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[Rcpp-devel] C++ version of lapply using std::transform

Romain Francois 
Hello,

I've just commited some code that allows iterating over generic and 
expression vectors (Rcpp::GenericVector and Rcpp::ExpressionVector).

This allows to write for example a c++ version of lapply (without the 
handling of the ellipsis (...) ) using the std::transform algorithm from 
the STL :

cpp_lapply <- cfunction(signature(x = "list", g = "function" ), '
		Function fun(g) ;
		List input(x) ;
		List output( input.size() ) ;
		std::transform( input.begin(), input.end(), output.begin(), fun ) ;
		output.names() = input.names() ;
		return output ;
	
	', Rcpp = TRUE, includes = "using namespace Rcpp;"  )
	

 > data <- list( x = letters, y = LETTERS, z = 1:4 )
 > cpp_lapply( data, length )
$x
[1] 26

$y
[1] 26

$z
[1] 4

Have fun !

Romain