Does an empty string fulfill the condition 'the string can contain alphabet and number only'?

Question

On one hand, an empty string doesn't contain any alphabet and number, which looks violate the condition 'contain alphabet and number', on other hand, the opposite of the condition is 'contain non-alphabet and non-numeric characters', which an empty string doesn't contain any, and should fulfill the condition. Does the empty fulfill the condition?

Answer 1

It depends exactly how you phrase the condition.

The empty string does satisfy the condition, "Contains nothing other than numbers and letters."

However, it does not satisfy the condition, "Contains numbers and/or letters, and nothing but numbers and letters."

The latter condition has a positive component, while the former does not.

This becomes a problem in natural language, because some people would interpret "contains only numbers and letters" as as meaning that the string does have to contain something; however, I think this is the minority view. Bottom line, though, this is why we need to be careful to state all conditions clearly.