If language A is a subset of language B it doesn't follow that parsing B is strictly harder. This is not guaranteed. Consider two languages: 1. Some number o

If language A is a subset of language B it doesn't follow that parsing B is strictly harder. This is not guaranteed. Consider two languages: 1. Some number of "a" followed by the same number of "b". For example, aaabbb but not aabbb. 2. Any number of "a" followed by any number of "b". For example, aabbb but not aba. In this case (1) is a subset of (2), but parsing (2) is easier than parsing (1) since in (1) you have to verify that the numbers match (which, in technical terms, means its not regular).