Hello,

I'm trying to access an object, given only its name as a symbol.  I cannot
figure out how to proceed.  Suppose I call substitute( ) on the expression
'x + 2':

> parse.tree <- substitute(x + 2);

The constituents of parse.tree are of type symbol and numeric:

> str(parse.tree[[1]])
symbol +

> str(parse.tree[[2]])
symbol x

> str(parse.tree[[3]])
num 2

Suppose that x is S4 object, and that I need to access a slot of that
object.  How can I do so, using only 'parse.tree' (or parse.tree coerced
into a list)?

Thanks, Patrick

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