[Rcpp-devel] Parameter Naming (was: Speed gain assistance)

[Dirk Eddelbuettel]

On 18 August 2011 at 16:24, Darren Cook wrote:
| I'd like to shamelessly hijack Christopher Wray's question to ask if
| there is a convention for parameter naming with Rcpp and inline. Well,
| actually I'll propose one, to then see what others prefer.
| 
| First I would propose to use long variable names, instead of
| abbreviations, in both the CPP and R sides [1]. I already know enough R
| to know this will be immediately rejected ;-) [2]
| 
| Anyway, while trying to understand the posted code I found myself
| jumping back and forth between the below two blocks of code, muttering
| to myself, "so the bottleneck is proportional to 2nd parameter which is
| SamSize, which is then called SS_C, ..."
| 
| > src<-'
| > NumericVector RetIn(RetVec);
| > int SS_C=as<int>(SamSize); 
| > double St_C=as<double>(StM);
| > int ES_C=as<int>(ExpSize);
| > ...
| > sscpp2<-cfunction(
| > signature(RetVec="numericVector",SamSize="numeric",StM="numeric",ExpSize="numeric"),
| > src,inc, Rcpp=TRUE,cppargs="",convention=".Call")
| 
| So, my proposal would be to use the same names in the signature that you
| intend to use in the C++ code, but with underline appended. I.e.

You must do that anyway or you get linking errors.

The rest is stylistic, and we do not impose a style (besides maybe the
default indentation I get from Emacs :). If you need a style, I suggest to
follow R conventions as layed out in the R Internals manual. Personally, I
also like this one:

   http://quantlib.org/style.shtml

Descriptive names are good, comments are good, using separate names for
members vars is good and I still mostly prepend m_. 

Dirk


| signature(RetIn_="numericVector",SS_C_="numeric",St_C_="numeric",ES_C_="numeric")
| 
| The C++ code then starts:
|   NumericVector RetIn(RetIn_);
|   int SS_C=as<int>(SS_C_);
|   double St_C=as<double>(St_C_);
|   int ES_C=as<int>(ES_C);
| 
| What conventions are other people using?
| 
| Darren
| 
| [1]: I am not alone in this. E.g. see "Rename Method" in Martin Fowler's
| Refactoring; "It's All Writing" in The Pragmatic Programmer (ch.8); etc.
| 
| [2]: I realize many R functions are direct translations of mathematical
| functions, so calling a parameter "p" is not as meaningless as it
| appears at first glance. I still think it should be "probabilities" not
| "p" (yes, "qunif", I'm looking at you), but I realize I'm in a minority
| when surrounded byq mathematicians.
| 
| 
| 
| 
| -- 
| Darren Cook, Software Researcher/Developer
| 
| http://dcook.org/work/ (About me and my work)
| http://dcook.org/blogs.html (My blogs and articles)
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