cover?(p1)
Returns true if obj is between the begin and end of the range.
This tests begin <= obj <= end when #exclude_end? is false and begin <= obj < end when #exclude_end? is true.
("a".."z").cover?("c") #=> true ("a".."z").cover?("5") #=> false ("a".."z").cover?("cc") #=> true
static VALUE range_cover(VALUE range, VALUE val) { VALUE beg, end; beg = RANGE_BEG(range); end = RANGE_END(range); return r_cover_p(range, beg, end, val); }