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<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE erlref SYSTEM "erlref.dtd">
<erlref>
<header>
    <copyright>
      <year>2007</year><year>2013</year>
      <holder>Ericsson AB. All Rights Reserved.</holder>
    </copyright>
    <legalnotice>
      The contents of this file are subject to the Erlang Public License,
      Version 1.1, (the "License"); you may not use this file except in
      compliance with the License. You should have received a copy of the
      Erlang Public License along with this software. If not, it can be
      retrieved online at http://www.erlang.org/.
    
      Software distributed under the License is distributed on an "AS IS"
      basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
      the License for the specific language governing rights and limitations
      under the License.
    
    </legalnotice>

<title>array</title>
<prepared></prepared>
<responsible></responsible>
<docno>1</docno>
<approved></approved>
<checked></checked>
<date></date>
<rev>A</rev>
<file>array.xml</file></header>
<module>array</module>
<modulesummary>Functional, extendible arrays.</modulesummary>
<description>
<p>Functional, extendible arrays. Arrays can have fixed size, or  
can grow automatically as needed. A default value is used for entries  
that have not been explicitly set.</p>
 
  <p>Arrays uses <em>zero</em> based indexing. This is a deliberate design  
choice and differs from other erlang datastructures, e.g. tuples.</p>
 
  <p>Unless specified by the user when the array is created, the default
  value is the atom <c>undefined</c>. There is no difference between an
  unset entry and an entry which has been explicitly set to the same
  value as the default one (cf. <seealso marker="#reset-2">reset/2</seealso>). If you need to  
differentiate between unset and set entries, you must make sure that  
the default value cannot be confused with the values of set entries.</p>
 
  <p>The array never shrinks automatically; if an index <c>I</c> has been used
  successfully to set an entry, all indices in the range [0,<c>I</c>] will
  stay accessible unless the array size is explicitly changed by
  calling <seealso marker="#resize-2">resize/2</seealso>.</p>
 
  <p>Examples:
  </p><pre>  %% Create a fixed-size array with entries 0-9 set to 'undefined'
  A0 = array:new(10).
  10 = array:size(A0).
 
  %% Create an extendible array and set entry 17 to 'true',
  %% causing the array to grow automatically
  A1 = array:set(17, true, array:new()).
  18 = array:size(A1).
 
  %% Read back a stored value
  true = array:get(17, A1).
 
  %% Accessing an unset entry returns the default value
  undefined = array:get(3, A1).
 
  %% Accessing an entry beyond the last set entry also returns the
  %% default value, if the array does not have fixed size
  undefined = array:get(18, A1).
 
  %% "sparse" functions ignore default-valued entries
  A2 = array:set(4, false, A1).
  [{4, false}, {17, true}] = array:sparse_to_orddict(A2).
 
  %% An extendible array can be made fixed-size later
  A3 = array:fix(A2).
 
  %% A fixed-size array does not grow automatically and does not
  %% allow accesses beyond the last set entry
  {'EXIT',{badarg,_}} = (catch array:set(18, true, A3)).
  {'EXIT',{badarg,_}} = (catch array:get(18, A3)).</pre></description>
<datatypes>
  <datatype>
    <name><marker id="type-array">array()</marker></name>
    <desc>
      <p>A functional, extendible array. The representation is
        not documented and is subject to change without notice. Note that
        arrays cannot be directly compared for equality.</p>
    </desc>
  </datatype>
  <datatype>
    <name name="array_indx"/>
  </datatype>
  <datatype>
    <name name="array_opts"/>
  </datatype>
  <datatype>
    <name name="array_opt"/>
  </datatype>
  <datatype>
    <name name="indx_pairs"/>
  </datatype>
  <datatype>
    <name name="indx_pair"/>
  </datatype>
</datatypes>

<funcs>
<func>
<name name="default" arity="1"/>
<fsummary>Get the value used for uninitialized entries.</fsummary>

<desc><marker id="default-1"/>

<p>Get the value used for uninitialized entries.
 </p>
<p><em>See also:</em> <seealso marker="#new-2">new/2</seealso>.</p>
</desc></func>
<func>
<name name="fix" arity="1"/>
<fsummary>Fix the size of the array.</fsummary>

<desc><marker id="fix-1"/>

<p>Fix the size of the array. This prevents it from growing
  automatically upon insertion; see also <seealso marker="#set-3">set/3</seealso>.</p>
<p><em>See also:</em> <seealso marker="#relax-1">relax/1</seealso>.</p>
</desc></func>
<func>
<name name="foldl" arity="3"/>
<fsummary>Fold the elements of the array using the given function and
  initial accumulator value.</fsummary>
<desc><marker id="foldl-3"/>
<p>Fold the elements of the array using the given function and
  initial accumulator value. The elements are visited in order from the
  lowest index to the highest. If <c><anno>Function</anno></c> is not a function, the
  call fails with reason <c>badarg</c>.
 </p>
<p><em>See also:</em> <seealso marker="#foldr-3">foldr/3</seealso>, <seealso marker="#map-2">map/2</seealso>, <seealso marker="#sparse_foldl-3">sparse_foldl/3</seealso>.</p>
</desc></func>
<func>
<name name="foldr" arity="3"/>
<fsummary>Fold the elements of the array right-to-left using the given
  function and initial accumulator value.</fsummary>
<desc><marker id="foldr-3"/>

<p>Fold the elements of the array right-to-left using the given
  function and initial accumulator value. The elements are visited in
  order from the highest index to the lowest. If <c><anno>Function</anno></c> is not a
  function, the call fails with reason <c>badarg</c>.
 </p>
<p><em>See also:</em> <seealso marker="#foldl-3">foldl/3</seealso>, <seealso marker="#map-2">map/2</seealso>.</p>
</desc></func>
<func>
<name name="from_list" arity="1"/>
<fsummary>Equivalent to from_list(List, undefined).
</fsummary>

<desc><marker id="from_list-1"/>
<p>Equivalent to <seealso marker="#from_list-2">from_list(<anno>List</anno>, undefined)</seealso>.</p>
</desc></func>
<func>
<name name="from_list" arity="2"/>
<fsummary>Convert a list to an extendible array.</fsummary>

<desc><marker id="from_list-2"/>

<p>Convert a list to an extendible array. <c><anno>Default</anno></c> is used as the value
  for uninitialized entries of the array. If <c><anno>List</anno></c> is not a proper list,
  the call fails with reason <c>badarg</c>.
 </p>
<p><em>See also:</em> <seealso marker="#new-2">new/2</seealso>, <seealso marker="#to_list-1">to_list/1</seealso>.</p>
</desc></func>
<func>
<name name="from_orddict" arity="1"/>
<fsummary>Equivalent to from_orddict(Orddict, undefined).
</fsummary>

<desc><marker id="from_orddict-1"/>
<p>Equivalent to <seealso marker="#from_orddict-2">from_orddict(<anno>Orddict</anno>, undefined)</seealso>.</p>
</desc></func>
<func>
<name name="from_orddict" arity="2"/>
<fsummary>Convert an ordered list of pairs {Index, Value} to a
  corresponding extendible array.</fsummary>

<desc><marker id="from_orddict-2"/>

<p>Convert an ordered list of pairs <c>{Index, Value}</c> to a
  corresponding extendible array. <c><anno>Default</anno></c> is used as the value for
  uninitialized entries of the array. If <c><anno>Orddict</anno></c> is not a proper,
  ordered list of pairs whose first elements are nonnegative
  integers, the call fails with reason <c>badarg</c>.
 </p>
<p><em>See also:</em> <seealso marker="#new-2">new/2</seealso>, <seealso marker="#to_orddict-1">to_orddict/1</seealso>.</p>
</desc></func>
<func>
<name name="get" arity="2"/>
<fsummary>Get the value of entry I.</fsummary>

<desc><marker id="get-2"/>

<p>Get the value of entry <c><anno>I</anno></c>. If <c><anno>I</anno></c> is not a nonnegative
  integer, or if the array has fixed size and <c><anno>I</anno></c> is larger than the
  maximum index, the call fails with reason <c>badarg</c>.</p>
 
  <p>If the array does not have fixed size, this function will return the
  default value for any index <c><anno>I</anno></c> greater than <c>size(<anno>Array</anno>)-1</c>.</p>
<p><em>See also:</em> <seealso marker="#set-3">set/3</seealso>.</p>
</desc></func>
<func>
<name name="is_array" arity="1"/>
<fsummary>Returns true if X appears to be an array, otherwise false.</fsummary>

<desc><marker id="is_array-1"/>

<p>Returns <c>true</c> if <c><anno>X</anno></c> appears to be an array, otherwise <c>false</c>.
  Note that the check is only shallow; there is no guarantee that <c><anno>X</anno></c>
  is a well-formed array representation even if this function returns
  <c>true</c>.</p>
</desc></func>
<func>
<name name="is_fix" arity="1"/>
<fsummary>Check if the array has fixed size.</fsummary>

<desc><marker id="is_fix-1"/>

<p>Check if the array has fixed size.
  Returns <c>true</c> if the array is fixed, otherwise <c>false</c>.</p>
<p><em>See also:</em> <seealso marker="#fix-1">fix/1</seealso>.</p>
</desc></func>
<func>
<name name="map" arity="2"/>
<fsummary>Map the given function onto each element of the array.</fsummary>
<desc><marker id="map-2"/>

<p>Map the given function onto each element of the array. The
  elements are visited in order from the lowest index to the highest.
  If <c><anno>Function</anno></c> is not a function, the call fails with reason <c>badarg</c>.
 </p>
<p><em>See also:</em> <seealso marker="#foldl-3">foldl/3</seealso>, <seealso marker="#foldr-3">foldr/3</seealso>, <seealso marker="#sparse_map-2">sparse_map/2</seealso>.</p>
</desc></func>
<func>
<name name="new" arity="0"/>
<fsummary>Create a new, extendible array with initial size zero.</fsummary>

<desc><marker id="new-0"/>

<p>Create a new, extendible array with initial size zero.</p>
<p><em>See also:</em> <seealso marker="#new-1">new/1</seealso>, <seealso marker="#new-2">new/2</seealso>.</p>
</desc></func>
<func>
<name name="new" arity="1"/>
<fsummary>Create a new array according to the given options.</fsummary>

<desc><marker id="new-1"/>

<p>Create a new array according to the given options. By default,  
the array is extendible and has initial size zero. Array indices  
start at 0.</p>
 
  <p><c><anno>Options</anno></c> is a single term or a list of terms, selected from the
  following:
  </p><taglist>
    <tag><c>N::integer() >= 0</c> or <c>{size, N::integer() >= 0}</c></tag>
    <item><p>Specifies the initial size of the array; this also implies
    <c>{fixed, true}</c>. If <c>N</c> is not a nonnegative integer, the call
    fails with reason <c>badarg</c>.</p></item>
    <tag><c>fixed</c> or <c>{fixed, true}</c></tag>
    <item><p>Creates a fixed-size array; see also <seealso marker="#fix-1">fix/1</seealso>.</p></item>
    <tag><c>{fixed, false}</c></tag>
    <item><p>Creates an extendible (non fixed-size) array.</p></item>
    <tag><c>{default, Value}</c></tag>
    <item><p>Sets the default value for the array to <c>Value</c>.</p></item>
  </taglist><p>  
Options are processed in the order they occur in the list, i.e.,  
later options have higher precedence.</p>
 
  <p>The default value is used as the value of uninitialized entries, and  
cannot be changed once the array has been created.</p>
 
  <p>Examples:
  </p><pre>     array:new(100)</pre><p> creates a fixed-size array of size 100.
  </p><pre>     array:new({default,0})</pre><p> creates an empty, extendible array
  whose default value is 0.
  </p><pre>     array:new([{size,10},{fixed,false},{default,-1}])</pre><p> creates an
  extendible array with initial size 10 whose default value is -1.
 </p>
<p><em>See also:</em> <seealso marker="#fix-1">fix/1</seealso>, <seealso marker="#from_list-2">from_list/2</seealso>, <seealso marker="#get-2">get/2</seealso>, <seealso marker="#new-0">new/0</seealso>, <seealso marker="#new-2">new/2</seealso>, <seealso marker="#set-3">set/3</seealso>.</p>
</desc></func>
<func>
<name name="new" arity="2"/>
<fsummary>Create a new array according to the given size and options.</fsummary>

<desc><marker id="new-2"/>

<p>Create a new array according to the given size and options. If
  <c><anno>Size</anno></c> is not a nonnegative integer, the call fails with reason
  <c>badarg</c>. By default, the array has fixed size. Note that any size
  specifications in <c><anno>Options</anno></c> will override the <c><anno>Size</anno></c> parameter.</p>
 
  <p>If <c><anno>Options</anno></c> is a list, this is simply equivalent to <c>new([{size,
  <anno>Size</anno>} | <anno>Options</anno>]</c>, otherwise it is equivalent to <c>new([{size, <anno>Size</anno>} |
  [<anno>Options</anno>]]</c>. However, using this function directly is more efficient.</p>
 
  <p>Example:
  </p><pre>     array:new(100, {default,0})</pre><p> creates a fixed-size array of size
  100, whose default value is 0.
 </p>
<p><em>See also:</em> <seealso marker="#new-1">new/1</seealso>.</p>
</desc></func>
<func>
<name name="relax" arity="1"/>
<fsummary>Make the array resizable.</fsummary>

<desc><marker id="relax-1"/>

<p>Make the array resizable. (Reverses the effects of <seealso marker="#fix-1">fix/1</seealso>.)</p>
<p><em>See also:</em> <seealso marker="#fix-1">fix/1</seealso>.</p>
</desc></func>
<func>
<name name="reset" arity="2"/>
<fsummary>Reset entry I to the default value for the array.</fsummary>

<desc><marker id="reset-2"/>

<p>Reset entry <c><anno>I</anno></c> to the default value for the array.
  If the value of entry <c><anno>I</anno></c> is the default value the array will be
  returned unchanged. Reset will never change size of the array.   
  Shrinking can be done explicitly by calling <seealso marker="#resize-2">resize/2</seealso>.</p>
 
  <p>If <c><anno>I</anno></c> is not a nonnegative integer, or if the array has fixed size
  and <c><anno>I</anno></c> is larger than the maximum index, the call fails with reason
  <c>badarg</c>; cf. <seealso marker="#set-3">set/3</seealso>
 </p>
<p><em>See also:</em> <seealso marker="#new-2">new/2</seealso>, <seealso marker="#set-3">set/3</seealso>.</p>
</desc></func>
<func>
<name name="resize" arity="1"/>
<fsummary>Change the size of the array to that reported by sparse_size/1.</fsummary>

<desc><marker id="resize-1"/>

<p>Change the size of the array to that reported by <seealso marker="#sparse_size-1">sparse_size/1</seealso>. If the given array has fixed size, the resulting
  array will also have fixed size.</p>
<p><em>See also:</em> <seealso marker="#resize-2">resize/2</seealso>, <seealso marker="#sparse_size-1">sparse_size/1</seealso>.</p>
</desc></func>
<func>
<name name="resize" arity="2"/>
<fsummary>Change the size of the array.</fsummary>

<desc><marker id="resize-2"/>

<p>Change the size of the array. If <c><anno>Size</anno></c> is not a nonnegative
  integer, the call fails with reason <c>badarg</c>. If the given array has
  fixed size, the resulting array will also have fixed size.</p>
</desc></func>
<func>
<name name="set" arity="3"/>
<fsummary>Set entry I of the array to Value.</fsummary>

<desc><marker id="set-3"/>

<p>Set entry <c><anno>I</anno></c> of the array to <c><anno>Value</anno></c>. If <c><anno>I</anno></c> is not a
  nonnegative integer, or if the array has fixed size and <c><anno>I</anno></c> is larger
  than the maximum index, the call fails with reason <c>badarg</c>.</p>
 
  <p>If the array does not have fixed size, and <c><anno>I</anno></c> is greater than
  <c>size(<anno>Array</anno>)-1</c>, the array will grow to size <c><anno>I</anno>+1</c>.
 </p>
<p><em>See also:</em> <seealso marker="#get-2">get/2</seealso>, <seealso marker="#reset-2">reset/2</seealso>.</p>
</desc></func>
<func>
<name name="size" arity="1"/>
<fsummary>Get the number of entries in the array.</fsummary>

<desc><marker id="size-1"/>

<p>Get the number of entries in the array. Entries are numbered
  from 0 to <c>size(<anno>Array</anno>)-1</c>; hence, this is also the index of the first
  entry that is guaranteed to not have been previously set.</p>
<p><em>See also:</em> <seealso marker="#set-3">set/3</seealso>, <seealso marker="#sparse_size-1">sparse_size/1</seealso>.</p>
</desc></func>
<func>
<name name="sparse_foldl" arity="3"/>
<fsummary>Fold the elements of the array using the given function and
  initial accumulator value, skipping default-valued entries.</fsummary>
<desc><marker id="sparse_foldl-3"/>

<p>Fold the elements of the array using the given function and
  initial accumulator value, skipping default-valued entries. The
  elements are visited in order from the lowest index to the highest.
  If <c><anno>Function</anno></c> is not a function, the call fails with reason <c>badarg</c>.
 </p>
<p><em>See also:</em> <seealso marker="#foldl-3">foldl/3</seealso>, <seealso marker="#sparse_foldr-3">sparse_foldr/3</seealso>.</p>
</desc></func>
<func>
<name name="sparse_foldr" arity="3"/>
<fsummary>Fold the elements of the array right-to-left using the given
  function and initial accumulator value, skipping default-valued
  entries.</fsummary>
<desc><marker id="sparse_foldr-3"/>

<p>Fold the elements of the array right-to-left using the given
  function and initial accumulator value, skipping default-valued
  entries. The elements are visited in order from the highest index to
  the lowest. If <c><anno>Function</anno></c> is not a function, the call fails with
  reason <c>badarg</c>.
 </p>
<p><em>See also:</em> <seealso marker="#foldr-3">foldr/3</seealso>, <seealso marker="#sparse_foldl-3">sparse_foldl/3</seealso>.</p>
</desc></func>
<func>
<name name="sparse_map" arity="2"/>
<fsummary>Map the given function onto each element of the array, skipping
  default-valued entries.</fsummary>
<desc><marker id="sparse_map-2"/>

<p>Map the given function onto each element of the array, skipping
  default-valued entries. The elements are visited in order from the
  lowest index to the highest. If <c><anno>Function</anno></c> is not a function, the
  call fails with reason <c>badarg</c>.
 </p>
<p><em>See also:</em> <seealso marker="#map-2">map/2</seealso>.</p>
</desc></func>
<func>
<name name="sparse_size" arity="1"/>
<fsummary>Get the number of entries in the array up until the last
  non-default valued entry.</fsummary>

<desc><marker id="sparse_size-1"/>

<p>Get the number of entries in the array up until the last
  non-default valued entry. In other words, returns <c>I+1</c> if <c>I</c> is the
  last non-default valued entry in the array, or zero if no such entry
  exists.</p>
<p><em>See also:</em> <seealso marker="#resize-1">resize/1</seealso>, <seealso marker="#size-1">size/1</seealso>.</p>
</desc></func>
<func>
<name name="sparse_to_list" arity="1"/>
<fsummary>Converts the array to a list, skipping default-valued entries.</fsummary>

<desc><marker id="sparse_to_list-1"/>

<p>Converts the array to a list, skipping default-valued entries.
 </p>
<p><em>See also:</em> <seealso marker="#to_list-1">to_list/1</seealso>.</p>
</desc></func>
<func>
<name name="sparse_to_orddict" arity="1"/>
<fsummary>Convert the array to an ordered list of pairs {Index, Value},
  skipping default-valued entries.</fsummary>

<desc><marker id="sparse_to_orddict-1"/>

<p>Convert the array to an ordered list of pairs <c>{Index, Value}</c>,
  skipping default-valued entries.
 </p>
<p><em>See also:</em> <seealso marker="#to_orddict-1">to_orddict/1</seealso>.</p>
</desc></func>
<func>
<name name="to_list" arity="1"/>
<fsummary>Converts the array to a list.</fsummary>

<desc><marker id="to_list-1"/>

<p>Converts the array to a list.
 </p>
<p><em>See also:</em> <seealso marker="#from_list-2">from_list/2</seealso>, <seealso marker="#sparse_to_list-1">sparse_to_list/1</seealso>.</p>
</desc></func>
<func>
<name name="to_orddict" arity="1"/>
<fsummary>Convert the array to an ordered list of pairs {Index, Value}.</fsummary>

<desc><marker id="to_orddict-1"/>

<p>Convert the array to an ordered list of pairs <c>{Index, Value}</c>.
 </p>
<p><em>See also:</em> <seealso marker="#from_orddict-2">from_orddict/2</seealso>, <seealso marker="#sparse_to_orddict-1">sparse_to_orddict/1</seealso>.</p>
</desc></func></funcs>

</erlref>