sym() creates a symbol from a string and
syms() creates a list of symbols from a
character vector.
expr() and quo() quote
one expression. quo() wraps the quoted expression in a quosure.
The plural variants exprs() and
quos() return a list of quoted expressions or
quosures.
enexpr() and enquo()
capture the expression supplied as argument by the user of the
current function (enquo() wraps this expression in a quosure).
enexprs() and enquos()
capture multiple expressions supplied as arguments, including
....