? You can write your own function factory as a wrapper around the other factory, thereby safe-guarding acquisition of the credential, such as myfactory <- function(...) credential <- get_credential(); otherpackage::power_factor(...);
  
  – r2evans
  Mar 8 at 2:25
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  You can achieve this by creating an environment env with the credential and then setting the power_factor function environment to env. See the McFlick's answer here: stackoverflow.com/questions/12279076/…. In particular the helper function with_env
  
  – dipetkov
  Mar 8 at 2:56
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I was able to get the wrapper working r2evans, will accept if you submit as answer
  
  – Calum You
  Mar 14 at 20:57
  

  
  
  
  

add a comment | 

1

I am using a function factory defined by someone else and I cannot change it. It is common to need to generate several functions with this factory at the beginning of every run. In my attempt at a toy example, it's as if I need many such power_ functions frequently. Currently as a user of otherpackage, I must include lines like power2 <- power_factory(2) in my scripts.

otherpackage::power_factory <- function(exp) 
 function(x) 
 x ^ exp
 


power2 <- power_factory(2)
power3 <- power_factory(3)

I would like to avoid these lines by writing my own package, so I can instead use mypackage::power2() in my scripts. Normally, if I wanted to wrap these functions in a package, I could just use the factory to build them inside the package. However, this factory depends on some outside input, here credential, that I cannot write inside my package. This makes the factory error if I put power2 <- power_factory(2) inside the package:

# credential <- "my_secret"
otherpackage::power_factory <- function(exp) 
 print(credential)
 function(x) 
 x ^ exp
 


power2 <- power_factory(2)
#> Error in print(credential): object 'credential' not found

^{Created on 2019-03-07 by the reprex package (v0.2.1)}

Is there a way around this problem? The end goal, as above, is to be able to call mypackage::power2() instead of needing to do power2 <- power_factory(2) and many variations on such at the start of each script.

r

share|improve this question

edited Mar 8 at 0:43

Calum You

asked Mar 8 at 0:01

Calum YouCalum You

8,0721930

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  When you load mypackage, the namespace is typically locked once loaded, so the user later wanting to define power2 does not necessarily work. There are cheats around this, but I have yet to hear somebody recommend solid rationale why this should be allowed and easy. Is there a reason you cannot make it an argument of the factory, as in power_factory(2, credential)?
  
  – r2evans
  Mar 8 at 0:38
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  The reason is that I cannot edit power_factory since it comes from a different, non-public package (and I can't speak to the reasons for the author choosing to make the interface like this). I am not sure what you mean by the "user later wanting to define power2", I'll add some clarifying text
  
  – Calum You
  Mar 8 at 0:41
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  Where and when is credential defined? You can write your own function factory as a wrapper around the other factory, thereby safe-guarding acquisition of the credential, such as myfactory <- function(...) credential <- get_credential(); otherpackage::power_factor(...);
  
  – r2evans
  Mar 8 at 2:25
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  You can achieve this by creating an environment env with the credential and then setting the power_factor function environment to env. See the McFlick's answer here: stackoverflow.com/questions/12279076/…. In particular the helper function with_env
  
  – dipetkov
  Mar 8 at 2:56
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  I was able to get the wrapper working r2evans, will accept if you submit as answer
  
  – Calum You
  Mar 14 at 20:57
  

  
  
  
  

add a comment | 

I am using a function factory defined by someone else and I cannot change it. It is common to need to generate several functions with this factory at the beginning of every run. In my attempt at a toy example, it's as if I need many such power_ functions frequently. Currently as a user of otherpackage, I must include lines like power2 <- power_factory(2) in my scripts.

otherpackage::power_factory <- function(exp) 
 function(x) 
 x ^ exp
 


power2 <- power_factory(2)
power3 <- power_factory(3)

I would like to avoid these lines by writing my own package, so I can instead use mypackage::power2() in my scripts. Normally, if I wanted to wrap these functions in a package, I could just use the factory to build them inside the package. However, this factory depends on some outside input, here credential, that I cannot write inside my package. This makes the factory error if I put power2 <- power_factory(2) inside the package:

# credential <- "my_secret"
otherpackage::power_factory <- function(exp) 
 print(credential)
 function(x) 
 x ^ exp
 


power2 <- power_factory(2)
#> Error in print(credential): object 'credential' not found

^{Created on 2019-03-07 by the reprex package (v0.2.1)}

Is there a way around this problem? The end goal, as above, is to be able to call mypackage::power2() instead of needing to do power2 <- power_factory(2) and many variations on such at the start of each script.

r

share|improve this question

edited Mar 8 at 0:43

Calum You

asked Mar 8 at 0:01

Calum YouCalum You

8,0721930

otherpackage::power_factory <- function(exp) 
 function(x) 
 x ^ exp
 


power2 <- power_factory(2)
power3 <- power_factory(3)

# credential <- "my_secret"
otherpackage::power_factory <- function(exp) 
 print(credential)
 function(x) 
 x ^ exp
 


power2 <- power_factory(2)
#> Error in print(credential): object 'credential' not found

share|improve this question

edited Mar 8 at 0:43

Calum You

asked Mar 8 at 0:01

Calum YouCalum You

8,0721930

share|improve this question

edited Mar 8 at 0:43

Calum You

asked Mar 8 at 0:01

Calum YouCalum You

8,0721930

asked Mar 8 at 0:01

Calum YouCalum You

8,0721930

asked Mar 8 at 0:01

Calum YouCalum You

8,0721930