diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/clj/clojure/core.clj | 12 |
1 files changed, 9 insertions, 3 deletions
diff --git a/src/clj/clojure/core.clj b/src/clj/clojure/core.clj index dc606274..e0ebaf65 100644 --- a/src/clj/clojure/core.clj +++ b/src/clj/clojure/core.clj @@ -873,8 +873,12 @@ ;;map stuff (defn contains? - "Returns true if key is present, else false." - [map key] (. clojure.lang.RT (contains map key))) + "Returns true if key is present in the given collection, otherwise + returns false. Note that for numerically indexed collections like + vectors and Java arrays, this tests if the numeric key is within the + range of indexes. 'contains?' operates constant or logarithmic time; + it will not perform a linear search for a value. See also 'some'." + [coll key] (. clojure.lang.RT (contains coll key))) (defn get "Returns the value mapped to key, not-found or nil if key not present." @@ -1349,7 +1353,9 @@ (defn some "Returns the first logical true value of (pred x) for any x in coll, - else nil." + else nil. One common idiom is to use a set as pred, for example + this will return true if :fred is in the sequence, otherwise nil: + (some #{:fred} coll)" [pred coll] (when (seq coll) (or (pred (first coll)) (recur pred (rest coll))))) |