core_deftype.clj

;   Copyright (c) Rich Hickey. All rights reserved.
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(in-ns 'clojure.core)

;;;;;;;;;;;;;;;;;;;;;;;;;;;; defclass/deftype ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

(defn hash-combine [x y] 
  (clojure.lang.Util/hashCombine x (clojure.lang.Util/hash y)))

(defn- emit-deftype* 
  "Do not use this directly - use deftype"
  [tagname name fields interfaces methods]
  (let [tag (keyword (str *ns*) (str tagname))
        classname (symbol (str *ns* "." name))
        interfaces (vec interfaces)
        interface-set (set (map resolve interfaces))
        methodname-set (set (map first methods))
        dynamic-type (contains? interface-set clojure.lang.IDynamicType)
        implement? (fn [iface] (not (contains? interface-set iface)))
        hinted-fields fields
        fields (vec (map #(with-meta % nil) fields))
        base-fields fields
        fields (conj fields '__meta '__extmap)]
    (letfn 
     [(eqhash [[i m]] 
        (if (not (or (contains? methodname-set '.equals) (contains? methodname-set '.hashCode)))
          [i
           (conj m 
                 `(.hashCode [] (-> ~tag hash ~@(map #(list `hash-combine %) (remove #{'__meta} fields))))
                 `(.equals [~'o] 
                    (boolean 
                     (or (identical? ~'this ~'o)
                         (when (instance? clojure.lang.IDynamicType ~'o)
                           (let [~'o ~(with-meta 'o {:tag 'clojure.lang.IDynamicType})]
                             (and (= ~tag (.getDynamicType ~'o)) 
                                  ~@(map (fn [fld] `(= ~fld (.getDynamicField ~'o ~(keyword fld) ~'this))) base-fields)
                                  (= ~'__extmap (.getExtensionMap ~'o)))))))))]
          [i m]))
      (iobj [[i m]] 
        (if (and (implement? clojure.lang.IObj) (implement? clojure.lang.IMeta))
          [(conj i 'clojure.lang.IObj)
           (conj m `(.meta [] ~'__meta)
                 `(.withMeta [~'m] (new ~tagname ~@(replace {'__meta 'm} fields))))]
          [i m]))
      (ilookup [[i m]] 
        (if (not (methodname-set '.valAt))
          [(conj i 'clojure.lang.ILookup 'clojure.lang.IKeywordLookup)
           (conj m `(.valAt [k#] (.valAt ~'this k# nil))
                 `(.valAt [k# else#] 
                    (case k# ~@(mapcat (fn [fld] [(keyword fld) fld]) 
                                                   base-fields)
                           (get ~'__extmap k# else#)))
                 `(.getLookupThunk [k#]
                    (case k#
                          ~@(mapcat 
                             (fn [fld]
                               (let [cstr (str (clojure.core/name classname) "$__lookup__" (clojure.core/name fld))]
                                 [(keyword fld) 
                                  `(-> ~cstr (Class/forName) (.newInstance))]))
                             base-fields)
                          nil)))]
          [i m]))
      (idynamictype [[i m]]
        [(conj i 'clojure.lang.IDynamicType)
         (conj m
               `(.getDynamicType [] ~tag)
               `(.getExtensionMap [] ~'__extmap)
               `(.getDynamicField [k# else#] 
                  (condp identical? k# ~@(mapcat (fn [fld] [(keyword fld) fld]) base-fields)
                         (get ~'__extmap k# else#))))])
      (imap [[i m]] 
         (if (and (interface-set clojure.lang.IPersistentMap) (not (methodname-set '.assoc)))
           [i
            (conj m 
                  `(.count [] (+ ~(count base-fields) (count ~'__extmap)))
                  `(.empty [] (throw (UnsupportedOperationException. (str "Can't create empty: " ~(str classname)))))
                  `(.cons [e#] (let [[k# v#] e#] (.assoc ~'this k# v#)))
                  `(.equiv [o#] (.equals ~'this o#))
                  `(.containsKey [k#] (not (identical? ~'this (.valAt ~'this k# ~'this))))
                  `(.entryAt [k#] (let [v# (.valAt ~'this k# ~'this)]
                                     (when-not (identical? ~'this v#)
                                       (clojure.lang.MapEntry. k# v#))))
                  `(.seq [] (concat [~@(map #(list `new `clojure.lang.MapEntry (keyword %) %) base-fields)] 
                                     ~'__extmap))
                  (let [gk (gensym) gv (gensym)]
                    `(.assoc [~gk ~gv]
                       (condp identical? ~gk
                         ~@(mapcat (fn [fld]
                                     [(keyword fld) (list* `new tagname (replace {fld gv} fields))])
                                   base-fields)
                         (new ~tagname ~@(remove #{'__extmap} fields) (assoc ~'__extmap ~gk ~gv)))))
                  `(.without [k#] (if (contains? #{~@(map keyword base-fields)} k#)
                                     (dissoc (with-meta (into {} ~'this) ~'__meta) k#)
                                     (new ~tagname ~@(remove #{'__extmap} fields) 
                                          (not-empty (dissoc ~'__extmap k#))))))]
           [i m]))]
     (let [[i m] (-> [interfaces methods] eqhash iobj ilookup imap idynamictype)]
       `(deftype* ~tagname ~classname ~(conj hinted-fields '__meta '__extmap) 
          :implements ~(vec i) 
          ~@m)))))

(defmacro deftype
  "Alpha - subject to change
  
  Dynamically generates compiled bytecode for an anonymous class with
  the given fields, and, optionally, interfaces and methods. The Name
  will be used to create a dynamic type tag keyword of the
  form :current.ns/Name. This tag will be returned from (type
  an-instance). 

  A factory function of current.ns/Name will be defined,
  overloaded on 2 arities, the first taking the designated fields in
  the same order specified, and the second taking the fields followed
  by a metadata map (nil for none) and an extension field map (nil for
  none). 

  The class will have the (immutable) fields named by fields, which
  can have type hints. Interfaces and methods are optional. The only
  methods that can be supplied are those declared in the interfaces.
  'this' is impliclty bound to the target object (i.e. same meaning as
  in Java). Note that method bodies are not closures, the local
  environment includes only the named fields, and those fields can be
  accessed directy, i.e. with just foo, instead of (.foo this).

  Method definitions take the form:

  (.methodname [args] body) ;note the dot on the methodname!

  The argument and return types can be hinted on the arg and
  methodname symbols. If not supplied, they will be inferred, so type
  hints should be reserved for disambiguation.

  In the method bodies, the (unqualified) name can be used to name the
  class (for calls to new, instance? etc).

  The class will have implementations of two (clojure.lang) interfaces
  generated automatically: IObj (metadata support), ILookup (get and
  keyword lookup for fields). If you specify IPersistentMap as an
  interface, but don't define methods for it, an implementation will
  be generated automatically.

  In addition, unless you supply a version of .hashCode or .equals,
  deftype/class will define type-and-value-based equality and hashCode.

  When AOT compiling, generates compiled bytecode for a class with the
  given name (a symbol), prepends the current ns as the package, and
  writes the .class file to the *compile-path* directory. When
  dynamically evaluated, the class will have a generated name.

  Two constructors will be defined, one taking the designated fields
  followed by a metadata map (nil for none) and an extension field
  map (nil for none), and one taking only the fields (using nil for
  meta and extension fields)."

  [name [& fields] & [[& interfaces] & methods]]
  (let [gname (if *compile-files* name (gensym (str name "__")))
        classname (symbol (str *ns* "." gname))
        tag (keyword (str *ns*) (str name))
        hinted-fields fields
        fields (vec (map #(with-meta % nil) fields))]
    `(do
       ~(emit-deftype* name gname (vec hinted-fields) (vec interfaces) methods)
       (defmethod print-method ~tag [o# w#]
         ((var print-deftype) ~(vec (map #(-> % str keyword) fields)) o# w#))
       (defn ~name
         ([~@fields] (new ~classname ~@fields nil nil))
         ([~@fields meta# extmap#] (new ~classname ~@fields meta# extmap#))))))

(defn- print-deftype [fields, #^clojure.lang.IDynamicType o, #^Writer w]
  (print-meta o w)
  (.write w "#:")
  (.write w (str (name (.getDynamicType o))))
  (print-map
    (concat
      (map #(clojure.lang.MapEntry. % (.getDynamicField o % nil)) fields)
      (.getExtensionMap o))
    pr-on w))


;;;;;;;;;;;;;;;;;;;;;;; protocols ;;;;;;;;;;;;;;;;;;;;;;;;

(defn- expand-method-impl-cache [#^clojure.lang.MethodImplCache cache c f]
  (let [cs (into {} (remove (fn [[c f]] (nil? f)) (map vec (partition 2 (.table cache)))))
        cs (assoc cs c f)
        [shift mask] (min-hash (keys cs))
        table (make-array Object (* 2 (inc mask)))
        table (reduce (fn [#^objects t [c f]]
                        (let [i (* 2 (int (shift-mask shift mask (hash c))))]
                          (aset t i c)
                          (aset t (inc i) f)
                          t))
                      table cs)]
    (clojure.lang.MethodImplCache. (.protocol cache) (.methodk cache) shift mask table)))

(defn- super-chain [#^Class c]
  (when c
    (cons c (super-chain (.getSuperclass c)))))

(defn find-protocol-impl [protocol x]
  (if (and (:on protocol) (instance? (:on protocol) x))
    x
  (let [t (type x)
        c (class x)
        impl #(get (:impls protocol) %)]
    (or (impl t)
        (impl c)
        (and c (or (first (remove nil? (map impl (butlast (super-chain c)))))
                   (first (remove nil? (map impl (disj (supers c) Object))))
                     (impl Object)))))))

(defn find-protocol-method [protocol methodk x]
  (get (find-protocol-impl protocol x) methodk))

(defn extends? 
  "Returns true if atype explicitly extends protocol"
  [protocol atype]
  (when (get (:impls protocol) atype) true))

(defn extenders 
  "Returns a collection of the types explicitly extending protocol"
  [protocol]
  (keys (:impls protocol)))

(defn satisfies? 
  "Returns true if x satisfies the protocol"
  [protocol x]
  (when
      (or (and (:on protocol) (instance? (:on protocol) x))
          (find-protocol-impl protocol x))
    true))

(defn -cache-protocol-fn [#^clojure.lang.AFunction pf x]
  (let [cache  (.__methodImplCache pf)
        f (find-protocol-method (.protocol cache) (.methodk cache) x)]
    (when-not f
      (throw (IllegalArgumentException. (str "No implementation of method: " (.methodk cache) 
                                             " of protocol: " (:var (.protocol cache)) 
                                             " found for class: " (if (nil? x) "nil" (.getName (class x)))))))
    (set! (.__methodImplCache pf) (expand-method-impl-cache cache (class x) f))
    f))

(defn- emit-method-builder [on-interface method on-method arglists]
  (let [methodk (keyword method)
        gthis (with-meta (gensym) {:tag 'clojure.lang.AFunction})]
    `(fn [cache#]
       (let [#^clojure.lang.AFunction f#
             (fn ~gthis
               ~@(map 
                  (fn [args]
                    (let [gargs (map #(gensym (str "g__" % "__")) args)
                          target (first gargs)]
                      `([~@gargs]
                          (~@(if on-interface
                               `(if (instance? ~on-interface ~target)
                                  (. ~(with-meta target {:tag on-interface})  ~(or on-method method) ~@(rest gargs)))
                               `(do))
                          (let [cache# (.__methodImplCache ~gthis)]
                            (if (clojure.lang.Util/identical (clojure.lang.Util/classOf ~target)
                                                             (.lastClass cache#))
                              ((.lastImpl cache#) ~@gargs)
                              (let [f# (or (.fnFor cache# (clojure.lang.Util/classOf ~target))
                                           (-cache-protocol-fn ~gthis ~target))]
                                 (f# ~@gargs))))))))
                  arglists))]
         (set! (.__methodImplCache f#) cache#)
         f#))))

(defn -reset-methods [protocol]
  (doseq [[#^clojure.lang.Var v build] (:method-builders protocol)]
    (let [cache (clojure.lang.MethodImplCache. protocol (keyword (.sym v)))]
      (.bindRoot v (build cache)))))

(defn- assert-same-protocol [protocol-var method-syms]
  (doseq [m method-syms]
    (let [v (resolve m)
          p (:protocol (meta v))]
      (when-not (or (nil? v) (= protocol-var p))
        (binding [*out* *err*]
          (println "Warning: protocol" protocol-var "is overwriting"
                   (if p
                     (str "method " (.sym v) " of protocol " (.sym p))
                     (str "function " (.sym v)))))))))

(defn- emit-protocol [name opts+sigs]
  (let [[opts sigs]
        (loop [opts {:on nil} sigs opts+sigs]
          (condp #(%1 %2) (first sigs) 
            string? (recur (assoc opts :doc (first sigs)) (next sigs))
            keyword? (recur (assoc opts (first sigs) (second sigs)) (nnext sigs))
            [opts sigs]))
        sigs (reduce (fn [m s]
                       (let [mname (with-meta (first s) nil)
                             arglists (if (vector? (second s)) (list (second s)) (second s))
                             fx (nth s 2 nil)
                             doc (when (string? fx) fx)
                             mopts (apply hash-map (nthnext s (if (string? fx) 3 2)))]
                         (when (some #{0} (map count arglists))
                           (throw (IllegalArgumentException. (str "Protocol fn: " mname " must take at least one arg"))))
                         (assoc m (keyword mname) 
                                (merge mopts 
                                       {:name (vary-meta mname assoc :doc doc :arglists arglists)
                                        :arglists arglists
                                        :doc doc}))))
                     {} sigs)]
  `(do
     (defonce ~name {})
     (alter-meta! (var ~name) assoc :doc ~(:doc opts))
     (#'assert-same-protocol (var ~name) '~(map :name (vals sigs)))
     (alter-var-root (var ~name) merge 
                     (assoc ~opts 
                       :sigs '~sigs 
                       :var (var ~name)
                       :method-map 
                         ~(and (:on opts)
                               (apply hash-map 
                                      (mapcat 
                                       (fn [s] 
                                         [(keyword (:name s)) (keyword (or (:on s) (:name s)))])
                                       (vals sigs))))
                       :method-builders 
                        ~(apply hash-map 
                                (mapcat 
                                 (fn [s] 
                                   [`(intern *ns* (with-meta '~(:name s) {:protocol (var ~name)}))
                                    (emit-method-builder (:on opts) (:name s) (:on s) (:arglists s))])
                                 (vals sigs)))))
     (-reset-methods ~name)
     '~name)))

(defmacro defprotocol 
  "A protocol is a named set of named methods and their signatures:
  (defprotocol AProtocolName

  ;optional doc string
  \"A doc string for AProtocol abstraction\"

  ;method signatures
  (bar [a b] \"bar docs\")
  (baz ([a] [a b] [a b & c]) \"baz docs\"))

  No implementations are provided. Docs can be specified for the
  protocol overall and for each method. The above yields a set of
  polymorphic functions and a protocol object. All are
  namespace-qualified by the ns enclosing the definition The resulting
  functions dispatch on the type of their first argument, and thus
  must have at least one argument. defprotocol is dynamic, has no
  special compile-time effect, and defines no new types or classes
  Implementations of the protocol methods can be provided using
  extend."

  [name & opts+sigs]
  (emit-protocol name opts+sigs))

(defn extend 
  "Implementations of protocol methods can be provided using the extend construct:

  (extend ::AType ;or AClass or AnInterface 
    AProtocol
     {:foo an-existing-fn
      :bar (fn [a b] ...)
      :baz (fn ([a]...) ([a b] ...)...)}
    BProtocol 
      {...} 
    ...)
 

  extend takes a type/class (or interface, see below), and one or more
  protocol + method map pairs. It will extend the polymorphism of the
  protocol's methods to call the supplied methods when an AType is
  provided as the first argument. Note that deftype types are specified
  using their keyword tags:

  ::MyType or :my.ns/MyType

  Method maps are maps of the keyword-ized method names to ordinary
  fns. This facilitates easy reuse of existing fns and fn maps, for
  code reuse/mixins without derivation or composition. You can extend
  an interface to a protocol. This is primarily to facilitate interop
  with the host (e.g. Java) but opens the door to incidental multiple
  inheritance of implementation since a class can inherit from more
  than one interface, both of which extend the protocol. It is TBD how
  to specify which impl to use. You can extend a protocol on nil.

  If you are supplying the definitions explicitly (i.e. not reusing
  exsting functions or mixin maps), you may find it more convenient to
  use the extend-type, extend-class or extend-protocol macros.

  Note that multiple independent extend clauses can exist for the same
  type, not all protocols need be defined in a single extend call.

  See also:
  extends?, satisfies?, extenders"

  [atype & proto+mmaps]
  (doseq [[proto mmap] (partition 2 proto+mmaps)]
    (-reset-methods (alter-var-root (:var proto) assoc-in [:impls atype] mmap))))

(defn- parse-impls [specs]
  (loop [ret {} s specs]
    (if (seq s)
      (recur (assoc ret (first s) (take-while seq? (next s)))
             (drop-while seq? (next s)))
      ret)))

(defn- emit-impl [[p fs]]
  [p (zipmap (map #(-> % first keyword) fs)
             (map #(cons 'fn (drop 1 %)) fs))])

(defn- emit-hinted-impl [c [p fs]]
  (let [hint (fn [specs]
               (let [specs (if (vector? (first specs)) 
                                        (list specs) 
                                        specs)]
                 (map (fn [[[target & args] & body]]
                        (cons (apply vector (vary-meta target assoc :tag c) args)
                              body))
                      specs)))]
    [p (zipmap (map #(-> % first keyword) fs)
               (map #(cons 'fn (hint (drop 1 %))) fs))]))

(defn- emit-extend-type [t specs]
  (let [impls (parse-impls specs)]
    `(extend ~t
             ~@(mapcat emit-impl impls))))

(defn- emit-extend-class [c specs]
  (let [impls (parse-impls specs)]
    `(extend ~c
             ~@(mapcat (partial emit-hinted-impl c) impls))))

(defmacro extend-type 
  "A macro that expands into an extend call. Useful when you are
  supplying the definitions explicitly inline, extend-type
  automatically creates the maps required by extend.

  (extend-type ::MyType 
    Countable
      (cnt [c] ...)
    Foo
      (bar [x y] ...)
      (baz ([x] ...) ([x y & zs] ...)))

  expands into:

  (extend ::MyType
   Countable
     {:cnt (fn [c] ...)}
   Foo
     {:baz (fn ([x] ...) ([x y & zs] ...))
      :bar (fn [x y] ...)})"

  [t & specs]
  (emit-extend-type t specs))

(defmacro extend-class 
  "Like extend-type, for the case when the extended type is a
  class. Propagates the class as a type hint on the first argument of
  all fns" 
  [c & specs]
  (emit-extend-class c specs))

(defn- emit-extend-protocol [p specs]
  (let [impls (parse-impls specs)]
    `(do
       ~@(map (fn [[t fs]]
                (if (symbol? t)
                  `(extend-class ~t ~p ~@fs)
                  `(extend-type ~t ~p ~@fs)))
              impls))))

(defmacro extend-protocol 
  "Useful when you want to provide several implementations of the same
  protocol all at once. Takes a single protocol and the implementation
  of that protocol for one or more types. Expands into calls to
  extend-type and extend-class:

  (extend-protocol Protocol
    ::AType
      (foo [x] ...)
      (bar [x y] ...)
    ::BType
      (foo [x] ...)
      (bar [x y] ...)
    AClass
      (foo [x] ...)
      (bar [x y] ...)
    nil
      (foo [x] ...)
      (bar [x y] ...))

  expands into:

  (do
   (clojure.core/extend-type ::AType Protocol 
     (foo [x] ...) 
     (bar [x y] ...))
   (clojure.core/extend-type ::BType Protocol 
     (foo [x] ...) 
     (bar [x y] ...))
   (clojure.core/extend-class AClass Protocol 
     (foo [x] ...) 
     (bar [x y] ...))
   (clojure.core/extend-type nil Protocol 
     (foo [x] ...) 
     (bar [x y] ...)))"

  [p & specs]
  (emit-extend-protocol p specs))