defrecord is one of my favorite examples of the usefulness of macros in Clojure. This particular use demonstrates adding some mild syntax and generating a lot of boiler plate. Let's see what all it does.

replsession.clj

4837 ◯  lein new macrofun
Generating a project called macrofun based on the 'default' template.
To see other templates (app, lein plugin, etc), try `lein help new`.
hobiecat ओम् /tmp:
4838 ◯  cd macrofun 
hobiecat ओम् /tmp/macrofun:
4839 ◯  lein repl
nREPL server started on port 48544
REPL-y 0.1.0-beta10
Clojure 1.4.0
    Exit: Control+D or (exit) or (quit)
Commands: (user/help)
    Docs: (doc function-name-here)
          (find-doc "part-of-name-here")
  Source: (source function-name-here)
          (user/sourcery function-name-here)
 Javadoc: (javadoc java-object-or-class-here)
Examples from clojuredocs.org: [clojuredocs or cdoc]
          (user/clojuredocs name-here)
          (user/clojuredocs "ns-here" "name-here")
user=> (pprint (macroexpand-1 '(defrecord Person [name email address phone])))
(clojure.core/let
 []
 (clojure.core/declare ->Person)
 (clojure.core/declare map->Person)
 (deftype*
  Person
  user.Person
  [name email address phone __meta __extmap]
  :implements
  [clojure.lang.IRecord
   clojure.lang.IObj
   clojure.lang.ILookup
   clojure.lang.IKeywordLookup
   clojure.lang.IPersistentMap
   java.util.Map
   java.io.Serializable]
  (clojure.core/entrySet
   [this__5608__auto__]
   (clojure.core/set this__5608__auto__))
  (clojure.core/values
   [this__5607__auto__]
   (clojure.core/vals this__5607__auto__))
  (clojure.core/keySet
   [this__5606__auto__]
   (clojure.core/set (clojure.core/keys this__5606__auto__)))
  (clojure.core/clear
   [this__5605__auto__]
   (throw (java.lang.UnsupportedOperationException.)))
  (clojure.core/putAll
   [this__5603__auto__ m__5604__auto__]
   (throw (java.lang.UnsupportedOperationException.)))
  (clojure.core/remove
   [this__5601__auto__ k__5602__auto__]
   (throw (java.lang.UnsupportedOperationException.)))
  (clojure.core/put
   [this__5598__auto__ k__5599__auto__ v__5600__auto__]
   (throw (java.lang.UnsupportedOperationException.)))
  (clojure.core/get
   [this__5596__auto__ k__5597__auto__]
   (.valAt this__5596__auto__ k__5597__auto__))
  (clojure.core/containsValue
   [this__5594__auto__ v__5595__auto__]
   (clojure.core/boolean
    (clojure.core/some
     #{v__5595__auto__}
     (clojure.core/vals this__5594__auto__))))
  (clojure.core/isEmpty
   [this__5593__auto__]
   (clojure.core/= 0 (.count this__5593__auto__)))
  (clojure.core/size [this__5592__auto__] (.count this__5592__auto__))
  (clojure.core/without
   [this__5590__auto__ k__5591__auto__]
   (if
    (clojure.core/contains?
     #{:name :phone :email :address}
     k__5591__auto__)
    (clojure.core/dissoc
     (clojure.core/with-meta
      (clojure.core/into {} this__5590__auto__)
      __meta)
     k__5591__auto__)
    (new
     Person
     name
     email
     address
     phone
     __meta
     (clojure.core/not-empty
      (clojure.core/dissoc __extmap k__5591__auto__)))))
  (clojure.core/assoc
   [this__5588__auto__ k__5589__auto__ G__948]
   (clojure.core/condp
    clojure.core/identical?
    k__5589__auto__
    :name
    (new Person G__948 email address phone __meta __extmap)
    :email
    (new Person name G__948 address phone __meta __extmap)
    :address
    (new Person name email G__948 phone __meta __extmap)
    :phone
    (new Person name email address G__948 __meta __extmap)
    (new
     Person
     name
     email
     address
     phone
     __meta
     (clojure.core/assoc __extmap k__5589__auto__ G__948))))
  (clojure.core/iterator
   [this__5587__auto__]
   (clojure.lang.SeqIterator. (.seq this__5587__auto__)))
  (clojure.core/seq
   [this__5586__auto__]
   (clojure.core/seq
    (clojure.core/concat
     [(new clojure.lang.MapEntry :name name)
      (new clojure.lang.MapEntry :email email)
      (new clojure.lang.MapEntry :address address)
      (new clojure.lang.MapEntry :phone phone)]
     __extmap)))
  (clojure.core/entryAt
   [this__5582__auto__ k__5583__auto__]
   (clojure.core/let
    [v__5584__auto__
     (.valAt this__5582__auto__ k__5583__auto__ this__5582__auto__)]
    (clojure.core/when-not
     (clojure.core/identical? this__5582__auto__ v__5584__auto__)
     (clojure.lang.MapEntry. k__5583__auto__ v__5584__auto__))))
  (clojure.core/containsKey
   [this__5580__auto__ k__5581__auto__]
   (clojure.core/not
    (clojure.core/identical?
     this__5580__auto__
     (.valAt this__5580__auto__ k__5581__auto__ this__5580__auto__))))
  (clojure.core/equiv
   [this__5579__auto__ G__948]
   (clojure.core/boolean
    (clojure.core/or
     (clojure.core/identical? this__5579__auto__ G__948)
     (clojure.core/when
      (clojure.core/identical?
       (clojure.core/class this__5579__auto__)
       (clojure.core/class G__948))
      (clojure.core/let
       [G__948 G__948]
       (clojure.core/and
        (clojure.core/= name (. G__948 -name))
        (clojure.core/= email (. G__948 -email))
        (clojure.core/= address (. G__948 -address))
        (clojure.core/= phone (. G__948 -phone))
        (clojure.core/= __extmap (. G__948 __extmap))))))))
  (clojure.core/cons
   [this__5577__auto__ e__5578__auto__]
   (#'clojure.core/imap-cons this__5577__auto__ e__5578__auto__))
  (clojure.core/empty
   [this__5576__auto__]
   (throw
    (java.lang.UnsupportedOperationException.
     (clojure.core/str "Can't create empty: " "user.Person"))))
  (clojure.core/count
   [this__5575__auto__]
   (clojure.core/+ 4 (clojure.core/count __extmap)))
  (clojure.core/getLookupThunk
   [this__5573__auto__ k__5574__auto__]
   (clojure.core/let
    [gclass (clojure.core/class this__5573__auto__)]
    (clojure.core/case
     k__5574__auto__
     :name
     (clojure.core/reify
      clojure.lang.ILookupThunk
      (clojure.core/get
       [thunk gtarget]
       (if
        (clojure.core/identical? (clojure.core/class gtarget) gclass)
        (. gtarget -name)
        thunk)))
     :email
     (clojure.core/reify
      clojure.lang.ILookupThunk
      (clojure.core/get
       [thunk gtarget]
       (if
        (clojure.core/identical? (clojure.core/class gtarget) gclass)
        (. gtarget -email)
        thunk)))
     :address
     (clojure.core/reify
      clojure.lang.ILookupThunk
      (clojure.core/get
       [thunk gtarget]
       (if
        (clojure.core/identical? (clojure.core/class gtarget) gclass)
        (. gtarget -address)
        thunk)))
     :phone
     (clojure.core/reify
      clojure.lang.ILookupThunk
      (clojure.core/get
       [thunk gtarget]
       (if
        (clojure.core/identical? (clojure.core/class gtarget) gclass)
        (. gtarget -phone)
        thunk)))
     nil)))
  (clojure.core/valAt
   [this__5570__auto__ k__5571__auto__ else__5572__auto__]
   (clojure.core/case
    k__5571__auto__
    :name
    name
    :email
    email
    :address
    address
    :phone
    phone
    (clojure.core/get __extmap k__5571__auto__ else__5572__auto__)))
  (clojure.core/valAt
   [this__5568__auto__ k__5569__auto__]
   (.valAt this__5568__auto__ k__5569__auto__ nil))
  (clojure.core/withMeta
   [this__5567__auto__ G__948]
   (new Person name email address phone G__948 __extmap))
  (clojure.core/meta [this__5566__auto__] __meta)
  (clojure.core/equals
   [this__5565__auto__ G__948]
   (clojure.lang.APersistentMap/mapEquals this__5565__auto__ G__948))
  (clojure.core/hashCode
   [this__5564__auto__]
   (clojure.lang.APersistentMap/mapHash this__5564__auto__)))
 (clojure.core/import user.Person)
 (clojure.core/defn
  ->Person
  "Positional factory function for class user.Person."
  [name email address phone]
  (new user.Person name email address phone))
 (clojure.core/defn
  map->Person
  "Factory function for class user.Person, taking a map of keywords to field values."
  ([m__5665__auto__] (user.Person/create m__5665__auto__)))
 user.Person)
nil
user=> (doc defrecord)
-------------------------
clojure.core/defrecord
([name [& fields] & opts+specs])
Macro
  Alpha - subject to change
  
  (defrecord name [fields*]  options* specs*)
  
  Currently there are no options.

  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 directy.

  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.
nil
user=> (doc deftype)
-------------------------
clojure.core/deftype
([name [& fields] & opts+specs])
Macro
  Alpha - subject to change
  
  (deftype name [fields*]  options* specs*)
  
  Currently there are no options.

  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 directy. 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
nil
user=> (comment "Ok...let's expand it all out.")
nil
user=> (pprint (macroexpand '(defrecord Person [name email address phone])))
(let*
 []
 (clojure.core/declare ->Person)
 (clojure.core/declare map->Person)
 (deftype*
  Person
  user.Person
  [name email address phone __meta __extmap]
  :implements
  [clojure.lang.IRecord
   clojure.lang.IObj
   clojure.lang.ILookup
   clojure.lang.IKeywordLookup
   clojure.lang.IPersistentMap
   java.util.Map
   java.io.Serializable]
  (clojure.core/entrySet
   [this__5608__auto__]
   (clojure.core/set this__5608__auto__))
  (clojure.core/values
   [this__5607__auto__]
   (clojure.core/vals this__5607__auto__))
  (clojure.core/keySet
   [this__5606__auto__]
   (clojure.core/set (clojure.core/keys this__5606__auto__)))
  (clojure.core/clear
   [this__5605__auto__]
   (throw (java.lang.UnsupportedOperationException.)))
  (clojure.core/putAll
   [this__5603__auto__ m__5604__auto__]
   (throw (java.lang.UnsupportedOperationException.)))
  (clojure.core/remove
   [this__5601__auto__ k__5602__auto__]
   (throw (java.lang.UnsupportedOperationException.)))
  (clojure.core/put
   [this__5598__auto__ k__5599__auto__ v__5600__auto__]
   (throw (java.lang.UnsupportedOperationException.)))
  (clojure.core/get
   [this__5596__auto__ k__5597__auto__]
   (.valAt this__5596__auto__ k__5597__auto__))
  (clojure.core/containsValue
   [this__5594__auto__ v__5595__auto__]
   (clojure.core/boolean
    (clojure.core/some
     #{v__5595__auto__}
     (clojure.core/vals this__5594__auto__))))
  (clojure.core/isEmpty
   [this__5593__auto__]
   (clojure.core/= 0 (.count this__5593__auto__)))
  (clojure.core/size [this__5592__auto__] (.count this__5592__auto__))
  (clojure.core/without
   [this__5590__auto__ k__5591__auto__]
   (if
    (clojure.core/contains?
     #{:name :phone :email :address}
     k__5591__auto__)
    (clojure.core/dissoc
     (clojure.core/with-meta
      (clojure.core/into {} this__5590__auto__)
      __meta)
     k__5591__auto__)
    (new
     Person
     name
     email
     address
     phone
     __meta
     (clojure.core/not-empty
      (clojure.core/dissoc __extmap k__5591__auto__)))))
  (clojure.core/assoc
   [this__5588__auto__ k__5589__auto__ G__955]
   (clojure.core/condp
    clojure.core/identical?
    k__5589__auto__
    :name
    (new Person G__955 email address phone __meta __extmap)
    :email
    (new Person name G__955 address phone __meta __extmap)
    :address
    (new Person name email G__955 phone __meta __extmap)
    :phone
    (new Person name email address G__955 __meta __extmap)
    (new
     Person
     name
     email
     address
     phone
     __meta
     (clojure.core/assoc __extmap k__5589__auto__ G__955))))
  (clojure.core/iterator
   [this__5587__auto__]
   (clojure.lang.SeqIterator. (.seq this__5587__auto__)))
  (clojure.core/seq
   [this__5586__auto__]
   (clojure.core/seq
    (clojure.core/concat
     [(new clojure.lang.MapEntry :name name)
      (new clojure.lang.MapEntry :email email)
      (new clojure.lang.MapEntry :address address)
      (new clojure.lang.MapEntry :phone phone)]
     __extmap)))
  (clojure.core/entryAt
   [this__5582__auto__ k__5583__auto__]
   (clojure.core/let
    [v__5584__auto__
     (.valAt this__5582__auto__ k__5583__auto__ this__5582__auto__)]
    (clojure.core/when-not
     (clojure.core/identical? this__5582__auto__ v__5584__auto__)
     (clojure.lang.MapEntry. k__5583__auto__ v__5584__auto__))))
  (clojure.core/containsKey
   [this__5580__auto__ k__5581__auto__]
   (clojure.core/not
    (clojure.core/identical?
     this__5580__auto__
     (.valAt this__5580__auto__ k__5581__auto__ this__5580__auto__))))
  (clojure.core/equiv
   [this__5579__auto__ G__955]
   (clojure.core/boolean
    (clojure.core/or
     (clojure.core/identical? this__5579__auto__ G__955)
     (clojure.core/when
      (clojure.core/identical?
       (clojure.core/class this__5579__auto__)
       (clojure.core/class G__955))
      (clojure.core/let
       [G__955 G__955]
       (clojure.core/and
        (clojure.core/= name (. G__955 -name))
        (clojure.core/= email (. G__955 -email))
        (clojure.core/= address (. G__955 -address))
        (clojure.core/= phone (. G__955 -phone))
        (clojure.core/= __extmap (. G__955 __extmap))))))))
  (clojure.core/cons
   [this__5577__auto__ e__5578__auto__]
   (#'clojure.core/imap-cons this__5577__auto__ e__5578__auto__))
  (clojure.core/empty
   [this__5576__auto__]
   (throw
    (java.lang.UnsupportedOperationException.
     (clojure.core/str "Can't create empty: " "user.Person"))))
  (clojure.core/count
   [this__5575__auto__]
   (clojure.core/+ 4 (clojure.core/count __extmap)))
  (clojure.core/getLookupThunk
   [this__5573__auto__ k__5574__auto__]
   (clojure.core/let
    [gclass (clojure.core/class this__5573__auto__)]
    (clojure.core/case
     k__5574__auto__
     :name
     (clojure.core/reify
      clojure.lang.ILookupThunk
      (clojure.core/get
       [thunk gtarget]
       (if
        (clojure.core/identical? (clojure.core/class gtarget) gclass)
        (. gtarget -name)
        thunk)))
     :email
     (clojure.core/reify
      clojure.lang.ILookupThunk
      (clojure.core/get
       [thunk gtarget]
       (if
        (clojure.core/identical? (clojure.core/class gtarget) gclass)
        (. gtarget -email)
        thunk)))
     :address
     (clojure.core/reify
      clojure.lang.ILookupThunk
      (clojure.core/get
       [thunk gtarget]
       (if
        (clojure.core/identical? (clojure.core/class gtarget) gclass)
        (. gtarget -address)
        thunk)))
     :phone
     (clojure.core/reify
      clojure.lang.ILookupThunk
      (clojure.core/get
       [thunk gtarget]
       (if
        (clojure.core/identical? (clojure.core/class gtarget) gclass)
        (. gtarget -phone)
        thunk)))
     nil)))
  (clojure.core/valAt
   [this__5570__auto__ k__5571__auto__ else__5572__auto__]
   (clojure.core/case
    k__5571__auto__
    :name
    name
    :email
    email
    :address
    address
    :phone
    phone
    (clojure.core/get __extmap k__5571__auto__ else__5572__auto__)))
  (clojure.core/valAt
   [this__5568__auto__ k__5569__auto__]
   (.valAt this__5568__auto__ k__5569__auto__ nil))
  (clojure.core/withMeta
   [this__5567__auto__ G__955]
   (new Person name email address phone G__955 __extmap))
  (clojure.core/meta [this__5566__auto__] __meta)
  (clojure.core/equals
   [this__5565__auto__ G__955]
   (clojure.lang.APersistentMap/mapEquals this__5565__auto__ G__955))
  (clojure.core/hashCode
   [this__5564__auto__]
   (clojure.lang.APersistentMap/mapHash this__5564__auto__)))
 (clojure.core/import user.Person)
 (clojure.core/defn
  ->Person
  "Positional factory function for class user.Person."
  [name email address phone]
  (new user.Person name email address phone))
 (clojure.core/defn
  map->Person
  "Factory function for class user.Person, taking a map of keywords to field values."
  ([m__5665__auto__] (user.Person/create m__5665__auto__)))
 user.Person)
nil
user=>