R devel - Nov 2009 - A fix that for 'bquote' that may work (PR#14031)

This is a fix for 'bquote' that may work.

function (expr, where =3D parent.frame())=20
{
    unquote <- function(e) {
        if (length(e) <=3D 1 || !is.language(e))=20
            e
        else if (e[[1]] =3D=3D as.name("."))=20
            eval(e[[2]], where)
        else as.call(lapply(e, unquote))
    }
    unquote(substitute(expr))
}
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On Thu, 5 Nov 2009, suharto_anggono at yahoo.com wrote:
> This is a fix for 'bquote' that may work.
>
> function (expr, where =3D parent.frame())=20
> {
>    unquote <- function(e) {
>        if (length(e) <=3D 1 || !is.language(e))=20
>            e
>        else if (e[[1]] =3D=3D as.name("."))=20
>            eval(e[[2]], where)
>        else as.call(lapply(e, unquote))
>    }
>    unquote(substitute(expr))
> }
If you want to use bquote() on function definitions a better fix is

bquote <- function (expr, where = parent.frame())
{
     unquote <- function(e) {
         if (length(e) <= 1)
             e
         else if (e[[1]] == as.name("."))
             eval(e[[2]], where)
         else if (is.pairlist(e)){
             as.pairlist(lapply(e,unquote))
         }
         else as.call(lapply(e, unquote))
     }
     unquote(substitute(expr))
}

since that now allows substitution into default arguments, eg
   default<-1
   g<-b2quote(function(x,y=.(default)) x+y )



         -thomas

Thomas Lumley			Assoc. Professor, Biostatistics
tlumley at u.washington.edu	University of Washington, Seattle