call <- quote(f(a, b))
# Subsetting a call returns the arguments converted to a language
# object:
call[-1]
# On the other hand, call_args() returns a regular list that is
# often easier to work with:
str(call_args(call))
# When the arguments are unnamed, a vector of empty strings is
# supplied (rather than NULL):
call_args_names(call)
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