Terms of a sum in a R expression

Question

Given a R expression which represents a sum of terms like

expr <- expression(a + b * c + d + e * f)

I would like to retrieve the set of all the t

Answer 1

Try recursively parsing the expression:

getTerms <- function(e, x = list()) {
  if (is.symbol(e)) c(e, x)
  else if (identical(e[[1]], as.name("+"))) Recall(e[[2]], c(e[[3]], x))
  else c(e, x)
}

expr <- expression(a + b * c + d + e * (f + g))
getTerms(expr[[1]])

giving:

[[1]]
a

[[2]]
b * c

[[3]]
d

[[4]]
e * (f + g)