Evaluate call that contains another call (call within call)

Question

I have encountered a snippet of code where call contains another call. For example:

a <- 1
b <- 2
# First call
foo <- quote(a + a)
# Second call (call c         


        

Answer 1

Here's something that (at least partially) works:

evalception <- function (expr) {
    if (is.call(expr)) {
        for (i in seq_along(expr))
            expr[[i]] <- eval(evalception(expr[[i]]))
        eval(expr)
    }
    else if (is.symbol(expr)) {
        evalception(eval(expr))
    }
    else {
        expr
    }
}

It supports arbitrary nesting but will probably fail with objects of mode expression.

> a <- 1
> b <- 2
> # First call
> foo <- quote(a + a)
> # Second call (call contains another call)
> bar <- quote(foo ^ b)
> baz <- quote(bar * (bar + foo))
> sample <- quote(rnorm(baz, 0, sd=10))
> evalception(quote(boxplot.stats(sample)))
$stats
[1] -23.717520  -8.710366   1.530292   7.354067  19.801701

$n
[1] 24

$conf
[1] -3.650747  6.711331

$out
numeric(0)