Emacs: gethash doesn't see key in hashtable

Question

I evaluated the following elisp code in ielm:

(setq foo-hash (make-hash-table))

(puthash "location" "house" foo-hash)

(defun foo-start ()
  (interactive)
  (message (gethash "location" foo-hash)))

However when i run (foo-start) or (gethash "location" foo-hash) i get only nil echoed. Entering just foo-hash in ielm echoes: #s(hash-table size 65 test eql rehash-size 1.5 rehash-threshold 0.8 data ("location" "house"))

Is that a bug or i am doing something wrong?

Emacs version: 24.0.95.1

Answer 1

Hash tables in elisp use eql for comparison by default. Strings won't be equal with eql unless they're the same object. You probably want to use equal, which compares the contents of the strings. Create your hash table with this:

(make-hash-table :test 'equal)