A few demonstrations of Rcpp::InternalFunction

Makefile

## -*- mode: make; tab-width: 8; -*-
##
## Simple Makefile
##
## From RInside examples 
## TODO: 
##  proper configure for non-Debian file locations,   [ Done ]
##  allow RHOME to be set for non-default R etc

## comment this out if you need a different version of R, 
## and set set R_HOME accordingly as an environment variable
R_HOME := 		$(shell R RHOME)

sources := 		$(wildcard *.cpp)
programs := 		$(sources:.cpp=)


## include headers and libraries for R 
RCPPFLAGS := 		$(shell $(R_HOME)/bin/R CMD config --cppflags)
RLDFLAGS := 		$(shell $(R_HOME)/bin/R CMD config --ldflags)
RBLAS := 		$(shell $(R_HOME)/bin/R CMD config BLAS_LIBS)
RLAPACK := 		$(shell $(R_HOME)/bin/R CMD config LAPACK_LIBS)

## if you need to set an rpath to R itself, also uncomment
#RRPATH :=		-Wl,-rpath,$(R_HOME)/lib

## include headers and libraries for Rcpp interface classes
RCPPINCL := 		$(shell echo 'Rcpp:::CxxFlags()' | $(R_HOME)/bin/R --vanilla --slave)
RCPPLIBS := 		$(shell echo 'Rcpp:::LdFlags()'  | $(R_HOME)/bin/R --vanilla --slave)


## include headers and libraries for RInside embedding classes
RINSIDEINCL := 		$(shell echo 'RInside:::CxxFlags()' | $(R_HOME)/bin/R --vanilla --slave)
RINSIDELIBS := 		$(shell echo 'RInside:::LdFlags()'  | $(R_HOME)/bin/R --vanilla --slave)

## compiler etc settings used in default make rules
CXX := 			$(shell $(R_HOME)/bin/R CMD config CXX)
CPPFLAGS := 		-Wall $(shell $(R_HOME)/bin/R CMD config CPPFLAGS)
CXXFLAGS := 		$(RCPPFLAGS) $(RCPPINCL) $(RINSIDEINCL) $(shell $(R_HOME)/bin/R CMD config CXXFLAGS)
LDLIBS := 		$(RLDFLAGS) $(RRPATH) $(RBLAS) $(RLAPACK) $(RCPPLIBS) $(RINSIDELIBS)

all: 			$(programs)
			@test -x /usr/bin/strip && strip $^

run:			$(programs)
			@for p in $(programs); do echo; echo "Running $$p:"; ./$$p; done

clean:
			rm -vf $(programs)
			rm -vrf *.dSYM

runAll:
			for p in $(programs); do echo "Running $$p"; ./$$p; done

sjb_rinside_ex1.cpp

// -*- mode: C++; c-indent-level: 4; c-basic-offset: 4;  tab-width: 8; -*-
//
// A few more examples of exposing C++ functions to R
//
// Copyright (C) 2012 Stephen Jeffrey Barr

#include <RInside.h>                    // for the embedded R via RInside

// a c++ function we wish to expose to R
const char* hello( std::string who ){
        std::string result( "hello " ) ;
        result += who ;
        return result.c_str() ;
} 

const double doubler( double input ){   
    return 2.0 * input;
} 

const double ary_sum( const Rcpp::NumericVector & input ){   
    double asum = 0.0;
    int len = input.size();
    for(int i = 0; i < len; i++) {
	asum += input[i];
    }
    return asum;
} 


// NOTE, this assumes that the input vector is length 2
const double my_objective_fn( const Rcpp::NumericVector & input ){   
    double asum = 0.0;
    asum = ((input[0] - 3.0)*(input[0] - 3.0)) + 
	((input[1] - 5.5)*(input[1] - 5.5));
    return asum;
} 



int main(int argc, char *argv[]) {

    // create an embedded R instance
    RInside R(argc, argv);               

    // expose the "hello" function in the global environment
    R["hello"] = Rcpp::InternalFunction( &hello ) ;
    R["doubler"] = Rcpp::InternalFunction( &doubler );
    R["ary_sum"] = Rcpp::InternalFunction( &ary_sum );
    R["my_objective_fn"] = Rcpp::InternalFunction( &my_objective_fn );

    // call it and display the result
    std::string result = R.parseEval("hello('world')") ;
    std::cout << "hello( 'world') =  " << result << std::endl ; 

    // Use the doubler function
    double ans = R.parseEval("doubler(3.0)");
    std::cout << "doubler(3.0) =  " << ans << std::endl ; 

    // Get the sum of an array in C++
    ans = R.parseEval("ary_sum(c(3.0, 4.5, 2.1,1.5))");
    std::cout << "ary_sum(c(3.0, 4.5, 2.1,1.5)) =  " << ans << std::endl ; 

    // Evaluate my_objective_fn
    ans = 0.0;
    ans = R.parseEval("my_objective_fn(c(1.0, 2.0))");
    std::cout << "my_objective_fn(c(1.0, 2.0)) =  " << ans << std::endl ; 

    // Optimize my_objective_fn
    Rcpp::List x = R.parseEval("optim(c(.2,.8), my_objective_fn)");
    Rcpp::NumericVector optimum_point = Rcpp::as<Rcpp::NumericVector>(x[0]);
    std::cout << "OPT.0: " << optimum_point(0) << std::endl;
    std::cout << "OPT.1: " << optimum_point(1) << std::endl;


    exit(0);
}