On Wed, 4 Apr 2007, Peter Ruckdeschel wrote: > Hi R-devels, > > I would like to ask for your advice on the preferred way to exchange > information between functions aside from the regular argument/return-value > interface. > > I am well aware that, S being a functional language, this is to be avoided > where possible. There are exceptions, though: > > Let myF() and myH() be functions provided by me, and notmyG() be a function > provided by someone else. > > The calling hierarchie is myF() calls notmyG() which calls --- possibly > with other functions being called in between --- myH(). > > notmyG() takes as argument a function with return value of type numeric > --- typically a function for optimizing, integrating or zero-finding --- > and is a function which I do not want to modify (and subsequently maintain > the modification). > > As myH() is expensive as to evaluation time and, as a side effect, also > provides important side information, I would like to pass this information > back to myF(). (Also see example below). > > Using information from myF() in myH() by lexical scoping is straight > forward, whereas to pass information from myH() to myF() directly, the > solution I found so far is to use assign() with a corresponding > envir=./pos=.-argument. > > (Q1) Is there a better way to do so? >
Sounds like lexical scoping should work for this also -- use <<- to assign to the variable in the containing scope. Best, luke > While it is not too difficult to find out the correct value for the > envir/pos argument when using "pure" R-functions for notmyG(), the > situation is a little more complicated as soon as notmyG() calls myH() > through intermediate calls to .Internal() as in case of optim(), > uniroot(). > > Is there any way to > > (Q2a) find out a corresponding correct value for argument envir/pos in assign > ---on run-time---, i.e. how many layers of calls are between > myF() and myH()? > > --- my first guess was to use sys.frame() but I am not convinced... > > (Q2b) to make myH() when called from within a call to .Internal() > perform assignments in the environment of myF() > > ? > > Or should we proceed in a completely different way? > > Thank you already for your advice, > > Peter > > -------------------------------------------------------------------------- > --- Example: > > To given clipping height b, myH() calculates an "optimal" influence curve > which involves determining certain Lagrange multipliers in a fixed-point type > algorithm. > To determine b according to a certain criterium, moreover, myH() evaluates > a function H0 in b, the zero of which will be the "optimal" b. > > So to use notmyG()=uniroot() as zero-finder the return value of myH() > should be H0(b), while myF() should also get to know about the Lagrange > multipliers determined in myH(). > > ______________________________________________ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel > -- Luke Tierney Chair, Statistics and Actuarial Science Ralph E. Wareham Professor of Mathematical Sciences University of Iowa Phone: 319-335-3386 Department of Statistics and Fax: 319-335-3017 Actuarial Science 241 Schaeffer Hall email: [EMAIL PROTECTED] Iowa City, IA 52242 WWW: http://www.stat.uiowa.edu ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
