为什么clojure中的map返回异步chan而不是字符串序列？

Question

I am new to clojure and currently stuck with the map function.I tried the following code:

(map #(str "Hello " % "!" ) ["Ford" "Arthur" "Tricia"])

it's returning:

#object[clojure.core.async.impl.channels.ManyToManyChannel 0x2eaf8b7c "clojure.core.async.impl.channels.ManyToManyChannel@2eaf8b7c"]

though i wanted:

("Hello Ford!" "Hello Arthur!" "Hello Tricia!"])

I was following the clojure.core/map documentation example but it isn't working as expected..

Answer 1

It looks like you have probably replaced clojure.core/map with clojure.core.async/map . The most common way this would happen is by doing something at your repl like this (note the many warnings that tell you about this when you do so):

user=> (use 'clojure.core.async)
WARNING: reduce already refers to: #'clojure.core/reduce in namespace: user, being replaced by: #'clojure.core.async/reduce
WARNING: take already refers to: #'clojure.core/take in namespace: user, being replaced by: #'clojure.core.async/take
WARNING: map already refers to: #'clojure.core/map in namespace: user, being replaced by: #'clojure.core.async/map
WARNING: transduce already refers to: #'clojure.core/transduce in namespace: user, being replaced by: #'clojure.core.async/transduce
WARNING: into already refers to: #'clojure.core/into in namespace: user, being replaced by: #'clojure.core.async/into
WARNING: partition already refers to: #'clojure.core/partition in namespace: user, being replaced by: #'clojure.core.async/partition
WARNING: merge already refers to: #'clojure.core/merge in namespace: user, being replaced by: #'clojure.core.async/merge
WARNING: partition-by already refers to: #'clojure.core/partition-by in namespace: user, being replaced by: #'clojure.core.async/partition-by

You can always refer unambiguously to a function with it's qualified name:

(clojure.core/map #(str "Hello " % "!" ) ["Ford" "Arthur" "Tricia"])

Generally, though it's best to avoid using use and instead require the other namespace and give it an alias instead:

(require '[clojure.core.async :as async])

That way, your clojure.core/map can still be used as map (as all clojure.core functions are auto-referred) and the async version can be referred to as async/map .