<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE erlref SYSTEM "erlref.dtd">
<erlref>
<header>
<copyright>
<year>2007</year><year>2016</year>
<holder>Ericsson AB. All Rights Reserved.</holder>
</copyright>
<legalnotice>
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
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<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 data structures, for example,
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 that has been explicitly set to the same value
as the default one (compare
<seealso marker="#reset-2"><c>reset/2</c></seealso>). If you need to
differentiate between unset and set entries, ensure 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
to set an entry successfully, all indices in the range [0,<c>I</c>] stay
accessible unless the array size is explicitly changed by calling
<seealso marker="#resize-2"><c>resize/2</c></seealso>.</p>
<p><em>Examples:</em></p>
<p>Create a fixed-size array with entries 0-9 set to <c>undefined</c>:</p>
<pre>
A0 = array:new(10).
10 = array:size(A0).</pre>
<p>Create an extendible array and set entry 17 to <c>true</c>, causing the
array to grow automatically:</p>
<pre>
A1 = array:set(17, true, array:new()).
18 = array:size(A1).</pre>
<p>Read back a stored value:</p>
<pre>
true = array:get(17, A1).</pre>
<p>Accessing an unset entry returns default value:</p>
<pre>
undefined = array:get(3, A1)</pre>
<p>Accessing an entry beyond the last set entry also returns the default
value, if the array does not have fixed size:</p>
<pre>
undefined = array:get(18, A1).</pre>
<p>"Sparse" functions ignore default-valued entries:</p>
<pre>
A2 = array:set(4, false, A1).
[{4, false}, {17, true}] = array:sparse_to_orddict(A2).</pre>
<p>An extendible array can be made fixed-size later:</p>
<pre>
A3 = array:fix(A2).</pre>
<p>A fixed-size array does not grow automatically and does not allow
accesses beyond the last set entry:</p>
<pre>
{'EXIT',{badarg,_}} = (catch array:set(18, true, A3)).
{'EXIT',{badarg,_}} = (catch array:get(18, A3)).</pre>
</description>
<datatypes>
<datatype>
<name name="array" n_vars="1"/>
<desc>
<p>A functional, extendible array. The representation is not documented
and is subject to change without notice. Notice that arrays cannot be
directly compared for equality.</p>
</desc>
</datatype>
<datatype>
<name name="array" n_vars="0"/>
</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>Gets the value used for uninitialized entries.</p>
<p>See also <seealso marker="#new-2"><c>new/2</c></seealso>.</p>
</desc>
</func>
<func>
<name name="fix" arity="1"/>
<fsummary>Fix the array size.</fsummary>
<desc><marker id="fix-1"/>
<p>Fixes the array size. This prevents it from growing automatically
upon insertion.</p>
<p>See also <seealso marker="#set-3"><c>set/3</c></seealso> and
<seealso marker="#relax-1"><c>relax/1</c></seealso>.</p>
</desc>
</func>
<func>
<name name="foldl" arity="3"/>
<fsummary>Fold the array elements using the specified function and initial
accumulator value.</fsummary>
<desc><marker id="foldl-3"/>
<p>Folds the array elements using the specified 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>See also <seealso marker="#foldr-3"><c>foldr/3</c></seealso>,
<seealso marker="#map-2"><c>map/2</c></seealso>,
<seealso marker="#sparse_foldl-3"><c>sparse_foldl/3</c></seealso>.</p>
</desc>
</func>
<func>
<name name="foldr" arity="3"/>
<fsummary>Fold the array elements right-to-left using the specified
function and initial accumulator value.</fsummary>
<desc><marker id="foldr-3"/>
<p>Folds the array elements right-to-left using the specified 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>See also <seealso marker="#foldl-3"><c>foldl/3</c></seealso>,
<seealso marker="#map-2"><c>map/2</c></seealso>.</p>
</desc>
</func>
<func>
<name name="from_list" arity="1"/>
<fsummary>Equivalent to <c>from_list(List, undefined)</c>.</fsummary>
<desc><marker id="from_list-1"/>
<p>Equivalent to
<seealso marker="#from_list-2"><c>from_list(<anno>List</anno>, undefined)</c></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>Converts 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>See also <seealso marker="#new-2"><c>new/2</c></seealso>,
<seealso marker="#to_list-1"><c>to_list/1</c></seealso>.</p>
</desc>
</func>
<func>
<name name="from_orddict" arity="1"/>
<fsummary>Equivalent to <c>from_orddict(Orddict, undefined)</c>.
</fsummary>
<desc><marker id="from_orddict-1"/>
<p>Equivalent to
<seealso marker="#from_orddict-2"><c>from_orddict(<anno>Orddict</anno>, undefined)</c></seealso>.</p>
</desc>
</func>
<func>
<name name="from_orddict" arity="2"/>
<fsummary>Convert an ordered list of pairs <c>{Index, Value}</c> to a
corresponding extendible array.</fsummary>
<desc><marker id="from_orddict-2"/>
<p>Converts an ordered list of pairs <c>{Index, <anno>Value</anno>}</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 non-negative integers, the call fails with
reason <c>badarg</c>.</p>
<p>See also <seealso marker="#new-2"><c>new/2</c></seealso>,
<seealso marker="#to_orddict-1"><c>to_orddict/1</c></seealso>.</p>
</desc>
</func>
<func>
<name name="get" arity="2"/>
<fsummary>Get the value of entry <c>I</c>.</fsummary>
<desc><marker id="get-2"/>
<p>Gets the value of entry <c><anno>I</anno></c>. If
<c><anno>I</anno></c> is not a non-negative 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, the default value for any
index <c><anno>I</anno></c> greater than
<c>size(<anno>Array</anno>)-1</c> is returned.</p>
<p>See also <seealso marker="#set-3"><c>set/3</c></seealso>.</p>
</desc>
</func>
<func>
<name name="is_array" arity="1"/>
<fsummary>Returns <c>true</c> if <c>X</c> is an array, otherwise
<c>false</c>.</fsummary>
<desc><marker id="is_array-1"/>
<p>Returns <c>true</c> if <c><anno>X</anno></c> is an array, otherwise
<c>false</c>. Notice that the check is only shallow, as 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>Checks if the array has fixed size. Returns <c>true</c> if the array
is fixed, otherwise <c>false</c>.</p>
<p>See also <seealso marker="#fix-1"><c>fix/1</c></seealso>.</p>
</desc>
</func>
<func>
<name name="map" arity="2"/>
<fsummary>Map the specified function onto each array element.</fsummary>
<desc><marker id="map-2"/>
<p>Maps the specified function onto each array element. 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>See also <seealso marker="#foldl-3"><c>foldl/3</c></seealso>,
<seealso marker="#foldr-3"><c>foldr/3</c></seealso>,
<seealso marker="#sparse_map-2"><c>sparse_map/2</c></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>Creates a new, extendible array with initial size zero.</p>
<p>See also <seealso marker="#new-1"><c>new/1</c></seealso>,
<seealso marker="#new-2"><c>new/2</c></seealso>.</p>
</desc>
</func>
<func>
<name name="new" arity="1"/>
<fsummary>Create a new array according to the specified options.
</fsummary>
<desc><marker id="new-1"/>
<p>Creates a new array according to the specified otions. By default,
the array is extendible and has initial size zero. Array indices
start at <c>0</c>.</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 array size; this also implies
<c>{fixed, true}</c>. If <c>N</c> is not a non-negative 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"><c>fix/1</c></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, that is,
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><em>Examples:</em></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 <c>0</c>.
</p>
<pre>
array:new([{size,10},{fixed,false},{default,-1}])</pre>
<p>creates an extendible array with initial size 10 whose default value
is <c>-1</c>.</p>
<p>See also <seealso marker="#fix-1"><c>fix/1</c></seealso>,
<seealso marker="#from_list-2"><c>from_list/2</c></seealso>,
<seealso marker="#get-2"><c>get/2</c></seealso>,
<seealso marker="#new-0"><c>new/0</c></seealso>,
<seealso marker="#new-2"><c>new/2</c></seealso>,
<seealso marker="#set-3"><c>set/3</c></seealso>.</p>
</desc>
</func>
<func>
<name name="new" arity="2"/>
<fsummary>Create a new array according to the specified size and options.
</fsummary>
<desc><marker id="new-2"/>
<p>Creates a new array according to the specified size and options. If
<c><anno>Size</anno></c> is not a non-negative integer, the call fails
with reason <c>badarg</c>. By default, the array has fixed size.
Notice that any size specifications in <c><anno>Options</anno></c>
override parameter <c><anno>Size</anno></c>.</p>
<p>If <c><anno>Options</anno></c> is a list, this is 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><em>Example:</em></p>
<pre>
array:new(100, {default,0})</pre>
<p>creates a fixed-size array of size 100, whose default value is
<c>0</c>.</p>
<p>See also <seealso marker="#new-1"><c>new/1</c></seealso>.</p>
</desc>
</func>
<func>
<name name="relax" arity="1"/>
<fsummary>Make the array resizable.</fsummary>
<desc><marker id="relax-1"/>
<p>Makes the array resizable. (Reverses the effects of
<seealso marker="#fix-1"><c>fix/1</c></seealso>.)</p>
<p>See also <seealso marker="#fix-1"><c>fix/1</c></seealso>.</p>
</desc>
</func>
<func>
<name name="reset" arity="2"/>
<fsummary>Reset entry <c>I</c> to the default value for the array.
</fsummary>
<desc><marker id="reset-2"/>
<p>Resets 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 is returned unchanged. Reset never changes the array
size. Shrinking can be done explicitly by calling
<seealso marker="#resize-2"><c>resize/2</c></seealso>.</p>
<p>If <c><anno>I</anno></c> is not a non-negative 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>; compare
<seealso marker="#set-3"><c>set/3</c></seealso></p>
<p>See also <seealso marker="#new-2"><c>new/2</c></seealso>,
<seealso marker="#set-3"><c>set/3</c></seealso>.</p>
</desc>
</func>
<func>
<name name="resize" arity="1"/>
<fsummary>Change the array size to that reported by <c>sparse_size/1</c>.
</fsummary>
<desc><marker id="resize-1"/>
<p>Changes the array size to that reported by
<seealso marker="#sparse_size-1"><c>sparse_size/1</c></seealso>. If
the specified array has fixed size, also the resulting array has fixed
size.</p>
<p>See also <seealso marker="#resize-2"><c>resize/2</c></seealso>,
<seealso marker="#sparse_size-1"><c>sparse_size/1</c></seealso>.</p>
</desc>
</func>
<func>
<name name="resize" arity="2"/>
<fsummary>Change the array size.</fsummary>
<desc><marker id="resize-2"/>
<p>Change the array size. If <c><anno>Size</anno></c> is not a
non-negative integer, the call fails with reason <c>badarg</c>. If
the specified array has fixed size, also the resulting array has fixed
size.</p>
</desc>
</func>
<func>
<name name="set" arity="3"/>
<fsummary>Set entry <c>I</c> of the array to <c>Value</c>.</fsummary>
<desc><marker id="set-3"/>
<p>Sets entry <c><anno>I</anno></c> of the array to
<c><anno>Value</anno></c>. If <c><anno>I</anno></c> is not a
non-negative 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 grows to
size <c><anno>I</anno>+1</c>.</p>
<p>See also <seealso marker="#get-2"><c>get/2</c></seealso>,
<seealso marker="#reset-2"><c>reset/2</c></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>Gets the number of entries in the array. Entries are numbered from
<c>0</c> 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>See also <seealso marker="#set-3"><c>set/3</c></seealso>,
<seealso marker="#sparse_size-1"><c>sparse_size/1</c></seealso>.</p>
</desc>
</func>
<func>
<name name="sparse_foldl" arity="3"/>
<fsummary>Fold the array elements using the specified function and initial
accumulator value, skipping default-valued entries.</fsummary>
<desc><marker id="sparse_foldl-3"/>
<p>Folds the array elements using the specified 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>See also <seealso marker="#foldl-3"><c>foldl/3</c></seealso>,
<seealso marker="#sparse_foldr-3"><c>sparse_foldr/3</c></seealso>.</p>
</desc>
</func>
<func>
<name name="sparse_foldr" arity="3"/>
<fsummary>Fold the array elements right-to-left using the specified
function and initial accumulator value, skipping default-valued
entries.</fsummary>
<desc><marker id="sparse_foldr-3"/>
<p>Folds the array elements right-to-left using the specified
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>See also <seealso marker="#foldr-3"><c>foldr/3</c></seealso>,
<seealso marker="#sparse_foldl-3"><c>sparse_foldl/3</c></seealso>.</p>
</desc>
</func>
<func>
<name name="sparse_map" arity="2"/>
<fsummary>Map the specified function onto each array element, skipping
default-valued entries.</fsummary>
<desc><marker id="sparse_map-2"/>
<p>Maps the specified function onto each array element, 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>See also <seealso marker="#map-2"><c>map/2</c></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>Gets the number of entries in the array up until the last
non-default-valued entry. That is, 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>See also <seealso marker="#resize-1"><c>resize/1</c></seealso>,
<seealso marker="#size-1"><c>size/1</c></seealso>.</p>
</desc>
</func>
<func>
<name name="sparse_to_list" arity="1"/>
<fsummary>Convert 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>See also <seealso marker="#to_list-1"><c>to_list/1</c></seealso>.</p>
</desc>
</func>
<func>
<name name="sparse_to_orddict" arity="1"/>
<fsummary>Convert the array to an ordered list of pairs <c>{Index,
Value}</c>, skipping default-valued entries.</fsummary>
<desc><marker id="sparse_to_orddict-1"/>
<p>Converts the array to an ordered list of pairs <c>{Index,
<anno>Value</anno>}</c>, skipping default-valued entries.</p>
<p>See also
<seealso marker="#to_orddict-1"><c>to_orddict/1</c></seealso>.</p>
</desc>
</func>
<func>
<name name="to_list" arity="1"/>
<fsummary>Convert the array to a list.</fsummary>
<desc><marker id="to_list-1"/>
<p>Converts the array to a list.</p>
<p>See also <seealso marker="#from_list-2"><c>from_list/2</c></seealso>,
<seealso marker="#sparse_to_list-1"><c>sparse_to_list/1</c></seealso>.
</p>
</desc>
</func>
<func>
<name name="to_orddict" arity="1"/>
<fsummary>Convert the array to an ordered list of pairs <c>{Index,
Value}</c>.</fsummary>
<desc><marker id="to_orddict-1"/>
<p>Converts the array to an ordered list of pairs <c>{Index,
<anno>Value</anno>}</c>.</p>
<p>See also
<seealso marker="#from_orddict-2"><c>from_orddict/2</c></seealso>,
<seealso marker="#sparse_to_orddict-1"><c>sparse_to_orddict/1</c></seealso>.
</p>
</desc>
</func>
</funcs>
</erlref>
