Problems with CRAN package Ryacas

On Mon, Apr 9, 2012 at 2:47 PM, Martin Maechler
<maechler at stat.math.ethz.ch> wrote:

Apropos:

I don't have the problems, the OP had, but on my ubuntu
notebook, Ryacas does not return expressions (just the strings),
and hence

? ?as.expression( <yacas-result> )

always gives NULL ?and e.g. the ? demo(Ryacas-Function)
also fails:

?> yacas(expression(deriv(BurrCDF(x,c,k))))
?k*c*x^(c-1)*(x^c+1)^(-(k+1));
?> yy <- yacas(expression(deriv(BurrCDF(x,c,k))))
?> yy
?k*c*x^(c-1)*(x^c+1)^(-(k+1));
?> str(yy)
?List of 2
?$ ? ? ? ? ?: NULL
?$ YacasForm: chr "k*c*x^(c-1)*(x^c+1)^(-(k+1));"
?- attr(*, "class")= chr "yacas"
?>

I have

- yacas 1.2.2 ?(standard ubuntu package)

The latest version of Ryacas on CRAN is 0.2-11
http://cran.r-project.org/package=Ryacas

yacas("Version()")