clojure.core/print-method

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Type: var Added: Clojure unknown Examples: 2 Runnable: 0

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Examples

by pangloss on 2013-05-31 . May have evaluation errors. ▶

(deftype XYZ []) ; without custom print-method defined: (prn (XYZ.)) #<XYZ user.XYZ@2670d85b> (defmethod print-method XYZ [v ^java.io.Writer w] (.write w "<<-XYZ->>")) ; with print-method (prn (XYZ.)) <<-XYZ->>

by reborg on 2021-04-11 . May have evaluation errors. ▶

(import '[java.net URL] [java.io File]) ;; Extends pr-str to URL objects with a form suitable for ;; read-string to read back into an URL with the related ;; https://clojuredocs.org/clojure.core/*data-readers* binding: (defmethod print-method URL [url writer] (doto writer (.write "#url ") (.write "\"") (.write (.toString url)) (.write "\""))) (-> "/etc/hosts" File. .toURL pr-str) ;; "#url \"file:/etc/hosts\""

Note by mrzor

Take care when writing things that look like a reader macro, like #mything<42 42 42>. It may break your AOT compilations with a java.lang.RuntimeException: No reader function for tag mything.

A quick workaround is not to emit a # character. The thorough solution starts by reading https://clojuredocs.org/clojure.core/data-readers and is beyond the scope of this note.

See also

• clojure.core/print-dup (1)

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