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Commit 88fb78d

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Merge pull request #40 from justinmeiners/39-list-examples
add example of how to use list pool
2 parents 1779640 + 88c67b1 commit 88fb78d

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7 files changed

+102
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‎08_lisp.html

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}
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</code></pre>
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<p><strong>Exercise:</strong> Before moving on, get familiar with these operations.
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Create a simple list inside a pool and print it by iterating through its contents
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(solved in <code>test_list_pool.cpp</code> at the end of the chapter).</p>
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<a name="List-queue"></a>
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<h2>List queue</h2>
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pair_type empty_queue() { return pair_type(end(), end()); }
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</code></pre>
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<p>You can remove an element from the front of the queue:</p>
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<pre><code>pair_type pop_front(const pair_type&amp; p) {
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if (empty(p)) return p;
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return pair_type(next(p.first), p.second);
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}
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</code></pre>
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<p>You can add an element to the front, or the back of the queue:</p>
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<pre><code>pair_type push_front(const pair_type&amp; p, const T&amp; value) {
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}
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</code></pre>
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<p>You can remove an element from the front of the queue<sup id="fnref:9"><a href="#fn:9" rel="footnote">9</a></sup>:</p>
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<pre><code>pair_type pop_front(const pair_type&amp; p) {
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if (empty(p)) return p;
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return pair_type(next(p.first), p.second);
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}
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</code></pre>
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<p>Now we can also free lists in constant time,
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simply by attaching the end of our list to the free list.</p>
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<ul>
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<li><a href="code/list_pool.h">list_pool.h</a></li>
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<li><a href="code/list_pool_iterator.h">list_pool_iterator.h</a> (included by <code>list_pool.h</code>, but not discussed until Chapter 9)</li>
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<li><a href="code/test_list_pool.cpp">test_list_pool.cpp</a></li>
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</ul>
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<div class="footnotes">
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<li id="fn:8">
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The assignment in this code is the same as <code>(setf (cdr x) free-list)</code> in Common Lisp,
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or <code>(set-cdr! x free-list)</code> in Scheme.<a href="#fnref:8" rev="footnote">&#8617;</a></li>
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<li id="fn:9">
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Since we implement <code>pop_front</code>, you might also expect <code>pop_back</code>.
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A little thought will reveal there is no constant
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time implementation for singly linked lists.
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The queue has a reference to the last node in the queue,
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but removing it would require modification
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of the preceding node.<a href="#fnref:9" rev="footnote">&#8617;</a></li>
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</ol>
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</div>
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‎08_lisp.md

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while (!pool.is_empty(x)) x = pool.free(x);
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}
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**Exercise:** Before moving on, get familiar with these operations.
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Create a simple list inside a pool and print it by iterating through its contents
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(solved in `test_list_pool.cpp` at the end of the chapter).
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[^rplaca-explanation]: `rplaca` and `rplacd` are unfriendly abbrevations of
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"replace car" and "replace cdr" (see "Lisp 1.5 Programmer's Manual").
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bool empty(const pair_type& p) { return is_end(p.first); }
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pair_type empty_queue() { return pair_type(end(), end()); }
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You can remove an element from the front of the queue:
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pair_type pop_front(const pair_type& p) {
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if (empty(p)) return p;
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return pair_type(next(p.first), p.second);
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}
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You can add an element to the front, or the back of the queue:
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pair_type push_front(const pair_type& p, const T& value) {
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return pair_type(p.first, new_node);
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}
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You can remove an element from the front of the queue[^no-pop-back]:
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pair_type pop_front(const pair_type& p) {
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if (empty(p)) return p;
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return pair_type(next(p.first), p.second);
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}
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Now we can also free lists in constant time,
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simply by attaching the end of our list to the free list.
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void free(const pair_type& p) { free(p.first, p.second); }
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[^no-pop-back]: Since we implement `pop_front`, you might also expect `pop_back`.
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A little thought will reveal there is no constant
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time implementation for singly linked lists.
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The queue has a reference to the last node in the queue,
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but removing it would require modification
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of the preceding node.
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## Code
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- [list_pool.h](code/list_pool.h)
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- [list_pool_iterator.h](code/list_pool_iterator.h) (included by `list_pool.h`, but not discussed until Chapter 9)
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- [test_list_pool.cpp](code/test_list_pool.cpp)

‎09_iterators.html

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When you took Algebra in grade school,
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they used <code>=</code> and they used <code>x</code> and <code>y</code> and I think it&rsquo;s good.</p>
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<p><strong>Exercise:</strong> Experiment with list pool iterators by using
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a standard library algorithm on them, such as <code>find</code> or <code>copy</code>
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(see <code>test_list_pool_iterator.cpp</code> at the end of the chapter).</p>
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<a name="Thoughts-about-iterator-design"></a>
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<h2>Thoughts about iterator design</h2>
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<ul>
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<li><a href="code/list_pool_iterator.h">list_pool_iterator.h</a></li>
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<li><a href="code/test_list_pool_iterator.cpp">test_list_pool_iterator.cpp</a></li>
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</ul>
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<div class="footnotes">

‎09_iterators.md

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But, oh well.
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When you took Algebra in grade school,
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they used `=` and they used `x` and `y` and I think it's good.
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**Exercise:** Experiment with list pool iterators by using
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a standard library algorithm on them, such as `find` or `copy`
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(see `test_list_pool_iterator.cpp` at the end of the chapter).
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## Thoughts about iterator design
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## Code
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- [list_pool_iterator.h](code/list_pool_iterator.h)
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- [test_list_pool_iterator.cpp](code/test_list_pool_iterator.cpp)

‎code/index.html

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‎code/test_list_pool.cpp

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#include <iostream>
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#include <stdint.h>
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#include "list_pool.h"
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int main() {
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typedef typename list_pool<char, uint16_t>::list_type L;
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list_pool<char, uint16_t> pool;
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// Create a list "a b c",
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// same as Lisp (cons a (cons b (cons c '()))).
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L l = pool.end();
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l = pool.allocate('c', l);
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l = pool.allocate('b', l);
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l = pool.allocate('a', l);
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// Print contents of list.
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L current = l;
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while (current != pool.end()) {
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std::cout << pool.value(current) << " ";
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current = pool.next(current);
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}
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std::cout << std::endl;
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// Pool will cleanup automatically when out of scope.
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// But, let's go ahead and test free.
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free_list(pool, current);
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}
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‎code/test_list_pool_iterator.cpp

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#include <iostream>
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#include <iterator>
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#include <stdint.h>
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#include "list_pool.h"
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int main() {
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typedef typename list_pool<char, uint16_t>::iterator I;
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list_pool<char, uint16_t> pool;
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// Create a list "a b c",
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// same as Lisp (cons a (cons b (cons c '()))).
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I last(pool);
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I first = last;
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push_front(first, 'c');
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push_front(first, 'b');
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push_front(first, 'a');
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// Print contents of list.
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std::copy(first, last, std::ostream_iterator<char>(std::cout, " "));
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}
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