Is (eq? '() '()) guaranteed to be true in Racket?
If not mistaken, two empty lists are guaranteed to be eq? in R7RS, but I want to know if Racket also provides such a guarantee.
I have read the documentation, but I couldn't find the answer.
Are two empty lists guaranteed to be 'eq?' in Racket?
Viewed 48
1 Answers
Yes. The behaviour of eq? more or less follows eq? from Scheme.
The documentation on eq? could be clearer though. The documentation on lists has the following to say:
A list is recursively defined: it is either the constant null, or it is a pair whose second value is a list.
So the empty list is a constant - which means it is unique.
Related