many: many matches 0 or more of pattern p. In BNF notation,
repetition occurs often enough to merit its own abbreviation. When zero or
more repetitions of a phrase p are admissible, we simply write
p*. The many combinator corresponds directly to this operator,
and is defined in much the same way.
Description
This implementation of many differs from (Hutton92) due to the nature
of R's data structures. Since R does not support the concept of a list of
tuples, we must revert to using a list rather than a vector, since all values
in an R vector must be the same datatype.