First, why does this expression have a 'srcref' element: > exprA <- substitute(function(x) a*x, list(a=2)) > print(exprA) function(x) 2 * x > str(as.list(exprA)) List of 4 $ : symbol function $ :Dotted pair list of 1 ..$ x: symbol $ : language 2 * x $ :Class 'srcref' atomic [1:8] 1 20 1 34 20 34 1 1 .. ..- attr(*, "srcfile")=Classes 'srcfilecopy', 'srcfile' <environment: 0x00000000111feaf8>
whereas this does not: > exprB <- substitute(a*x, list(a=2)) > print(exprB) 2 * x > str(as.list(exprB)) List of 3 $ : symbol * $ : num 2 $ : symbol x Second, what is the proper way to drop that 'srcref' element in 'exprA'? I can think of either exprC <- exprA exprC[[4L]] <- NULL or exprC <- parse(text=deparse(exprA)) Anything better/safer? BACKGROUND: The reason for this is that I wish to create a function dynamically via variable substitution such that when printed, the function displays the substituted values, e.g. > fcnA <- eval(exprA) > print(fcnA) function(x) a*x versus > fcnC <- eval(exprC) > print(fcnC) function(x) 2 * x Thanks, Henrik ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
