
208 R Programming for Bioinformatics
this function is available through the RBioinf package. Try a more complex
evaluation, say adding together values for x and y.
SEXP evalExpr(SEXP expr, SEXP rho)
{
return(eval(expr, rho))
}
Program 6.9: Pseudo-code showing how to evaluate an expression in C.
6.6.2.3 Constructing function calls
In R, there are essentially two types of lists: the one used most often at
the R level is essentially a generic vector, while the other is a Lisp-style list
that is sometimes referred to as a pairlist. While seldom used at the R level,
most of R’s internals are written using pairlists. And in particular, this is the
internal representation ...