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

I found a CRAN package that can do this - oshka: Recursive Quoted Language Expansion.

It recursively replaces quoted language calls by objects in environment.

a <- 1
b <- 2
foo <- quote(a + a)
bar <- quote(foo ^ b)

So call oshka::expand(bar) gives (a + a)^b and eval(oshka::expand(bar)) returns 4. It also works with more complicated calls that @Oliver suggested:

d <- 3
zz <- quote(bar + d)
oshka::expand(zz)
# (a + a)^b + d