Generic, reusable, read-eval-print loop. By default, reads from *in*, writes to *out*, and prints exception summaries to *err*. If you use the default :read hook, *in* must either be an instance of LineNumberingPushbackReader or duplicate its behavior of both supporting .unread and collapsing CR, LF, and CRLF into a single \newline. Options are sequential keyword-value pairs. Available options and their defaults:
- :init, function of no arguments, initialization hook called with bindings for set!-able vars in place. default: #()
- :need-prompt, function of no arguments, called before each read-eval-print except the first, the user will be prompted if it returns true. default: (if (instance? LineNumberingPushbackReader *in*) #(.atLineStart *in*) #(identity true))
- :prompt, function of no arguments, prompts for more input. default: repl-prompt
- :flush, function of no arguments, flushes output default: flush
- :read, function of two arguments, reads from *in*: - returns its first argument to request a fresh prompt - depending on need-prompt, this may cause the repl to prompt before reading again - returns its second argument to request an exit from the repl - else returns the next object read from the input stream default: repl-read
- :eval, funtion of one argument, returns the evaluation of its argument default: eval
- :print, function of one argument, prints its argument to the output default: prn
- :caught, function of one argument, a throwable, called when read, eval, or print throws an exception or error default: repl-caught
; clojure/main.clj:113 (defn repl [& options] (let [{:keys [init need-prompt prompt flush read eval print caught] :or {init #() need-prompt (if (instance? LineNumberingPushbackReader *in*) #(.atLineStart *in*) #(identity true)) prompt repl-prompt flush flush read repl-read eval eval print prn caught repl-caught}} (apply hash-map options) request-prompt (Object.) request-exit (Object.) read-eval-print (fn [] (try (let [input (read request-prompt request-exit)] (or (#{request-prompt request-exit} input) (let [value (eval input)] (print value) (set! *3 *2) (set! *2 *1) (set! *1 value)))) (catch Throwable e (caught e) (set! *e e))))] (with-bindings (try (init) (catch Throwable e (caught e) (set! *e e))) (prompt) (flush) (loop [] (when-not (= (read-eval-print) request-exit) (when (need-prompt) (prompt) (flush)) (recur))))))
Copyright (c) Rich Hickey. All rights reserved.
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