|
Java example source code file (core_deftype.clj)
The core_deftype.clj Java example source code; Copyright (c) Rich Hickey. All rights reserved. ; The use and distribution terms for this software are covered by the ; Eclipse Public License 1.0 (http://opensource.org/licenses/eclipse-1.0.php) ; which can be found in the file epl-v10.html at the root of this distribution. ; By using this software in any fashion, you are agreeing to be bound by ; the terms of this license. ; You must not remove this notice, or any other, from this software. (in-ns 'clojure.core) ;;;;;;;;;;;;;;;;;;;;;;;;;;;; definterface ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; (defn namespace-munge "Convert a Clojure namespace name to a legal Java package name." {:added "1.2"} [ns] (.replace (str ns) \- \_)) ;for now, built on gen-interface (defmacro definterface "Creates a new Java interface with the given name and method sigs. The method return types and parameter types may be specified with type hints, defaulting to Object if omitted. (definterface MyInterface (^int method1 [x]) (^Bar method2 [^Baz b ^Quux q]))" {:added "1.2"} ;; Present since 1.2, but made public in 1.5. [name & sigs] (let [tag (fn [x] (or (:tag (meta x)) Object)) psig (fn [[name [& args]]] (vector name (vec (map tag args)) (tag name) (map meta args))) cname (with-meta (symbol (str (namespace-munge *ns*) "." name)) (meta name))] `(let [] (gen-interface :name ~cname :methods ~(vec (map psig sigs))) (import ~cname)))) ;;;;;;;;;;;;;;;;;;;;;;;;;;;; reify/deftype ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; (defn- parse-opts [s] (loop [opts {} [k v & rs :as s] s] (if (keyword? k) (recur (assoc opts k v) rs) [opts s]))) (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- parse-opts+specs [opts+specs] (let [[opts specs] (parse-opts opts+specs) impls (parse-impls specs) interfaces (-> (map #(if (var? (resolve %)) (:on (deref (resolve %))) %) (keys impls)) set (disj 'Object 'java.lang.Object) vec) methods (map (fn [[name params & body]] (cons name (maybe-destructured params body))) (apply concat (vals impls)))] (when-let [bad-opts (seq (remove #{:no-print :load-ns} (keys opts)))] (throw (IllegalArgumentException. (apply print-str "Unsupported option(s) -" bad-opts)))) [interfaces methods opts])) (defmacro reify "reify is a macro with the following structure: (reify options* specs*) Currently there are no options. Each spec consists of the protocol or interface name followed by zero or more method bodies: protocol-or-interface-or-Object (methodName [args+] body)* Methods should be supplied for all methods of the desired protocol(s) and interface(s). You can also define overrides for methods of Object. Note that the first parameter must be supplied to correspond to the target object ('this' in Java parlance). Thus methods for interfaces will take one more argument than do the interface declarations. Note also that recur calls to the method head should *not* pass the target object, it will be supplied automatically and can not be substituted. The return type can be indicated by a type hint on the method name, and arg types can be indicated by a type hint on arg names. If you leave out all hints, reify will try to match on same name/arity method in the protocol(s)/interface(s) - this is preferred. If you supply any hints at all, no inference is done, so all hints (or default of Object) must be correct, for both arguments and return type. If a method is overloaded in a protocol/interface, multiple independent method definitions must be supplied. If overloaded with same arity in an interface you must specify complete hints to disambiguate - a missing hint implies Object. recur works to method heads The method bodies of reify are lexical closures, and can refer to the surrounding local scope: (str (let [f \"foo\"] (reify Object (toString [this] f)))) == \"foo\" (seq (let [f \"foo\"] (reify clojure.lang.Seqable (seq [this] (seq f))))) == (\\f \\o \\o)) reify always implements clojure.lang.IObj and transfers meta data of the form to the created object. (meta ^{:k :v} (reify Object (toString [this] \"foo\"))) == {:k :v}" {:added "1.2"} [& opts+specs] (let [[interfaces methods] (parse-opts+specs opts+specs)] (with-meta `(reify* ~interfaces ~@methods) (meta &form)))) (defn hash-combine [x y] (clojure.lang.Util/hashCombine x (clojure.lang.Util/hash y))) (defn munge [s] ((if (symbol? s) symbol str) (clojure.lang.Compiler/munge (str s)))) (defn- imap-cons [^IPersistentMap this o] (cond (map-entry? o) (let [^java.util.Map$Entry pair o] (.assoc this (.getKey pair) (.getValue pair))) (instance? clojure.lang.IPersistentVector o) (let [^clojure.lang.IPersistentVector vec o] (.assoc this (.nth vec 0) (.nth vec 1))) :else (loop [this this o o] (if (seq o) (let [^java.util.Map$Entry pair (first o)] (recur (.assoc this (.getKey pair) (.getValue pair)) (rest o))) this)))) (defn- emit-defrecord "Do not use this directly - use defrecord" {:added "1.2"} [tagname cname fields interfaces methods opts] (let [classname (with-meta (symbol (str (namespace-munge *ns*) "." cname)) (meta cname)) interfaces (vec interfaces) interface-set (set (map resolve interfaces)) methodname-set (set (map first methods)) hinted-fields fields fields (vec (map #(with-meta % nil) fields)) base-fields fields fields (conj fields '__meta '__extmap) type-hash (hash classname)] (when (some #{:volatile-mutable :unsynchronized-mutable} (mapcat (comp keys meta) hinted-fields)) (throw (IllegalArgumentException. ":volatile-mutable or :unsynchronized-mutable not supported for record fields"))) (let [gs (gensym)] (letfn [(irecord [[i m]] [(conj i 'clojure.lang.IRecord) m]) (eqhash [[i m]] [(conj i 'clojure.lang.IHashEq) (conj m `(hasheq [this#] (bit-xor ~type-hash (clojure.lang.APersistentMap/mapHasheq this#))) `(hashCode [this#] (clojure.lang.APersistentMap/mapHash this#)) `(equals [this# ~gs] (clojure.lang.APersistentMap/mapEquals this# ~gs)))]) (iobj [[i m]] [(conj i 'clojure.lang.IObj) (conj m `(meta [this#] ~'__meta) `(withMeta [this# ~gs] (new ~tagname ~@(replace {'__meta gs} fields))))]) (ilookup [[i m]] [(conj i 'clojure.lang.ILookup 'clojure.lang.IKeywordLookup) (conj m `(valAt [this# k#] (.valAt this# k# nil)) `(valAt [this# k# else#] (case k# ~@(mapcat (fn [fld] [(keyword fld) fld]) base-fields) (get ~'__extmap k# else#))) `(getLookupThunk [this# k#] (let [~'gclass (class this#)] (case k# ~@(let [hinted-target (with-meta 'gtarget {:tag tagname})] (mapcat (fn [fld] [(keyword fld) `(reify clojure.lang.ILookupThunk (get [~'thunk ~'gtarget] (if (identical? (class ~'gtarget) ~'gclass) (. ~hinted-target ~(symbol (str "-" fld))) ~'thunk)))]) base-fields)) nil))))]) (imap [[i m]] [(conj i 'clojure.lang.IPersistentMap) (conj m `(count [this#] (+ ~(count base-fields) (count ~'__extmap))) `(empty [this#] (throw (UnsupportedOperationException. (str "Can't create empty: " ~(str classname))))) `(cons [this# e#] ((var imap-cons) this# e#)) `(equiv [this# ~gs] (boolean (or (identical? this# ~gs) (when (identical? (class this#) (class ~gs)) (let [~gs ~(with-meta gs {:tag tagname})] (and ~@(map (fn [fld] `(= ~fld (. ~gs ~(symbol (str "-" fld))))) base-fields) (= ~'__extmap (. ~gs ~'__extmap)))))))) `(containsKey [this# k#] (not (identical? this# (.valAt this# k# this#)))) `(entryAt [this# k#] (let [v# (.valAt this# k# this#)] (when-not (identical? this# v#) (clojure.lang.MapEntry/create k# v#)))) `(seq [this#] (seq (concat [~@(map #(list `clojure.lang.MapEntry/create (keyword %) %) base-fields)] ~'__extmap))) `(iterator [~gs] (clojure.lang.RecordIterator. ~gs [~@(map keyword base-fields)] (RT/iter ~'__extmap))) `(assoc [this# k# ~gs] (condp identical? k# ~@(mapcat (fn [fld] [(keyword fld) (list* `new tagname (replace {fld gs} fields))]) base-fields) (new ~tagname ~@(remove #{'__extmap} fields) (assoc ~'__extmap k# ~gs)))) `(without [this# 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#))))))]) (ijavamap [[i m]] [(conj i 'java.util.Map 'java.io.Serializable) (conj m `(size [this#] (.count this#)) `(isEmpty [this#] (= 0 (.count this#))) `(containsValue [this# v#] (boolean (some #{v#} (vals this#)))) `(get [this# k#] (.valAt this# k#)) `(put [this# k# v#] (throw (UnsupportedOperationException.))) `(remove [this# k#] (throw (UnsupportedOperationException.))) `(putAll [this# m#] (throw (UnsupportedOperationException.))) `(clear [this#] (throw (UnsupportedOperationException.))) `(keySet [this#] (set (keys this#))) `(values [this#] (vals this#)) `(entrySet [this#] (set this#)))]) ] (let [[i m] (-> [interfaces methods] irecord eqhash iobj ilookup imap ijavamap)] `(deftype* ~(symbol (name (ns-name *ns*)) (name tagname)) ~classname ~(conj hinted-fields '__meta '__extmap) :implements ~(vec i) ~@(mapcat identity opts) ~@m)))))) (defn- build-positional-factory "Used to build a positional factory for a given type/record. Because of the limitation of 20 arguments to Clojure functions, this factory needs to be constructed to deal with more arguments. It does this by building a straight forward type/record ctor call in the <=20 case, and a call to the same ctor pulling the extra args out of the & overage parameter. Finally, the arity is constrained to the number of expected fields and an ArityException will be thrown at runtime if the actual arg count does not match." [nom classname fields] (let [fn-name (symbol (str '-> nom)) [field-args over] (split-at 20 fields) field-count (count fields) arg-count (count field-args) over-count (count over) docstring (str "Positional factory function for class " classname ".")] `(defn ~fn-name ~docstring [~@field-args ~@(if (seq over) '[& overage] [])] ~(if (seq over) `(if (= (count ~'overage) ~over-count) (new ~classname ~@field-args ~@(for [i (range 0 (count over))] (list `nth 'overage i))) (throw (clojure.lang.ArityException. (+ ~arg-count (count ~'overage)) (name '~fn-name)))) `(new ~classname ~@field-args))))) (defn- validate-fields "" [fields name] (when-not (vector? fields) (throw (AssertionError. "No fields vector given."))) (let [specials #{'__meta '__extmap}] (when (some specials fields) (throw (AssertionError. (str "The names in " specials " cannot be used as field names for types or records."))))) (let [non-syms (remove symbol? fields)] (when (seq non-syms) (throw (clojure.lang.Compiler$CompilerException. *file* (.deref clojure.lang.Compiler/LINE) (.deref clojure.lang.Compiler/COLUMN) (AssertionError. (str "defrecord and deftype fields must be symbols, " *ns* "." name " had: " (apply str (interpose ", " non-syms))))))))) (defmacro defrecord "(defrecord name [fields*] options* specs*) Options are expressed as sequential keywords and arguments (in any order). Supported options: :load-ns - if true, importing the record class will cause the namespace in which the record was defined to be loaded. Defaults to false. Each spec consists of a protocol or interface name followed by zero or more method bodies: protocol-or-interface-or-Object (methodName [args*] body)* Dynamically generates compiled bytecode for class with the given name, in a package with the same name as the current namespace, the given fields, and, optionally, methods for protocols and/or interfaces. The class will have the (immutable) fields named by fields, which can have type hints. Protocols/interfaces and methods are optional. The only methods that can be supplied are those declared in the protocols/interfaces. Note that method bodies are not closures, the local environment includes only the named fields, and those fields can be accessed directly. Method definitions take the form: (methodname [args*] body) 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. Methods should be supplied for all methods of the desired protocol(s) and interface(s). You can also define overrides for methods of Object. Note that a parameter must be supplied to correspond to the target object ('this' in Java parlance). Thus methods for interfaces will take one more argument than do the interface declarations. Note also that recur calls to the method head should *not* pass the target object, it will be supplied automatically and can not be substituted. 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 several (clojure.lang) interfaces generated automatically: IObj (metadata support) and IPersistentMap, and all of their superinterfaces. In addition, defrecord will define type-and-value-based =, and will defined Java .hashCode and .equals consistent with the contract for java.util.Map. 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. 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). Note that the field names __meta and __extmap are currently reserved and should not be used when defining your own records. Given (defrecord TypeName ...), two factory functions will be defined: ->TypeName, taking positional parameters for the fields, and map->TypeName, taking a map of keywords to field values." {:added "1.2" :arglists '([name [& fields] & opts+specs])} [name fields & opts+specs] (validate-fields fields name) (let [gname name [interfaces methods opts] (parse-opts+specs opts+specs) ns-part (namespace-munge *ns*) classname (symbol (str ns-part "." gname)) hinted-fields fields fields (vec (map #(with-meta % nil) fields))] `(let [] (declare ~(symbol (str '-> gname))) (declare ~(symbol (str 'map-> gname))) ~(emit-defrecord name gname (vec hinted-fields) (vec interfaces) methods opts) (import ~classname) ~(build-positional-factory gname classname fields) (defn ~(symbol (str 'map-> gname)) ~(str "Factory function for class " classname ", taking a map of keywords to field values.") ([m#] (~(symbol (str classname "/create")) (if (instance? clojure.lang.MapEquivalence m#) m# (into {} m#))))) ~classname))) (defn record? "Returns true if x is a record" {:added "1.6" :static true} [x] (instance? clojure.lang.IRecord x)) (defn- emit-deftype* "Do not use this directly - use deftype" [tagname cname fields interfaces methods opts] (let [classname (with-meta (symbol (str (namespace-munge *ns*) "." cname)) (meta cname)) interfaces (conj interfaces 'clojure.lang.IType)] `(deftype* ~(symbol (name (ns-name *ns*)) (name tagname)) ~classname ~fields :implements ~interfaces ~@(mapcat identity opts) ~@methods))) (defmacro deftype "(deftype name [fields*] options* specs*) Options are expressed as sequential keywords and arguments (in any order). Supported options: :load-ns - if true, importing the record class will cause the namespace in which the record was defined to be loaded. Defaults to false. Each spec consists of a protocol or interface name followed by zero or more method bodies: protocol-or-interface-or-Object (methodName [args*] body)* Dynamically generates compiled bytecode for class with the given name, in a package with the same name as the current namespace, the given fields, and, optionally, methods for protocols and/or interfaces. The class will have the (by default, immutable) fields named by fields, which can have type hints. Protocols/interfaces and methods are optional. The only methods that can be supplied are those declared in the protocols/interfaces. Note that method bodies are not closures, the local environment includes only the named fields, and those fields can be accessed directly. Fields can be qualified with the metadata :volatile-mutable true or :unsynchronized-mutable true, at which point (set! afield aval) will be supported in method bodies. Note well that mutable fields are extremely difficult to use correctly, and are present only to facilitate the building of higher level constructs, such as Clojure's reference types, in Clojure itself. They are for experts only - if the semantics and implications of :volatile-mutable or :unsynchronized-mutable are not immediately apparent to you, you should not be using them. Method definitions take the form: (methodname [args*] body) 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. Methods should be supplied for all methods of the desired protocol(s) and interface(s). You can also define overrides for methods of Object. Note that a parameter must be supplied to correspond to the target object ('this' in Java parlance). Thus methods for interfaces will take one more argument than do the interface declarations. Note also that recur calls to the method head should *not* pass the target object, it will be supplied automatically and can not be substituted. In the method bodies, the (unqualified) name can be used to name the class (for calls to new, instance? etc). 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. One constructor will be defined, taking the designated fields. Note that the field names __meta and __extmap are currently reserved and should not be used when defining your own types. Given (deftype TypeName ...), a factory function called ->TypeName will be defined, taking positional parameters for the fields" {:added "1.2" :arglists '([name [& fields] & opts+specs])} [name fields & opts+specs] (validate-fields fields name) (let [gname name [interfaces methods opts] (parse-opts+specs opts+specs) ns-part (namespace-munge *ns*) classname (symbol (str ns-part "." gname)) hinted-fields fields fields (vec (map #(with-meta % nil) fields)) [field-args over] (split-at 20 fields)] `(let [] ~(emit-deftype* name gname (vec hinted-fields) (vec interfaces) methods opts) (import ~classname) ~(build-positional-factory gname classname fields) ~classname))) ;;;;;;;;;;;;;;;;;;;;;;; protocols ;;;;;;;;;;;;;;;;;;;;;;;; (defn- expand-method-impl-cache [^clojure.lang.MethodImplCache cache c f] (if (.map cache) (let [cs (assoc (.map cache) c (clojure.lang.MethodImplCache$Entry. c f))] (clojure.lang.MethodImplCache. (.protocol cache) (.methodk cache) cs)) (let [cs (into1 {} (remove (fn [[c e]] (nil? e)) (map vec (partition 2 (.table cache))))) cs (assoc cs c (clojure.lang.MethodImplCache$Entry. c f))] (if-let [[shift mask] (maybe-min-hash (map hash (keys cs)))] (let [table (make-array Object (* 2 (inc mask))) table (reduce1 (fn [^objects t [c e]] (let [i (* 2 (int (shift-mask shift mask (hash c))))] (aset t i c) (aset t (inc i) e) t)) table cs)] (clojure.lang.MethodImplCache. (.protocol cache) (.methodk cache) shift mask table)) (clojure.lang.MethodImplCache. (.protocol cache) (.methodk cache) cs))))) (defn- super-chain [^Class c] (when c (cons c (super-chain (.getSuperclass c))))) (defn- pref ([] nil) ([a] a) ([^Class a ^Class b] (if (.isAssignableFrom a b) b a))) (defn find-protocol-impl [protocol x] (if (instance? (:on-interface protocol) x) x (let [c (class x) impl #(get (:impls protocol) %)] (or (impl c) (and c (or (first (remove nil? (map impl (butlast (super-chain c))))) (when-let [t (reduce1 pref (filter impl (disj (supers c) Object)))] (impl t)) (impl Object))))))) (defn find-protocol-method [protocol methodk x] (get (find-protocol-impl protocol x) methodk)) (defn- protocol? [maybe-p] (boolean (:on-interface maybe-p))) (defn- implements? [protocol atype] (and atype (.isAssignableFrom ^Class (:on-interface protocol) atype))) (defn extends? "Returns true if atype extends protocol" {:added "1.2"} [protocol atype] (boolean (or (implements? protocol atype) (get (:impls protocol) atype)))) (defn extenders "Returns a collection of the types explicitly extending protocol" {:added "1.2"} [protocol] (keys (:impls protocol))) (defn satisfies? "Returns true if x satisfies the protocol" {:added "1.2"} [protocol x] (boolean (find-protocol-impl protocol x))) (defn -cache-protocol-fn [^clojure.lang.AFunction pf x ^Class c ^clojure.lang.IFn interf] (let [cache (.__methodImplCache pf) f (if (.isInstance c x) interf (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}) ginterf (gensym)] `(fn [cache#] (let [~ginterf (fn ~@(map (fn [args] (let [gargs (map #(gensym (str "gf__" % "__")) args) target (first gargs)] `([~@gargs] (. ~(with-meta target {:tag on-interface}) (~(or on-method method) ~@(rest gargs)))))) arglists)) ^clojure.lang.AFunction f# (fn ~gthis ~@(map (fn [args] (let [gargs (map #(gensym (str "gf__" % "__")) args) target (first gargs)] `([~@gargs] (let [cache# (.__methodImplCache ~gthis) f# (.fnFor cache# (clojure.lang.Util/classOf ~target))] (if f# (f# ~@gargs) ((-cache-protocol-fn ~gthis ~target ~on-interface ~ginterf) ~@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 (and v (bound? v) (not= 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 [iname (symbol (str (munge (namespace-munge *ns*)) "." (munge name))) [opts sigs] (loop [opts {:on (list 'quote iname) :on-interface iname} 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 (when sigs (reduce1 (fn [m s] (let [name-meta (meta (first s)) mname (with-meta (first s) nil) [arglists doc] (loop [as [] rs (rest s)] (if (vector? (first rs)) (recur (conj as (first rs)) (next rs)) [(seq as) (first rs)]))] (when (some #{0} (map count arglists)) (throw (IllegalArgumentException. (str "Definition of function " mname " in protocol " name " must take at least one arg.")))) (when (m (keyword mname)) (throw (IllegalArgumentException. (str "Function " mname " in protocol " name " was redefined. Specify all arities in single definition.")))) (assoc m (keyword mname) (merge name-meta {:name (vary-meta mname assoc :doc doc :arglists arglists) :arglists arglists :doc doc})))) {} sigs)) meths (mapcat (fn [sig] (let [m (munge (:name sig))] (map #(vector m (vec (repeat (dec (count %))'Object)) 'Object) (:arglists sig)))) (vals sigs))] `(do (defonce ~name {}) (gen-interface :name ~iname :methods ~meths) (alter-meta! (var ~name) assoc :doc ~(:doc opts)) ~(when sigs `(#'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) (merge '~s {:protocol (var ~name)}))) (emit-method-builder (:on-interface 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 [this a b] \"bar docs\") (baz [this a] [this a b] [this 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, which is required and corresponds to the implicit target object ('this' in Java parlance). 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. defprotocol will automatically generate a corresponding interface, with the same name as the protocol, i.e. given a protocol: my.ns/Protocol, an interface: my.ns.Protocol. The interface will have methods corresponding to the protocol functions, and the protocol will automatically work with instances of the interface. Note that you should not use this interface with deftype or reify, as they support the protocol directly: (defprotocol P (foo [this]) (bar-me [this] [this y])) (deftype Foo [a b c] P (foo [this] a) (bar-me [this] b) (bar-me [this y] (+ c y))) (bar-me (Foo. 1 2 3) 42) => 45 (foo (let [x 42] (reify P (foo [this] 17) (bar-me [this] x) (bar-me [this y] x)))) => 17" {:added "1.2"} [name & opts+sigs] (emit-protocol name opts+sigs)) (defn extend "Implementations of protocol methods can be provided using the extend construct: (extend AType 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. 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 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" {:added "1.2"} [atype & proto+mmaps] (doseq [[proto mmap] (partition 2 proto+mmaps)] (when-not (protocol? proto) (throw (IllegalArgumentException. (str proto " is not a protocol")))) (when (implements? proto atype) (throw (IllegalArgumentException. (str atype " already directly implements " (:on-interface proto) " for protocol:" (:var proto))))) (-reset-methods (alter-var-root (:var proto) assoc-in [:impls atype] mmap)))) (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 name keyword) fs) (map #(cons `fn (hint (drop 1 %))) fs))])) (defn- emit-extend-type [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. Propagates the class as a type hint on the first argument of all fns. (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] ...)})" {:added "1.2"} [t & specs] (emit-extend-type t specs)) (defn- emit-extend-protocol [p specs] (let [impls (parse-impls specs)] `(do ~@(map (fn [[t 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: (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-type AClass Protocol (foo [x] ...) (bar [x y] ...)) (clojure.core/extend-type nil Protocol (foo [x] ...) (bar [x y] ...)))" {:added "1.2"} [p & specs] (emit-extend-protocol p specs)) Other Java examples (source code examples)Here is a short list of links related to this Java core_deftype.clj source code file: |
... this post is sponsored by my books ... | |
#1 New Release! |
FP Best Seller |
Copyright 1998-2021 Alvin Alexander, alvinalexander.com
All Rights Reserved.
A percentage of advertising revenue from
pages under the /java/jwarehouse
URI on this website is
paid back to open source projects.