在Clojure中按:type定制地图打印 [英] Customizing the printing of maps by :type in Clojure

问题描述

打印这张地图很丑陋:

  {:type :move,
   :name :boost,
   :from
   {:nodeid :plus,
    :name :left-operand,
    :value
    {:args [:result :right-operand],
     :f
     #object[fargish.workspace_test$fn__159675$fn__159678 0xb3f518f "fargish.workspace_test$fn__159675$fn__159678@b3f518f"]},
    :dockclass :input,
    :ref [:plus :left-operand]},
   :to
   {:nodeid :source11,
    :name :output,
    :value 11,
    :dockclass :output,
    :ref [:source11 :output]},
   :do
   #object[fargish.workspace$do_boost 0x179d226e "fargish.workspace$do_boost@179d226e"],
   :do-hypothetically
   #object[fargish.workspace$do_hypothetical_boost 0x68d6475a "fargish.workspace$do_hypothetical_boost@68d6475a"]}

大多数时候，我不需要看大部分.我希望它看起来像这样:

Most of the time, I don't need to see most of that. I'd like it to look something roughly like this:

#boost{:from [:plus :left-operand] :to [:source11 :output]}

Clojure是否提供了一个挂钩让我插入代码，以便如果地图的:type 键的值是:move ， str 会调用我编写的函数来生成字符串吗?

Does Clojure provide a hook to let me insert code so that if the value of a map's :type key is :move, str will call a function I write to generate the string?

我研究了 打印方法 .如果我正确理解的话，那将扩展派发自变量类型viz的多重方法.clojure.lang.PersistentArrayMap，而不是地图的:type .AFAIK，无法转发"到先前定义的多重方法，否则我可以为clojure.lang.PersistentArrayMap编写一个 print-method ，并查看:type 和如果其值不是:move ，则调用通用方法.

I've looked into print-method. If I understand it correctly, that would extend a multimethod that dispatches on the type of the argument, viz. clojure.lang.PersistentArrayMap, not the :type of the map. AFAIK, there's no way to "forward" to the previously defined multimethod, or else I could write a print-method for clojure.lang.PersistentArrayMap that looked at :type and then called the generic method if its value isn't :move.

即使只是自定义 pprint 也将有所帮助.从理论上讲， pprint 是非常可定制的，但是我还没有找到这不完整，表明 pprint 尚未真正完成.

Even just customizing pprint would be helpful. Theoretically, pprint is very customizable, but I haven't found documentation that explains how. This is incomplete and suggests that pprint isn't really done.

影响 pprint 的输出会很好，但并非绝对必要.仅仅能够影响 str 和 print 将会是一个很大的帮助.

Affecting the output of pprint would be nice but it isn't strictly necessary. Just being able to affect str and print would be a great help.

推荐答案

打印方法

print-method already looks at the :type key on the metadata of your object. Just arrange for :type to be in the metadata rather than (or in addition to) the actual map itself, and you can define your own print-method.

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