How do you add in this hash table in Clojure?
I have a document hash which is a reference like this:
(def *document-hash* (ref (hash-map)))
It looks like this
{"documentid" {:term-detail {"term1" count1 ,"term2" count2}, "doclen" 33}}}
How do I add to this hash table?Right now I have
(defn add-doc-hash [docid term-number count]
(dosync (alter *document-hash*
(fn [a-hash]
(assoc a-hash docid {:term-detail
(assoc ((a-hash docid)) :term-detail) term-number count), :doclen 33))))))
- I want to update the term-details for the documents
- Every time a new term comes, I want to get the term-details开发者_如何学Python and update the terms and its count
- initially the hash is empty
But this throws the null pointer exception because ther term-detail hash is not created when I try to add the term-number.
user> (def x (ref {"documentid" {:term-detail {"term1" 1 ,"term2" 2}, "doclen" 33}}))
#'user/x
user> (dosync (alter x assoc-in ["documentid" :term-detail "term3"] 0))
{"documentid" {:term-detail {"term3" 0, "term1" 1, "term2" 2}, "doclen" 33}}
user> (dosync (alter x update-in ["documentid" :term-detail "term3"] inc))
{"documentid" {:term-detail {"term3" 1, "term1" 1, "term2" 2}, "doclen" 33}}
Here's a rewrite of your function that should work. It uses the assoc-in function
(defn add-doc-hash [docid term-number count]
(dosync (alter *document-hash* assoc-in [docid :term-detail term-number] count)))
Another way of phrasing the question if i understand it correctly would be: "how do i write a function to add another [term, count] pair to a map."
a little helper function to get the current details for a map, if that map is not yet added, then clearly it will have no details so i represent this with an empty map
this solves your problem of where to add the first term-number:
(defn get-term-detail [a-hash docid]
(let [entry (a-hash docid)]
(if nil? entry)
{}
(:term-details entry))))
then soemthing like:
(assoc a-hash docid {:term-details (assoc (get-term-detail a-hash docid) term-number count) :doclen 33)
to actuall add it to the hash
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