[R] The 'variables' attribute of terms()

[bluesky315 at gmail.com]

I got the following output when I try the code at the end.

> str(attr(terms1, 'variables'))
 language list(skips, Panel, Opening)
> class(attr(terms1, 'variables'))
[1] "call"

I checked ?call, where 'call' is a function. Could somebody let me
know what a 'call' class is and what 'language' is?

##########
form1=skips ~ Panel * Opening
terms1=terms(form1)
str(attr(terms1, 'variables'))
class(attr(terms1, 'variables'))