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Diffstat (limited to 'lib/stdlib/doc/src/queue.xml')
| -rw-r--r-- | lib/stdlib/doc/src/queue.xml | 354 |
1 files changed, 212 insertions, 142 deletions
diff --git a/lib/stdlib/doc/src/queue.xml b/lib/stdlib/doc/src/queue.xml index c1665a1ed4..9f3aff03a3 100644 --- a/lib/stdlib/doc/src/queue.xml +++ b/lib/stdlib/doc/src/queue.xml @@ -4,7 +4,7 @@ <erlref> <header> <copyright> - <year>1996</year><year>2014</year> + <year>1996</year><year>2016</year> <holder>Ericsson AB. All Rights Reserved.</holder> </copyright> <legalnotice> @@ -28,63 +28,74 @@ <docno>1</docno> <approved>Bjarne Däcker</approved> <checked></checked> - <date>97-01-15</date> + <date>1997-01-15</date> <rev>B</rev> - <file>queue.sgml</file> + <file>queue.xml</file> </header> <module>queue</module> - <modulesummary>Abstract Data Type for FIFO Queues</modulesummary> + <modulesummary>Abstract data type for FIFO queues.</modulesummary> <description> - <p>This module implements (double ended) FIFO queues + <p>This module provides (double-ended) FIFO queues in an efficient manner.</p> + <p>All functions fail with reason <c>badarg</c> if arguments - are of wrong type, for example queue arguments are not - queues, indexes are not integers, list arguments are + are of wrong type, for example, queue arguments are not + queues, indexes are not integers, and list arguments are not lists. Improper lists cause internal crashes. An index out of range for a queue also causes a failure with reason <c>badarg</c>.</p> + <p>Some functions, where noted, fail with reason <c>empty</c> for an empty queue.</p> + <p>The data representing a queue as used by this module - should be regarded as opaque by other modules. Any code + is to be regarded as opaque by other modules. Any code assuming knowledge of the format is running on thin ice.</p> + <p>All operations has an amortized O(1) running time, except - <c>len/1</c>, <c>join/2</c>, <c>split/2</c>, <c>filter/2</c> - and <c>member/2</c> that have O(n). + <seealso marker="#filter/2"><c>filter/2</c></seealso>, + <seealso marker="#join/2"><c>join/2</c></seealso>, + <seealso marker="#len/1"><c>len/1</c></seealso>, + <seealso marker="#member/2"><c>member/2</c></seealso>, + <seealso marker="#split/2"><c>split/2</c></seealso> that have O(n). To minimize the size of a queue minimizing the amount of garbage built by queue operations, the queues do not contain explicit length information, and that is why <c>len/1</c> is O(n). If better performance for this particular operation is essential, it is easy for the caller to keep track of the length.</p> - <p>Queues are double ended. The mental picture of + + <p>Queues are double-ended. The mental picture of a queue is a line of people (items) waiting for their turn. The queue front is the end with the item that has waited the longest. The queue rear is the end an item enters when it starts to wait. If instead using the mental picture of a list, the front is called head and the rear is called tail.</p> + <p>Entering at the front and exiting at the rear are reverse operations on the queue.</p> - <p>The module has several sets of interface functions. The - "Original API", the "Extended API" and the "Okasaki API".</p> + + <p>This module has three sets of interface functions: the + "Original API", the "Extended API", and the "Okasaki API".</p> + <p>The "Original API" and the "Extended API" both use the - mental picture of a waiting line of items. Both also + mental picture of a waiting line of items. Both have reverse operations suffixed "_r".</p> + <p>The "Original API" item removal functions return compound terms with both the removed item and the resulting queue. - The "Extended API" contain alternative functions that build - less garbage as well as functions for just inspecting the + The "Extended API" contains alternative functions that build + less garbage and functions for just inspecting the queue ends. Also the "Okasaki API" functions build less garbage.</p> - <p>The "Okasaki API" is inspired by "Purely Functional Data structures" + + <p>The "Okasaki API" is inspired by "Purely Functional Data Structures" by Chris Okasaki. It regards queues as lists. - The API is by many regarded as strange and avoidable. - For example many reverse operations have lexically reversed names, + This API is by many regarded as strange and avoidable. + For example, many reverse operations have lexically reversed names, some with more readable but perhaps less understandable aliases.</p> </description> - - <section> <title>Original API</title> </section> @@ -92,7 +103,8 @@ <datatypes> <datatype> <name name="queue" n_vars="1"/> - <desc><p>As returned by <c>new/0</c>.</p></desc> + <desc><p>As returned by + <seealso marker="#new/0"><c>new/0</c></seealso>.</p></desc> </datatype> <datatype> <name name="queue" n_vars="0"/> @@ -101,205 +113,229 @@ <funcs> <func> - <name name="new" arity="0"/> - <fsummary>Create an empty queue</fsummary> + <name name="filter" arity="2"/> + <fsummary>Filter a queue.</fsummary> <desc> - <p>Returns an empty queue.</p> + <p>Returns a queue <c><anno>Q2</anno></c> that is the result of calling + <c><anno>Fun</anno>(<anno>Item</anno>)</c> on all items in + <c><anno>Q1</anno></c>, in order from front to rear.</p> + <p>If <c><anno>Fun</anno>(<anno>Item</anno>)</c> returns <c>true</c>, + <c>Item</c> is copied to the result queue. If it returns <c>false</c>, + <c><anno>Item</anno></c> is not copied. If it returns a list, + the list elements are inserted instead of <c>Item</c> in the + result queue.</p> + <p>So, <c><anno>Fun</anno>(<anno>Item</anno>)</c> returning + <c>[<anno>Item</anno>]</c> is thereby + semantically equivalent to returning <c>true</c>, just + as returning <c>[]</c> is semantically equivalent to + returning <c>false</c>. But returning a list builds + more garbage than returning an atom.</p> </desc> </func> + <func> - <name name="is_queue" arity="1"/> - <fsummary>Test if a term is a queue</fsummary> + <name name="from_list" arity="1"/> + <fsummary>Convert a list to a queue.</fsummary> <desc> - <p>Tests if <c><anno>Term</anno></c> is a queue and returns <c>true</c> if so and - <c>false</c> otherwise.</p> + <p>Returns a queue containing the items in <c><anno>L</anno></c> in the + same order; the head item of the list becomes the front + item of the queue.</p> </desc> </func> + <func> - <name name="is_empty" arity="1"/> - <fsummary>Test if a queue is empty</fsummary> + <name name="in" arity="2"/> + <fsummary>Insert an item at the rear of a queue.</fsummary> <desc> - <p>Tests if <c><anno>Q</anno></c> is empty and returns <c>true</c> if so and - <c>false</c> otherwise.</p> + <p>Inserts <c><anno>Item</anno></c> at the rear of queue + <c><anno>Q1</anno></c>. + Returns the resulting queue <c><anno>Q2</anno></c>.</p> </desc> </func> + <func> - <name name="len" arity="1"/> - <fsummary>Get the length of a queue</fsummary> + <name name="in_r" arity="2"/> + <fsummary>Insert an item at the front of a queue.</fsummary> <desc> - <p>Calculates and returns the length of queue <c><anno>Q</anno></c>.</p> + <p>Inserts <c><anno>Item</anno></c> at the front of queue + <c><anno>Q1</anno></c>. + Returns the resulting queue <c><anno>Q2</anno></c>.</p> </desc> </func> <func> - <name name="in" arity="2"/> - <fsummary>Insert an item at the rear of a queue</fsummary> + <name name="is_empty" arity="1"/> + <fsummary>Test if a queue is empty.</fsummary> <desc> - <p>Inserts <c><anno>Item</anno></c> at the rear of queue <c><anno>Q1</anno></c>. - Returns the resulting queue <c><anno>Q2</anno></c>.</p> + <p>Tests if <c><anno>Q</anno></c> is empty and returns <c>true</c> if + so, otherwise otherwise.</p> </desc> </func> + <func> - <name name="in_r" arity="2"/> - <fsummary>Insert an item at the front of a queue</fsummary> + <name name="is_queue" arity="1"/> + <fsummary>Test if a term is a queue.</fsummary> <desc> - <p>Inserts <c><anno>Item</anno></c> at the front of queue <c><anno>Q1</anno></c>. - Returns the resulting queue <c><anno>Q2</anno></c>.</p> + <p>Tests if <c><anno>Term</anno></c> is a queue and returns <c>true</c> + if so, otherwise <c>false</c>.</p> </desc> </func> + <func> - <name name="out" arity="1"/> - <fsummary>Remove the front item from a queue</fsummary> + <name name="join" arity="2"/> + <fsummary>Join two queues.</fsummary> <desc> - <p>Removes the item at the front of queue <c><anno>Q1</anno></c>. Returns the - tuple <c>{{value, <anno>Item</anno>}, <anno>Q2</anno>}</c>, where <c><anno>Item</anno></c> is the - item removed and <c><anno>Q2</anno></c> is the resulting queue. If <c><anno>Q1</anno></c> is - empty, the tuple <c>{empty, <anno>Q1</anno>}</c> is returned.</p> + <p>Returns a queue <c><anno>Q3</anno></c> that is the result of joining + <c><anno>Q1</anno></c> and <c><anno>Q2</anno></c> with + <c><anno>Q1</anno></c> in front of <c><anno>Q2</anno></c>.</p> </desc> </func> + <func> - <name name="out_r" arity="1"/> - <fsummary>Remove the rear item from a queue</fsummary> + <name name="len" arity="1"/> + <fsummary>Get the length of a queue.</fsummary> <desc> - <p>Removes the item at the rear of the queue <c><anno>Q1</anno></c>. Returns the - tuple <c>{{value, <anno>Item</anno>}, <anno>Q2</anno>}</c>, where <c><anno>Item</anno></c> is the - item removed and <c><anno>Q2</anno></c> is the new queue. If <c><anno>Q1</anno></c> is - empty, the tuple <c>{empty, <anno>Q1</anno>}</c> is returned. </p> + <p>Calculates and returns the length of queue <c><anno>Q</anno></c>.</p> </desc> </func> <func> - <name name="from_list" arity="1"/> - <fsummary>Convert a list to a queue</fsummary> + <name name="member" arity="2"/> + <fsummary>Test if an item is in a queue.</fsummary> <desc> - <p>Returns a queue containing the items in <c><anno>L</anno></c> in the - same order; the head item of the list will become the front - item of the queue.</p> + <p>Returns <c>true</c> if <c><anno>Item</anno></c> matches some element + in <c><anno>Q</anno></c>, otherwise <c>false</c>.</p> </desc> </func> + <func> - <name name="to_list" arity="1"/> - <fsummary>Convert a queue to a list</fsummary> + <name name="new" arity="0"/> + <fsummary>Create an empty queue.</fsummary> <desc> - <p>Returns a list of the items in the queue in the same order; - the front item of the queue will become the head of the list.</p> + <p>Returns an empty queue.</p> </desc> </func> <func> - <name name="reverse" arity="1"/> - <fsummary>Reverse a queue</fsummary> + <name name="out" arity="1"/> + <fsummary>Remove the front item from a queue.</fsummary> <desc> - <p>Returns a queue <c><anno>Q2</anno></c> that contains the items of - <c><anno>Q1</anno></c> in the reverse order.</p> + <p>Removes the item at the front of queue <c><anno>Q1</anno></c>. + Returns tuple <c>{{value, <anno>Item</anno>}, <anno>Q2</anno>}</c>, + where <c><anno>Item</anno></c> is the item removed and + <c><anno>Q2</anno></c> is the resulting queue. If + <c><anno>Q1</anno></c> is empty, tuple + <c>{empty, <anno>Q1</anno>}</c> is returned.</p> </desc> </func> + <func> - <name name="split" arity="2"/> - <fsummary>Split a queue in two</fsummary> + <name name="out_r" arity="1"/> + <fsummary>Remove the rear item from a queue.</fsummary> <desc> - <p>Splits <c><anno>Q1</anno></c> in two. The <c><anno>N</anno></c> front items - are put in <c><anno>Q2</anno></c> and the rest in <c><anno>Q3</anno></c></p> + <p>Removes the item at the rear of queue <c><anno>Q1</anno></c>. + Returns tuple <c>{{value, <anno>Item</anno>}, <anno>Q2</anno>}</c>, + where <c><anno>Item</anno></c> is the item removed and + <c><anno>Q2</anno></c> is the new queue. If <c><anno>Q1</anno></c> is + empty, tuple <c>{empty, <anno>Q1</anno>}</c> is returned.</p> </desc> </func> + <func> - <name name="join" arity="2"/> - <fsummary>Join two queues</fsummary> + <name name="reverse" arity="1"/> + <fsummary>Reverse a queue.</fsummary> <desc> - <p>Returns a queue <c><anno>Q3</anno></c> that is the result of joining - <c><anno>Q1</anno></c> and <c><anno>Q2</anno></c> with <c><anno>Q1</anno></c> in front of - <c><anno>Q2</anno></c>.</p> + <p>Returns a queue <c><anno>Q2</anno></c> containing the items of + <c><anno>Q1</anno></c> in the reverse order.</p> </desc> </func> + <func> - <name name="filter" arity="2"/> - <fsummary>Filter a queue</fsummary> + <name name="split" arity="2"/> + <fsummary>Split a queue in two.</fsummary> <desc> - <p>Returns a queue <c><anno>Q2</anno></c> that is the result of calling - <c><anno>Fun</anno>(<anno>Item</anno>)</c> on all items in <c><anno>Q1</anno></c>, - in order from front to rear.</p> - <p>If <c><anno>Fun</anno>(<anno>Item</anno>)</c> returns <c>true</c>, <c>Item</c> - is copied to the result queue. If it returns <c>false</c>, - <c><anno>Item</anno></c> is not copied. If it returns a list - the list elements are inserted instead of <c>Item</c> in the - result queue.</p> - <p>So, <c><anno>Fun</anno>(<anno>Item</anno>)</c> returning <c>[<anno>Item</anno>]</c> is thereby - semantically equivalent to returning <c>true</c>, just - as returning <c>[]</c> is semantically equivalent to - returning <c>false</c>. But returning a list builds - more garbage than returning an atom.</p> + <p>Splits <c><anno>Q1</anno></c> in two. The <c><anno>N</anno></c> + front items are put in <c><anno>Q2</anno></c> and the rest in + <c><anno>Q3</anno></c>.</p> </desc> </func> + <func> - <name name="member" arity="2"/> - <fsummary>Test if an item is in a queue</fsummary> + <name name="to_list" arity="1"/> + <fsummary>Convert a queue to a list.</fsummary> <desc> - <p>Returns <c>true</c> if <c><anno>Item</anno></c> matches some element - in <c><anno>Q</anno></c>, otherwise <c>false</c>.</p> + <p>Returns a list of the items in the queue in the same order; + the front item of the queue becomes the head of the list.</p> </desc> </func> </funcs> - - <section> <title>Extended API</title> </section> <funcs> <func> - <name name="get" arity="1"/> - <fsummary>Return the front item of a queue</fsummary> - <desc> - <p>Returns <c><anno>Item</anno></c> at the front of queue <c><anno>Q</anno></c>.</p> - <p>Fails with reason <c>empty</c> if <c><anno>Q</anno></c> is empty.</p> - </desc> - </func> - <func> - <name name="get_r" arity="1"/> - <fsummary>Return the rear item of a queue</fsummary> - <desc> - <p>Returns <c><anno>Item</anno></c> at the rear of queue <c><anno>Q</anno></c>.</p> - <p>Fails with reason <c>empty</c> if <c><anno>Q</anno></c> is empty.</p> - </desc> - </func> - <func> <name name="drop" arity="1"/> - <fsummary>Remove the front item from a queue</fsummary> + <fsummary>Remove the front item from a queue.</fsummary> <desc> <p>Returns a queue <c><anno>Q2</anno></c> that is the result of removing the front item from <c><anno>Q1</anno></c>.</p> <p>Fails with reason <c>empty</c> if <c><anno>Q1</anno></c> is empty.</p> </desc> </func> + <func> <name name="drop_r" arity="1"/> - <fsummary>Remove the rear item from a queue</fsummary> + <fsummary>Remove the rear item from a queue.</fsummary> <desc> <p>Returns a queue <c><anno>Q2</anno></c> that is the result of removing the rear item from <c><anno>Q1</anno></c>.</p> <p>Fails with reason <c>empty</c> if <c><anno>Q1</anno></c> is empty.</p> </desc> </func> + + <func> + <name name="get" arity="1"/> + <fsummary>Return the front item of a queue.</fsummary> + <desc> + <p>Returns <c><anno>Item</anno></c> at the front of queue + <c><anno>Q</anno></c>.</p> + <p>Fails with reason <c>empty</c> if <c><anno>Q</anno></c> is empty.</p> + </desc> + </func> + + <func> + <name name="get_r" arity="1"/> + <fsummary>Return the rear item of a queue.</fsummary> + <desc> + <p>Returns <c><anno>Item</anno></c> at the rear of queue + <c><anno>Q</anno></c>.</p> + <p>Fails with reason <c>empty</c> if <c><anno>Q</anno></c> is empty.</p> + </desc> + </func> + <func> <name name="peek" arity="1"/> - <fsummary>Return the front item of a queue</fsummary> + <fsummary>Return the front item of a queue.</fsummary> <desc> - <p>Returns the tuple <c>{value, <anno>Item</anno>}</c> where <c><anno>Item</anno></c> is the - front item of <c><anno>Q</anno></c>, or <c>empty</c> if <c><anno>Q</anno></c> is empty.</p> + <p>Returns tuple <c>{value, <anno>Item</anno>}</c>, where + <c><anno>Item</anno></c> is the front item of <c><anno>Q</anno></c>, + or <c>empty</c> if <c><anno>Q</anno></c> is empty.</p> </desc> </func> + <func> <name name="peek_r" arity="1"/> - <fsummary>Return the rear item of a queue</fsummary> + <fsummary>Return the rear item of a queue.</fsummary> <desc> - <p>Returns the tuple <c>{value, <anno>Item</anno>}</c> where <c><anno>Item</anno></c> is the - rear item of <c><anno>Q</anno></c>, or <c>empty</c> if <c><anno>Q</anno></c> is empty.</p> + <p>Returns tuple <c>{value, <anno>Item</anno>}</c>, where + <c><anno>Item</anno></c> is the rear item of <c><anno>Q</anno></c>, + or <c>empty</c> if <c><anno>Q</anno></c> is empty.</p> </desc> </func> </funcs> - <section> <title>Okasaki API</title> </section> @@ -307,58 +343,92 @@ <funcs> <func> <name name="cons" arity="2"/> - <fsummary>Insert an item at the head of a queue</fsummary> + <fsummary>Insert an item at the head of a queue.</fsummary> <desc> - <p>Inserts <c><anno>Item</anno></c> at the head of queue <c><anno>Q1</anno></c>. Returns + <p>Inserts <c><anno>Item</anno></c> at the head of queue + <c><anno>Q1</anno></c>. Returns the new queue <c><anno>Q2</anno></c>.</p> </desc> </func> + + <func> + <name name="daeh" arity="1"/> + <fsummary>Return the tail item of a queue.</fsummary> + <desc> + <p>Returns the tail item of queue <c><anno>Q</anno></c>.</p> + <p>Fails with reason <c>empty</c> if <c><anno>Q</anno></c> is empty.</p> + </desc> + </func> + <func> <name name="head" arity="1"/> - <fsummary>Return the item at the head of a queue</fsummary> + <fsummary>Return the item at the head of a queue.</fsummary> <desc> - <p>Returns <c><anno>Item</anno></c> from the head of queue <c><anno>Q</anno></c>.</p> + <p>Returns <c><anno>Item</anno></c> from the head of queue + <c><anno>Q</anno></c>.</p> <p>Fails with reason <c>empty</c> if <c><anno>Q</anno></c> is empty.</p> </desc> </func> + <func> - <name name="tail" arity="1"/> - <fsummary>Remove the head item from a queue</fsummary> + <name name="init" arity="1"/> + <fsummary>Remove the tail item from a queue.</fsummary> <desc> <p>Returns a queue <c><anno>Q2</anno></c> that is the result of removing - the head item from <c><anno>Q1</anno></c>.</p> + the tail item from <c><anno>Q1</anno></c>.</p> <p>Fails with reason <c>empty</c> if <c><anno>Q1</anno></c> is empty.</p> </desc> </func> + <func> - <name name="snoc" arity="2"/> - <fsummary>Insert an item at the tail of a queue</fsummary> + <name name="lait" arity="1"/> + <fsummary>Remove the tail item from a queue.</fsummary> <desc> - <p>Inserts <c><anno>Item</anno></c> as the tail item of queue <c><anno>Q1</anno></c>. Returns - the new queue <c><anno>Q2</anno></c>.</p> + <p>Returns a queue <c><anno>Q2</anno></c> that is the result of removing + the tail item from <c><anno>Q1</anno></c>.</p> + <p>Fails with reason <c>empty</c> if <c><anno>Q1</anno></c> is empty.</p> + <p>The name <c>lait/1</c> is a misspelling - do not use it anymore.</p> </desc> </func> + <func> - <name name="daeh" arity="1"/> <name name="last" arity="1"/> - <fsummary>Return the tail item of a queue</fsummary> + <fsummary>Return the tail item of a queue.</fsummary> <desc> <p>Returns the tail item of queue <c><anno>Q</anno></c>.</p> <p>Fails with reason <c>empty</c> if <c><anno>Q</anno></c> is empty.</p> </desc> </func> + <func> <name name="liat" arity="1"/> - <name name="init" arity="1"/> - <name name="lait" arity="1"/> - <fsummary>Remove the tail item from a queue</fsummary> + <fsummary>Remove the tail item from a queue.</fsummary> <desc> <p>Returns a queue <c><anno>Q2</anno></c> that is the result of removing the tail item from <c><anno>Q1</anno></c>.</p> <p>Fails with reason <c>empty</c> if <c><anno>Q1</anno></c> is empty.</p> - <p>The name <c>lait/1</c> is a misspelling - do not use it anymore.</p> </desc> </func> - </funcs> + <func> + <name name="snoc" arity="2"/> + <fsummary>Insert an item at the tail of a queue.</fsummary> + <desc> + <p>Inserts <c><anno>Item</anno></c> as the tail item of queue + <c><anno>Q1</anno></c>. Returns + the new queue <c><anno>Q2</anno></c>.</p> + </desc> + </func> + + <func> + <name name="tail" arity="1"/> + <fsummary>Remove the head item from a queue.</fsummary> + <desc> + <p>Returns a queue <c><anno>Q2</anno></c> that is the result of removing + the head item from <c><anno>Q1</anno></c>.</p> + <p>Fails with reason <c>empty</c> if <c><anno>Q1</anno></c> is empty.</p> + </desc> + </func> + </funcs> </erlref> + |