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Diffstat (limited to 'lib/stdlib/doc/src/dict.xml')
| -rw-r--r-- | lib/stdlib/doc/src/dict.xml | 208 |
1 files changed, 119 insertions, 89 deletions
diff --git a/lib/stdlib/doc/src/dict.xml b/lib/stdlib/doc/src/dict.xml index 20bab99a9c..c926ff1b5b 100644 --- a/lib/stdlib/doc/src/dict.xml +++ b/lib/stdlib/doc/src/dict.xml @@ -29,12 +29,13 @@ <rev>B</rev> </header> <module>dict</module> - <modulesummary>Key-Value Dictionary</modulesummary> + <modulesummary>Key-value dictionary.</modulesummary> <description> - <p><c>Dict</c> implements a <c>Key</c> - <c>Value</c> dictionary. + <p>This module provides a <c>Key</c>-<c>Value</c> dictionary. The representation of a dictionary is not defined.</p> - <p>This module provides exactly the same interface as the module - <c>orddict</c>. One difference is that while this module + <p>This module provides the same interface as the + <seealso marker="orddict"><c>orddict(3)</c></seealso> module. + One difference is that while this module considers two keys as different if they do not match (<c>=:=</c>), <c>orddict</c> considers two keys as different if and only if they do not compare equal (<c>==</c>).</p> @@ -43,211 +44,241 @@ <datatypes> <datatype> <name name="dict" n_vars="2"/> - <desc><p>Dictionary as returned by <c>new/0</c>.</p></desc> + <desc><p>Dictionary as returned by + <seealso marker="#new/0"><c>new/0</c></seealso>.</p> + </desc> </datatype> <datatype> <name name="dict" n_vars="0"/> </datatype> </datatypes> + <funcs> <func> <name name="append" arity="3"/> - <fsummary>Append a value to keys in a dictionary</fsummary> + <fsummary>Append a value to keys in a dictionary.</fsummary> <desc> - <p>This function appends a new <c><anno>Value</anno></c> to the current list + <p>Appends a new <c><anno>Value</anno></c> to the current list of values associated with <c><anno>Key</anno></c>.</p> + <p>See also section <seealso marker="#notes">Notes</seealso>.</p> </desc> </func> + <func> <name name="append_list" arity="3"/> - <fsummary>Append new values to keys in a dictionary</fsummary> + <fsummary>Append new values to keys in a dictionary.</fsummary> <desc> - <p>This function appends a list of values <c><anno>ValList</anno></c> to + <p>Appends a list of values <c><anno>ValList</anno></c> to the current list of values associated with <c><anno>Key</anno></c>. An exception is generated if the initial value associated with <c><anno>Key</anno></c> is not a list of values.</p> + <p>See also section <seealso marker="#notes">Notes</seealso>.</p> </desc> </func> + <func> <name name="erase" arity="2"/> - <fsummary>Erase a key from a dictionary</fsummary> + <fsummary>Erase a key from a dictionary.</fsummary> <desc> - <p>This function erases all items with a given key from a - dictionary.</p> + <p>Erases all items with a given key from a dictionary.</p> </desc> </func> + <func> <name name="fetch" arity="2"/> - <fsummary>Look-up values in a dictionary</fsummary> + <fsummary>Look up values in a dictionary.</fsummary> <desc> - <p>This function returns the value associated with <c><anno>Key</anno></c> - in the dictionary <c><anno>Dict</anno></c>. <c>fetch</c> assumes that - the <c><anno>Key</anno></c> is present in the dictionary and an exception + <p>Returns the value associated with <c><anno>Key</anno></c> + in dictionary <c><anno>Dict</anno></c>. This function assumes that + <c><anno>Key</anno></c> is present in dictionary <c>Dict</c>, + and an exception is generated if <c><anno>Key</anno></c> is not in the dictionary.</p> + <p>See also section <seealso marker="#notes">Notes</seealso>.</p> </desc> </func> + <func> <name name="fetch_keys" arity="1"/> - <fsummary>Return all keys in a dictionary</fsummary> + <fsummary>Return all keys in a dictionary.</fsummary> <desc> - <p>This function returns a list of all keys in the dictionary.</p> + <p>Returns a list of all keys in dictionary <c>Dict</c>.</p> </desc> </func> + <func> <name name="filter" arity="2"/> - <fsummary>Choose elements which satisfy a predicate</fsummary> + <fsummary>Select elements that satisfy a predicate.</fsummary> <desc> <p><c><anno>Dict2</anno></c> is a dictionary of all keys and values in - <c><anno>Dict1</anno></c> for which <c><anno>Pred</anno>(<anno>Key</anno>, <anno>Value</anno>)</c> is <c>true</c>.</p> + <c><anno>Dict1</anno></c> for which + <c><anno>Pred</anno>(<anno>Key</anno>, <anno>Value</anno>)</c> is + <c>true</c>.</p> </desc> </func> + <func> <name name="find" arity="2"/> - <fsummary>Search for a key in a dictionary</fsummary> + <fsummary>Search for a key in a dictionary.</fsummary> <desc> - <p>This function searches for a key in a dictionary. Returns - <c>{ok, <anno>Value</anno>}</c> where <c><anno>Value</anno></c> is the value associated - with <c><anno>Key</anno></c>, or <c>error</c> if the key is not present in - the dictionary.</p> + <p>Searches for a key in dictionary <c>Dict</c>. Returns + <c>{ok, <anno>Value</anno>}</c>, where <c><anno>Value</anno></c> is + the value associated with <c><anno>Key</anno></c>, or <c>error</c> + if the key is not present in the dictionary.</p> + <p>See also section <seealso marker="#notes">Notes</seealso>.</p> </desc> </func> + <func> <name name="fold" arity="3"/> - <fsummary>Fold a function over a dictionary</fsummary> + <fsummary>Fold a function over a dictionary.</fsummary> <desc> <p>Calls <c><anno>Fun</anno></c> on successive keys and values of - <c><anno>Dict</anno></c> together with an extra argument <c>Acc</c> + dictionary <c><anno>Dict</anno></c> together with an extra argument + <c>Acc</c> (short for accumulator). <c><anno>Fun</anno></c> must return a new - accumulator which is passed to the next call. <c><anno>Acc0</anno></c> is - returned if the dict is empty. The evaluation order is + accumulator that is passed to the next call. <c><anno>Acc0</anno></c> + is returned if the dictionary is empty. The evaluation order is undefined.</p> </desc> </func> + <func> <name name="from_list" arity="1"/> - <fsummary>Convert a list of pairs to a dictionary</fsummary> + <fsummary>Convert a list of pairs to a dictionary.</fsummary> <desc> - <p>This function converts the <c><anno>Key</anno></c> - <c><anno>Value</anno></c> list - <c><anno>List</anno></c> to a dictionary.</p> + <p>Converts the <c><anno>Key</anno></c>-<c><anno>Value</anno></c> list + <c><anno>List</anno></c> to dictionary <c>Dict</c>.</p> </desc> </func> + + <func> + <name name="is_empty" arity="1"/> + <fsummary>Return <c>true</c> if the dictionary is empty.</fsummary> + <desc> + <p>Returns <c>true</c> if dictionary <c><anno>Dict</anno></c> has no + elements, otherwise <c>false</c>.</p> + </desc> + </func> + <func> <name name="is_key" arity="2"/> - <fsummary>Test if a key is in a dictionary</fsummary> + <fsummary>Test if a key is in a dictionary.</fsummary> <desc> - <p>This function tests if <c><anno>Key</anno></c> is contained in - the dictionary <c><anno>Dict</anno></c>.</p> + <p>Tests if <c><anno>Key</anno></c> is contained in + dictionary <c><anno>Dict</anno></c>.</p> </desc> </func> + <func> <name name="map" arity="2"/> - <fsummary>Map a function over a dictionary</fsummary> + <fsummary>Map a function over a dictionary.</fsummary> <desc> - <p><c>map</c> calls <c><anno>Fun</anno></c> on successive keys and values - of <c><anno>Dict1</anno></c> to return a new value for each key. - The evaluation order is undefined.</p> + <p>Calls <c><anno>Fun</anno></c> on successive keys and values + of dictionary <c><anno>Dict1</anno></c> to return a new value for + each key. The evaluation order is undefined.</p> </desc> </func> + <func> <name name="merge" arity="3"/> - <fsummary>Merge two dictionaries</fsummary> + <fsummary>Merge two dictionaries.</fsummary> <desc> - <p><c>merge</c> merges two dictionaries, <c><anno>Dict1</anno></c> and - <c><anno>Dict2</anno></c>, to create a new dictionary. All the <c><anno>Key</anno></c> - - <c><anno>Value</anno></c> pairs from both dictionaries are included in - the new dictionary. If a key occurs in both dictionaries then - <c><anno>Fun</anno></c> is called with the key and both values to return a - new value. <c>merge</c> could be defined as:</p> + <p>Merges two dictionaries, <c><anno>Dict1</anno></c> and + <c><anno>Dict2</anno></c>, to create a new dictionary. All the + <c><anno>Key</anno></c>-<c><anno>Value</anno></c> pairs from both + dictionaries are included in the new dictionary. If a key occurs + in both dictionaries, <c><anno>Fun</anno></c> is called with the + key and both values to return a new value. + <c>merge</c> can be defined as follows, but is faster:</p> <code type="none"> merge(Fun, D1, D2) -> fold(fun (K, V1, D) -> update(K, fun (V2) -> Fun(K, V1, V2) end, V1, D) end, D2, D1).</code> - <p>but is faster.</p> </desc> </func> + <func> <name name="new" arity="0"/> - <fsummary>Create a dictionary</fsummary> + <fsummary>Create a dictionary.</fsummary> <desc> - <p>This function creates a new dictionary.</p> + <p>Creates a new dictionary.</p> </desc> </func> + <func> <name name="size" arity="1"/> - <fsummary>Return the number of elements in a dictionary</fsummary> + <fsummary>Return the number of elements in a dictionary.</fsummary> <desc> - <p>Returns the number of elements in a <c><anno>Dict</anno></c>.</p> - </desc> - </func> - <func> - <name name="is_empty" arity="1"/> - <fsummary>Return true if the dictionary is empty</fsummary> - <desc> - <p>Returns <c>true</c> if <c><anno>Dict</anno></c> has no elements, <c>false</c> otherwise.</p> + <p>Returns the number of elements in dictionary + <c><anno>Dict</anno></c>.</p> </desc> </func> + <func> <name name="store" arity="3"/> - <fsummary>Store a value in a dictionary</fsummary> + <fsummary>Store a value in a dictionary.</fsummary> <desc> - <p>This function stores a <c><anno>Key</anno></c> - <c><anno>Value</anno></c> pair in a - dictionary. If the <c><anno>Key</anno></c> already exists in <c><anno>Dict1</anno></c>, + <p>Stores a <c><anno>Key</anno></c>-<c><anno>Value</anno></c> pair in + dictionary <c>Dict2</c>. If <c><anno>Key</anno></c> already exists in + <c><anno>Dict1</anno></c>, the associated value is replaced by <c><anno>Value</anno></c>.</p> </desc> </func> + <func> <name name="to_list" arity="1"/> - <fsummary>Convert a dictionary to a list of pairs</fsummary> + <fsummary>Convert a dictionary to a list of pairs.</fsummary> <desc> - <p>This function converts the dictionary to a list - representation.</p> + <p>Converts dictionary <c>Dict</c> to a list representation.</p> </desc> </func> + <func> <name name="update" arity="3"/> - <fsummary>Update a value in a dictionary</fsummary> + <fsummary>Update a value in a dictionary.</fsummary> <desc> - <p>Update a value in a dictionary by calling <c><anno>Fun</anno></c> on - the value to get a new value. An exception is generated if + <p>Updates a value in a dictionary by calling <c><anno>Fun</anno></c> on + the value to get a new value. An exception is generated if <c><anno>Key</anno></c> is not present in the dictionary.</p> </desc> </func> + <func> <name name="update" arity="4"/> - <fsummary>Update a value in a dictionary</fsummary> + <fsummary>Update a value in a dictionary.</fsummary> <desc> - <p>Update a value in a dictionary by calling <c><anno>Fun</anno></c> on - the value to get a new value. If <c><anno>Key</anno></c> is not present - in the dictionary then <c><anno>Initial</anno></c> will be stored as - the first value. For example <c>append/3</c> could be defined - as:</p> + <p>Updates a value in a dictionary by calling <c><anno>Fun</anno></c> on + the value to get a new value. If <c><anno>Key</anno></c> is not + present in the dictionary, <c><anno>Initial</anno></c> is stored as + the first value. For example, <c>append/3</c> can be defined as:</p> <code type="none"> append(Key, Val, D) -> update(Key, fun (Old) -> Old ++ [Val] end, [Val], D).</code> </desc> </func> + <func> <name name="update_counter" arity="3"/> - <fsummary>Increment a value in a dictionary</fsummary> + <fsummary>Increment a value in a dictionary.</fsummary> <desc> - <p>Add <c><anno>Increment</anno></c> to the value associated with <c><anno>Key</anno></c> - and store this value. If <c><anno>Key</anno></c> is not present in - the dictionary then <c><anno>Increment</anno></c> will be stored as - the first value.</p> - <p>This could be defined as:</p> + <p>Adds <c><anno>Increment</anno></c> to the value associated with + <c><anno>Key</anno></c> and stores this value. + If <c><anno>Key</anno></c> is not present in the dictionary, + <c><anno>Increment</anno></c> is stored as the first value.</p> + <p>This can be defined as follows, but is faster:</p> <code type="none"> update_counter(Key, Incr, D) -> update(Key, fun (Old) -> Old + Incr end, Incr, D).</code> - <p>but is faster.</p> </desc> </func> </funcs> <section> <title>Notes</title> - <p>The functions <c>append</c> and <c>append_list</c> are included - so we can store keyed values in a list <em>accumulator</em>. For + <marker id="notes"/> + <p>Functions <c>append</c> and <c>append_list</c> are included + so that keyed values can be stored in a list <em>accumulator</em>, for example:</p> <pre> > D0 = dict:new(), @@ -256,19 +287,18 @@ update_counter(Key, Incr, D) -> D3 = dict:append(files, f2, D2), D4 = dict:append(files, f3, D3), dict:fetch(files, D4). -[f1,f2,f3] </pre> +[f1,f2,f3]</pre> <p>This saves the trouble of first fetching a keyed value, appending a new value to the list of stored values, and storing - the result. - </p> - <p>The function <c>fetch</c> should be used if the key is known to - be in the dictionary, otherwise <c>find</c>.</p> + the result.</p> + <p>Function <c>fetch</c> is to be used if the key is known to + be in the dictionary, otherwise function <c>find</c>.</p> </section> <section> <title>See Also</title> - <p><seealso marker="gb_trees">gb_trees(3)</seealso>, - <seealso marker="orddict">orddict(3)</seealso></p> + <p><seealso marker="gb_trees"><c>gb_trees(3)</c></seealso>, + <seealso marker="orddict"><c>orddict(3)</c></seealso></p> </section> </erlref> |