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<pre id='vimCodeElement'>
<span class="Comment">//: Addresses help us spend less time copying data around.</span>

<span class="Comment">//: So far we've been operating on primitives like numbers and characters, and</span>
<span class="Comment">//: we've started combining these primitives together into larger logical</span>
<span class="Comment">//: units (containers or arrays) that may contain many different primitives at</span>
<span class="Comment">//: once. Containers and arrays can grow quite large in complex programs, and</span>
<span class="Comment">//: we'd like some way to efficiently share them between recipes without</span>
<span class="Comment">//: constantly having to make copies. Right now 'next-ingredient' and 'return'</span>
<span class="Comment">//: copy data across recipe boundaries. To avoid copying large quantities of</span>
<span class="Comment">//: data around, we'll use *addresses*. An address is a bookmark to some</span>
<span class="Comment">//: arbitrary quantity of data (the *payload*). It's a primitive, so it's as</span>
<span class="Comment">//: efficient to copy as a number. To read or modify the payload 'pointed to'</span>
<span class="Comment">//: by an address, we'll perform a *lookup*.</span>
<span class="Comment">//:</span>
<span class="Comment">//: The notion of 'lookup' isn't an instruction like 'add' or 'subtract'.</span>
<span class="Comment">//: Instead it's an operation that can be performed when reading any of the</span>
<span class="Comment">//: ingredients of an instruction, and when writing to any of the products. To</span>
<span class="Comment">//: write to the payload of an ingredient rather than its value, simply add</span>
<span class="Comment">//: the /lookup property to it. Modern computers provide efficient support for</span>
<span class="Comment">//: addresses and lookups, making this a realistic feature.</span>
<span class="Comment">//:</span>
<span class="Comment">//: To recap: an address is a bookmark to some potentially large payload, and</span>
<span class="Comment">//: you can replace any ingredient or product with a lookup to an address of</span>
<span class="Comment">//: the appropriate type. But how do we get addresses to begin with? That</span>
<span class="Comment">//: requires a little more explanation. Once we introduce the notion of</span>
<span class="Comment">//: bookmarks to data, we have to think about the life cycle of a piece of</span>
<span class="Comment">//: data and its bookmarks (because remember, bookmarks can be copied around</span>
<span class="Comment">//: just like anything else). Otherwise several bad outcomes can result (and</span>
<span class="Comment">//: indeed *have* resulted in past languages like C):</span>
<span class="Comment">//:</span>
<span class="Comment">//:   a) You can run out of memory if you don't have a way to reclaim</span>
<span class="Comment">//:   data.</span>
<span class="Comment">//:   b) If you allow data to be reclaimed, you have to be careful not to</span>
<span class="Comment">//:   leave any stale addresses pointing at it. Otherwise your program might</span>
<span class="Comment">//:   try to lookup such an address and find something unexpected. Such</span>
<span class="Comment">//:   problems can be very hard to track down, and they can also be exploited</span>
<span class="Comment">//:   to break into your computer over the network, etc.</span>
<span class="Comment">//:</span>
<span class="Comment">//: To avoid these problems, we introduce the notion of a *reference count* or</span>
<span class="Comment">//: refcount. The life cycle of a bit of data accessed through addresses looks</span>
<span class="Comment">//: like this.</span>
<span class="Comment">//:</span>
<span class="Comment">//:    We create space in computer memory for it using the 'new' instruction.</span>
<span class="Comment">//:    The 'new' instruction takes a type as an ingredient, allocates</span>
<span class="Comment">//:    sufficient space to hold that type, and returns an address (bookmark)</span>
<span class="Comment">//:    to the allocated space.</span>
<span class="Comment">//:</span>
<span class="Comment">//:      x:address:num &lt;- new number:type</span>
<span class="Comment">//:</span>
<span class="Comment">//:                     +------------+</span>
<span class="Comment">//:          x -------&gt; |  number    |</span>
<span class="Comment">//:                     +------------+</span>
<span class="Comment">//:</span>
<span class="Comment">//:    That isn't entirely accurate. Under the hood, 'new' allocates an extra</span>
<span class="Comment">//:    number -- the refcount:</span>
<span class="Comment">//:</span>
<span class="Comment">//:                     +------------+------------+</span>
<span class="Comment">//:          x -------&gt; | refcount   |  number    |</span>
<span class="Comment">//:                     +------------+------------+</span>
<span class="Comment">//:</span>
<span class="Comment">//:    This probably seems like a waste of space. In practice it isn't worth</span>
<span class="Comment">//:    allocating individual numbers and our payload will tend to be larger,</span>
<span class="Comment">//:    so the picture would look more like this (zooming out a bit):</span>
<span class="Comment">//:</span>
<span class="Comment">//:                         +-------------------------+</span>
<span class="Comment">//:                     +---+                         |</span>
<span class="Comment">//:          x -------&gt; | r |                         |</span>
<span class="Comment">//:                     +---+        DATA             |</span>
<span class="Comment">//:                         |                         |</span>
<span class="Comment">//:                         |                         |</span>
<span class="Comment">//:                         +-------------------------+</span>
<span class="Comment">//:</span>
<span class="Comment">//:    (Here 'r' denotes the refcount. It occupies a tiny amount of space</span>
<span class="Comment">//:    compared to the payload.)</span>
<span class="Comment">//:</span>
<span class="Comment">//:    Anyways, back to our example where the data is just a single number.</span>
<span class="Comment">//:    After the call to 'new', Mu's map of memory looks like this:</span>
<span class="Comment">//:</span>
<span class="Comment">//:                     +---+------------+</span>
<span class="Comment">//:          x -------&gt; | 1 |  number    |</span>
<span class="Comment">//:                     +---+------------+</span>
<span class="Comment">//:</span>
<span class="Comment">//:    The refcount of 1 here indicates that this number has one bookmark</span>
<span class="Comment">//:    outstanding. If you then make a copy of x, the refcount increments:</span>
<span class="Comment">//:</span>
<span class="Comment">//:      y:address:num &lt;- copy x</span>
<span class="Comment">//:</span>
<span class="Comment">//:          x ---+     +---+------------+</span>
<span class="Comment">//:               +---&gt; | 2 |  number    |</span>
<span class="Comment">//:          y ---+     +---+------------+</span>
<span class="Comment">//:</span>
<span class="Comment">//:    Whether you access the payload through x or y, Mu knows how many</span>
<span class="Comment">//:    bookmarks are outstanding to it. When you change x or y, the refcount</span>
<span class="Comment">//:    transparently decrements:</span>
<span class="Comment">//:</span>
<span class="Comment">//:      x &lt;- copy 0  # an address is just a number, you can always write 0 to it</span>
<span class="Comment">//:</span>
<span class="Comment">//:                     +---+------------+</span>
<span class="Comment">//:          y -------&gt; | 1 |  number    |</span>
<span class="Comment">//:                     +---+------------+</span>
<span class="Comment">//:</span>
<span class="Comment">//:    The final flourish is what happens when the refcount goes down to 0: Mu</span>
<span class="Comment">//:    reclaims the space occupied by both refcount and payload in memory, and</span>
<span class="Comment">//:    they're ready to be reused by later calls to 'new'.</span>
<span class="Comment">//:</span>
<span class="Comment">//:      y &lt;- copy 0</span>
<span class="Comment">//:</span>
<span class="Comment">//:                     +---+------------+</span>
<span class="Comment">//:                     | 0 |  XXXXXXX   |</span>
<span class="Comment">//:                     +---+------------+</span>
<span class="Comment">//:</span>
<span class="Comment">//: Using refcounts fixes both our problems a) and b) above: you can use</span>
<span class="Comment">//: memory for many different purposes as many times as you want without</span>
<span class="Comment">//: running out of memory, and you don't have to worry about ever leaving a</span>
<span class="Comment">//: dangling bookmark when you reclaim memory.</span>
<span class="Comment">//:</span>
<span class="Comment">//: This layer implements creating addresses using 'new'. The next few layers</span>
<span class="Comment">//: will flesh out the rest of the life cycle.</span>

<span class="Comment">//: todo: give 'new' a custodian ingredient. Following malloc/free is a temporary hack.</span>

<span class="Delimiter">:(scenario new)</span>
<span class="Comment"># call 'new' two times with identical types without modifying the results; you</span>
<span class="Comment"># should get back different results</span>
<span class="muRecipe">def</span> main [
  <span class="Constant">1</span>:address:num/<span class="Special">raw &lt;- </span><span class="Normal">new</span> <span class="Constant">number:type</span>
  <span class="Constant">2</span>:address:num/<span class="Special">raw &lt;- </span><span class="Normal">new</span> <span class="Constant">number:type</span>
  <span class="Constant">3</span>:<span class="Normal">bool</span>/<span class="Special">raw &lt;- </span>equal <span class="Constant">1</span>:address:num/<span class="Special">raw</span><span class="Delimiter">,</span> <span class="Constant">2</span>:address:num/<span class="Special">raw</span>
]
<span class="traceContains">+mem: storing 0 in location 3</span>

<span class="Delimiter">:(scenario new_array)</span>
<span class="Comment"># call 'new' with a second ingredient to allocate an array of some type rather than a single copy</span>
<span class="muRecipe">def</span> main [
  <span class="Constant">1</span>:address:array:num/<span class="Special">raw &lt;- </span><span class="Normal">new</span> <span class="Constant">number:type</span><span class="Delimiter">,</span> <span class="Constant">5</span>
  <span class="Constant">2</span>:address:num/<span class="Special">raw &lt;- </span><span class="Normal">new</span> <span class="Constant">number:type</span>
  <span class="Constant">3</span>:num/<span class="Special">raw &lt;- </span>subtract <span class="Constant">2</span>:address:num/<span class="Special">raw</span><span class="Delimiter">,</span> <span class="Constant">1</span>:address:array:num/<span class="Special">raw</span>
]
<span class="traceContains">+run: {1: (&quot;address&quot; &quot;array&quot; &quot;number&quot;), &quot;raw&quot;: ()} &lt;- new {number: &quot;type&quot;}, {5: &quot;literal&quot;}</span>
<span class="traceContains">+mem: array length is 5</span>
<span class="Comment"># don't forget the extra location for array length, and the second extra location for the refcount</span>
<span class="traceContains">+mem: storing 7 in location 3</span>

<span class="Delimiter">:(scenario dilated_reagent_with_new)</span>
<span class="muRecipe">def</span> main [
  <span class="Constant">1</span>:address:address:num<span class="Special"> &lt;- </span><span class="Normal">new</span> <span class="Delimiter">{(</span>address number<span class="Delimiter">)</span>: type<span class="Delimiter">}</span>
]
<span class="traceContains">+new: size of '(address number)' is 1</span>

<span class="Comment">//: 'new' takes a weird 'type' as its first ingredient; don't error on it</span>
<span class="Delimiter">:(before &quot;End Mu Types Initialization&quot;)</span>
put<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;type&quot;</span><span class="Delimiter">,</span> <span class="Constant">0</span><span class="Delimiter">);</span>
<span class="Delimiter">:(code)</span>
<span class="Normal">bool</span> is_mu_type_literal<span class="Delimiter">(</span><span class="Normal">const</span> reagent&amp; r<span class="Delimiter">)</span> <span class="Delimiter">{</span>
  <span class="Identifier">return</span> is_literal<span class="Delimiter">(</span>r<span class="Delimiter">)</span> &amp;&amp; r<span class="Delimiter">.</span>type &amp;&amp; r<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>name == <span class="Constant">&quot;type&quot;</span><span class="Delimiter">;</span>
<span class="Delimiter">}</span>

<span class="Delimiter">:(before &quot;End Primitive Recipe Declarations&quot;)</span>
NEW<span class="Delimiter">,</span>
<span class="Delimiter">:(before &quot;End Primitive Recipe Numbers&quot;)</span>
put<span class="Delimiter">(</span>Recipe_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;new&quot;</span><span class="Delimiter">,</span> NEW<span class="Delimiter">);</span>
<span class="Delimiter">:(before &quot;End Primitive Recipe Checks&quot;)</span>
<span class="Normal">case</span> NEW: <span class="Delimiter">{</span>
  <span class="Normal">const</span> recipe&amp; caller = get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">);</span>
  <span class="Normal">if</span> <span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>empty<span class="Delimiter">()</span> || SIZE<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">)</span> &gt; <span class="Constant">2</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
    raise &lt;&lt; maybe<span class="Delimiter">(</span>caller<span class="Delimiter">.</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;'new' requires one or two ingredients, but got '&quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>original_string &lt;&lt; <span class="Constant">&quot;'</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
    <span class="Identifier">break</span><span class="Delimiter">;</span>
  <span class="Delimiter">}</span>
  <span class="Comment">// End NEW Check Special-cases</span>
  <span class="Normal">const</span> reagent&amp; type = inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>
  <span class="Normal">if</span> <span class="Delimiter">(</span>!is_mu_type_literal<span class="Delimiter">(</span>type<span class="Delimiter">))</span> <span class="Delimiter">{</span>
    raise &lt;&lt; maybe<span class="Delimiter">(</span>caller<span class="Delimiter">.</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;first ingredient of 'new' should be a type, but got '&quot;</span> &lt;&lt; type<span class="Delimiter">.</span>original_string &lt;&lt; <span class="Constant">&quot;'</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
    <span class="Identifier">break</span><span class="Delimiter">;</span>
  <span class="Delimiter">}</span>
  <span class="Normal">if</span> <span class="Delimiter">(</span>SIZE<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">)</span> &gt; <span class="Constant">1</span> &amp;&amp; !is_mu_number<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">)))</span> <span class="Delimiter">{</span>
    raise &lt;&lt; maybe<span class="Delimiter">(</span>caller<span class="Delimiter">.</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;second ingredient of 'new' should be a number (array length), but got '&quot;</span> &lt;&lt; type<span class="Delimiter">.</span>original_string &lt;&lt; <span class="Constant">&quot;'</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
    <span class="Identifier">break</span><span class="Delimiter">;</span>
  <span class="Delimiter">}</span>
  <span class="Normal">if</span> <span class="Delimiter">(</span>inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>empty<span class="Delimiter">())</span> <span class="Delimiter">{</span>
    raise &lt;&lt; maybe<span class="Delimiter">(</span>caller<span class="Delimiter">.</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;result of 'new' should never be ignored</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
    <span class="Identifier">break</span><span class="Delimiter">;</span>
  <span class="Delimiter">}</span>
  <span class="Normal">if</span> <span class="Delimiter">(</span>!product_of_new_is_valid<span class="Delimiter">(</span>inst<span class="Delimiter">))</span> <span class="Delimiter">{</span>
    raise &lt;&lt; maybe<span class="Delimiter">(</span>caller<span class="Delimiter">.</span>name<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;product of 'new' has incorrect type: '&quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>original_string &lt;&lt; <span class="Constant">&quot;'</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
    <span class="Identifier">break</span><span class="Delimiter">;</span>
  <span class="Delimiter">}</span>
  <span class="Identifier">break</span><span class="Delimiter">;</span>
<span class="Delimiter">}</span>
<span class="Delimiter">:(code)</span>
<span class="Normal">bool</span> product_of_new_is_valid<span class="Delimiter">(</span><span class="Normal">const</span> instruction&amp; inst<span class="Delimiter">)</span> <span class="Delimiter">{</span>
  reagent<span class="Comment">/*</span><span class="Comment">copy</span><span class="Comment">*/</span> product = inst<span class="Delimiter">.</span>products<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>
  <span class="Comment">// Update NEW product in Check</span>
  <span class="Normal">if</span> <span class="Delimiter">(</span>!product<span class="Delimiter">.</span>type || product<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>atom || product<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>left<span class="Delimiter">-&gt;</span>value != get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;address&quot;</span><span class="Delimiter">))</span>
    <span class="Identifier">return</span> <span class="Constant">false</span><span class="Delimiter">;</span>
  drop_from_type<span class="Delimiter">(</span>product<span class="Delimiter">,</span> <span class="Constant">&quot;address&quot;</span><span class="Delimiter">);</span>
  <span class="Normal">if</span> <span class="Delimiter">(</span>SIZE<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">)</span> &gt; <span class="Constant">1</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
    <span class="Comment">// array allocation</span>
    <span class="Normal">if</span> <span class="Delimiter">(</span>!product<span class="Delimiter">.</span>type || product<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>atom || product<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>left<span class="Delimiter">-&gt;</span>value != get<span class="Delimiter">(</span>Type_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;array&quot;</span><span class="Delimiter">))</span>
      <span class="Identifier">return</span> <span class="Constant">false</span><span class="Delimiter">;</span>
    drop_from_type<span class="Delimiter">(</span>product<span class="Delimiter">,</span> <span class="Constant">&quot;array&quot;</span><span class="Delimiter">);</span>
  <span class="Delimiter">}</span>
  reagent<span class="Comment">/*</span><span class="Comment">local</span><span class="Comment">*/</span> expected_product<span class="Delimiter">;</span>
  expected_product<span class="Delimiter">.</span>type = new_type_tree<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>name<span class="Delimiter">);</span>
  <span class="Identifier">return</span> types_strictly_match<span class="Delimiter">(</span>product<span class="Delimiter">,</span> expected_product<span class="Delimiter">);</span>
<span class="Delimiter">}</span>

<span class="Normal">void</span> drop_from_type<span class="Delimiter">(</span>reagent&amp; r<span class="Delimiter">,</span> string expected_type<span class="Delimiter">)</span> <span class="Delimiter">{</span>
  assert<span class="Delimiter">(</span>!r<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>atom<span class="Delimiter">);</span>
  <span class="Normal">if</span> <span class="Delimiter">(</span>r<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>left<span class="Delimiter">-&gt;</span>name != expected_type<span class="Delimiter">)</span> <span class="Delimiter">{</span>
    raise &lt;&lt; <span class="Constant">&quot;can't drop2 &quot;</span> &lt;&lt; expected_type &lt;&lt; <span class="Constant">&quot; from '&quot;</span> &lt;&lt; to_string<span class="Delimiter">(</span>r<span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;'</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
    <span class="Identifier">return</span><span class="Delimiter">;</span>
  <span class="Delimiter">}</span>
  <span class="Comment">// r.type = r.type-&gt;right</span>
  type_tree* tmp = r<span class="Delimiter">.</span>type<span class="Delimiter">;</span>
  r<span class="Delimiter">.</span>type = tmp<span class="Delimiter">-&gt;</span>right<span class="Delimiter">;</span>
  tmp<span class="Delimiter">-&gt;</span>right = <span class="Constant">NULL</span><span class="Delimiter">;</span>
  <span class="Normal">delete</span> tmp<span class="Delimiter">;</span>
  <span class="Comment">// if (!r.type-&gt;right) r.type = r.type-&gt;left</span>
  assert<span class="Delimiter">(</span>!r<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>atom<span class="Delimiter">);</span>
  <span class="Normal">if</span> <span class="Delimiter">(</span>r<span class="Delimiter">.</span>type<span class="Delimiter">-&gt;</span>right<span class="Delimiter">)</span> <span class="Identifier">return</span><span class="Delimiter">;</span>
  tmp = r<span class="Delimiter">.</span>type<span class="Delimiter">;</span>
  r<span class="Delimiter">.</span>type = tmp<span class="Delimiter">-&gt;</span>left<span class="Delimiter">;</span>
  tmp<span class="Delimiter">-&gt;</span>left = <span class="Constant">NULL</span><span class="Delimiter">;</span>
  <span class="Normal">delete</span> tmp<span class="Delimiter">;</span>
<span class="Delimiter">}</span>

<span class="Delimiter">:(scenario new_returns_incorrect_type)</span>
<span class="Special">% Hide_errors = true;</span>
<span class="muRecipe">def</span> main [
  <span class="Constant">1</span>:<span class="Normal">bool</span><span class="Special"> &lt;- </span><span class="Normal">new</span> <span class="Constant">num:type</span>
]
<span class="traceContains">+error: main: product of 'new' has incorrect type: '1:bool &lt;- new num:type'</span>

<span class="Delimiter">:(scenario new_discerns_singleton_list_from_atom_container)</span>
<span class="Special">% Hide_errors = true;</span>
<span class="muRecipe">def</span> main [
  <span class="Constant">1</span>:address:num/<span class="Special">raw &lt;- </span><span class="Normal">new</span> <span class="Delimiter">{(</span>num<span class="Delimiter">)</span>: type<span class="Delimiter">}</span>  <span class="Comment"># should be '{num: type}'</span>
]
<span class="traceContains">+error: main: product of 'new' has incorrect type: '1:address:num/raw &lt;- new {(num): type}'</span>

<span class="Delimiter">:(scenario new_with_type_abbreviation)</span>
<span class="muRecipe">def</span> main [
  <span class="Constant">1</span>:address:num/<span class="Special">raw &lt;- </span><span class="Normal">new</span> <span class="Constant">num:type</span>
]
$error: <span class="Constant">0</span>

<span class="Delimiter">:(scenario new_with_type_abbreviation_inside_compound)</span>
<span class="muRecipe">def</span> main [
  <span class="Delimiter">{</span><span class="Constant">1</span>: <span class="Delimiter">(</span>address address number<span class="Delimiter">),</span> <span class="Special">raw</span>: <span class="Delimiter">()}</span><span class="Special"> &lt;- </span><span class="Normal">new</span> <span class="Delimiter">{(</span>&amp; num<span class="Delimiter">)</span>: type<span class="Delimiter">}</span>
]
$error: <span class="Constant">0</span>

<span class="Comment">//: To implement 'new', a Mu transform turns all 'new' instructions into</span>
<span class="Comment">//: 'allocate' instructions that precompute the amount of memory they want to</span>
<span class="Comment">//: allocate.</span>

<span class="Comment">//: Ensure that we never call 'allocate' directly, and that there's no 'new'</span>
<span class="Comment">//: instructions left after the transforms have run.</span>
<span class="Delimiter">:(before &quot;End Primitive Recipe Checks&quot;)</span>
<span class="Normal">case</span> ALLOCATE: <span class="Delimiter">{</span>
  raise &lt;&lt; <span class="Constant">&quot;never call 'allocate' directly'; always use 'new'</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
  <span class="Identifier">break</span><span class="Delimiter">;</span>
<span class="Delimiter">}</span>
<span class="Delimiter">:(before &quot;End Primitive Recipe Implementations&quot;)</span>
<span class="Normal">case</span> NEW: <span class="Delimiter">{</span>
  raise &lt;&lt; <span class="Constant">&quot;no implementation for 'new'; why wasn't it translated to 'allocate'? Please save a copy of your program and send it to Kartik.</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span> &lt;&lt; end<span class="Delimiter">();</span>
  <span class="Identifier">break</span><span class="Delimiter">;</span>
<span class="Delimiter">}</span>

<span class="Delimiter">:(after &quot;Transform.push_back(check_instruction)&quot;)</span>  <span class="Comment">// check_instruction will guard against direct 'allocate' instructions below</span>
Transform<span class="Delimiter">.</span>push_back<span class="Delimiter">(</span>transform_new_to_allocate<span class="Delimiter">);</span>  <span class="Comment">// idempotent</span>

<span class="Delimiter">:(code)</span>
<span class="Normal">void</span> transform_new_to_allocate<span class="Delimiter">(</span><span class="Normal">const</span> recipe_ordinal r<span class="Delimiter">)</span> <span class="Delimiter">{</span>
  trace<span class="Delimiter">(</span><span class="Constant">9991</span><span class="Delimiter">,</span> <span class="Constant">&quot;transform&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;--- convert 'new' to 'allocate' for recipe &quot;</span> &lt;&lt; get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">).</span>name &lt;&lt; end<span class="Delimiter">();</span>
  <span class="Normal">for</span> <span class="Delimiter">(</span><span class="Normal">int</span> i = <span class="Constant">0</span><span class="Delimiter">;</span>  i &lt; SIZE<span class="Delimiter">(</span>get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">).</span>steps<span class="Delimiter">);</span>  ++i<span class="Delimiter">)</span> <span class="Delimiter">{</span>
    instruction&amp; inst = get<span class="Delimiter">(</span>Recipe<span class="Delimiter">,</span> r<span class="Delimiter">).</span>steps<span class="Delimiter">.</span>at<span class="Delimiter">(</span>i<span class="Delimiter">);</span>
    <span class="Comment">// Convert 'new' To 'allocate'</span>
    <span class="Normal">if</span> <span class="Delimiter">(</span>inst<span class="Delimiter">.</span>name == <span class="Constant">&quot;new&quot;</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
      inst<span class="Delimiter">.</span>operation = ALLOCATE<span class="Delimiter">;</span>
      type_tree* type = new_type_tree<span class="Delimiter">(</span>inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>name<span class="Delimiter">);</span>
      inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>set_value<span class="Delimiter">(</span>size_of<span class="Delimiter">(</span>type<span class="Delimiter">));</span>
      trace<span class="Delimiter">(</span><span class="Constant">9992</span><span class="Delimiter">,</span> <span class="Constant">&quot;new&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;size of '&quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>name &lt;&lt; <span class="Constant">&quot;' is &quot;</span> &lt;&lt; inst<span class="Delimiter">.</span>ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>value &lt;&lt; end<span class="Delimiter">();</span>
      <span class="Normal">delete</span> type<span class="Delimiter">;</span>
    <span class="Delimiter">}</span>
  <span class="Delimiter">}</span>
<span class="Delimiter">}</span>

<span class="Comment">//: implement 'allocate' based on size</span>

<span class="Delimiter">:(before &quot;End Globals&quot;)</span>
<span class="Normal">extern</span> <span class="Normal">const</span> <span class="Normal">int</span> Reserved_for_tests = <span class="Constant">1000</span><span class="Delimiter">;</span>
<span class="Normal">int</span> Memory_allocated_until = Reserved_for_tests<span class="Delimiter">;</span>
<span class="Normal">int</span> Initial_memory_per_routine = <span class="Constant">100000</span><span class="Delimiter">;</span>
<span class="Delimiter">:(before &quot;End Setup&quot;)</span>
Memory_allocated_until = Reserved_for_tests<span class="Delimiter">;</span>
Initial_memory_per_routine = <span class="Constant">100000</span><span class="Delimiter">;</span>
<span class="Delimiter">:(before &quot;End routine Fields&quot;)</span>
<span class="Normal">int</span> alloc<span class="Delimiter">,</span> alloc_max<span class="Delimiter">;</span>
<span class="Delimiter">:(before &quot;End routine Constructor&quot;)</span>
alloc = Memory_allocated_until<span class="Delimiter">;</span>
Memory_allocated_until += Initial_memory_per_routine<span class="Delimiter">;</span>
alloc_max = Memory_allocated_until<span class="Delimiter">;</span>
trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;new&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;routine allocated memory from &quot;</span> &lt;&lt; alloc &lt;&lt; <span class="Constant">&quot; to &quot;</span> &lt;&lt; alloc_max &lt;&lt; end<span class="Delimiter">();</span>

<span class="Delimiter">:(before &quot;End Primitive Recipe Declarations&quot;)</span>
ALLOCATE<span class="Delimiter">,</span>
<span class="Delimiter">:(before &quot;End Primitive Recipe Numbers&quot;)</span>
put<span class="Delimiter">(</span>Recipe_ordinal<span class="Delimiter">,</span> <span class="Constant">&quot;allocate&quot;</span><span class="Delimiter">,</span> ALLOCATE<span class="Delimiter">);</span>
<span class="Delimiter">:(before &quot;End Primitive Recipe Implementations&quot;)</span>
<span class="Normal">case</span> ALLOCATE: <span class="Delimiter">{</span>
  <span class="Comment">// compute the space we need</span>
  <span class="Normal">int</span> size = ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>
  <span class="Normal">if</span> <span class="Delimiter">(</span>SIZE<span class="Delimiter">(</span>ingredients<span class="Delimiter">)</span> &gt; <span class="Constant">1</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
    <span class="Comment">// array allocation</span>
    trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;mem&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;array length is &quot;</span> &lt;&lt; ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">).</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">)</span> &lt;&lt; end<span class="Delimiter">();</span>
    size = <span class="Comment">/*</span><span class="Comment">space for length</span><span class="Comment">*/</span><span class="Constant">1</span> + size*ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">).</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>
  <span class="Delimiter">}</span>
  <span class="Normal">int</span> result = allocate<span class="Delimiter">(</span>size<span class="Delimiter">);</span>
  <span class="Normal">if</span> <span class="Delimiter">(</span>SIZE<span class="Delimiter">(</span>current_instruction<span class="Delimiter">().</span>ingredients<span class="Delimiter">)</span> &gt; <span class="Constant">1</span><span class="Delimiter">)</span> <span class="Delimiter">{</span>
    <span class="Comment">// initialize array length</span>
    trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;mem&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;storing &quot;</span> &lt;&lt; ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">).</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot; in location &quot;</span> &lt;&lt; result+<span class="Comment">/*</span><span class="Comment">skip refcount</span><span class="Comment">*/</span><span class="Constant">1</span> &lt;&lt; end<span class="Delimiter">();</span>
    put<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> result+<span class="Comment">/*</span><span class="Comment">skip refcount</span><span class="Comment">*/</span><span class="Constant">1</span><span class="Delimiter">,</span> ingredients<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">).</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">));</span>
  <span class="Delimiter">}</span>
  products<span class="Delimiter">.</span>resize<span class="Delimiter">(</span><span class="Constant">1</span><span class="Delimiter">);</span>
  products<span class="Delimiter">.</span>at<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">).</span>push_back<span class="Delimiter">(</span>result<span class="Delimiter">);</span>
  <span class="Identifier">break</span><span class="Delimiter">;</span>
<span class="Delimiter">}</span>
<span class="Delimiter">:(code)</span>
<span class="Normal">int</span> allocate<span class="Delimiter">(</span><span class="Normal">int</span> size<span class="Delimiter">)</span> <span class="Delimiter">{</span>
  <span class="Comment">// include space for refcount</span>
  ++size<span class="Delimiter">;</span>
  trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;mem&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;allocating size &quot;</span> &lt;&lt; size &lt;&lt; end<span class="Delimiter">();</span>
<span class="CommentedCode">//?   Total_alloc += size;</span>
<span class="CommentedCode">//?   ++Num_alloc;</span>
  <span class="Comment">// Allocate Special-cases</span>
  <span class="Comment">// compute the region of memory to return</span>
  <span class="Comment">// really crappy at the moment</span>
  ensure_space<span class="Delimiter">(</span>size<span class="Delimiter">);</span>
  <span class="Normal">const</span> <span class="Normal">int</span> result = Current_routine<span class="Delimiter">-&gt;</span>alloc<span class="Delimiter">;</span>
  trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;mem&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;new alloc: &quot;</span> &lt;&lt; result &lt;&lt; end<span class="Delimiter">();</span>
  <span class="Comment">// initialize allocated space</span>
  <span class="Normal">for</span> <span class="Delimiter">(</span><span class="Normal">int</span> address = result<span class="Delimiter">;</span>  address &lt; result+size<span class="Delimiter">;</span>  ++address<span class="Delimiter">)</span> <span class="Delimiter">{</span>
    trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;mem&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;storing 0 in location &quot;</span> &lt;&lt; address &lt;&lt; end<span class="Delimiter">();</span>
    put<span class="Delimiter">(</span>Memory<span class="Delimiter">,</span> address<span class="Delimiter">,</span> <span class="Constant">0</span><span class="Delimiter">);</span>
  <span class="Delimiter">}</span>
  Current_routine<span class="Delimiter">-&gt;</span>alloc += size<span class="Delimiter">;</span>
  <span class="Comment">// no support yet for reclaiming memory between routines</span>
  assert<span class="Delimiter">(</span>Current_routine<span class="Delimiter">-&gt;</span>alloc &lt;= Current_routine<span class="Delimiter">-&gt;</span>alloc_max<span class="Delimiter">);</span>
  <span class="Identifier">return</span> result<span class="Delimiter">;</span>
<span class="Delimiter">}</span>

<span class="Comment">//: statistics for debugging</span>
<span class="CommentedCode">//? :(before &quot;End Globals&quot;)</span>
<span class="CommentedCode">//? int Total_alloc = 0;</span>
<span class="CommentedCode">//? int Num_alloc = 0;</span>
<span class="CommentedCode">//? int Total_free = 0;</span>
<span class="CommentedCode">//? int Num_free = 0;</span>
<span class="CommentedCode">//? :(before &quot;End Setup&quot;)</span>
<span class="CommentedCode">//? Total_alloc = Num_alloc = Total_free = Num_free = 0;</span>
<span class="CommentedCode">//? :(before &quot;End Teardown&quot;)</span>
<span class="CommentedCode">//? cerr &lt;&lt; Total_alloc &lt;&lt; &quot;/&quot; &lt;&lt; Num_alloc</span>
<span class="CommentedCode">//?      &lt;&lt; &quot; vs &quot; &lt;&lt; Total_free &lt;&lt; &quot;/&quot; &lt;&lt; Num_free &lt;&lt; '\n';</span>
<span class="CommentedCode">//? cerr &lt;&lt; SIZE(Memory) &lt;&lt; '\n';</span>

<span class="Delimiter">:(code)</span>
<span class="Normal">void</span> ensure_space<span class="Delimiter">(</span><span class="Normal">int</span> size<span class="Delimiter">)</span> <span class="Delimiter">{</span>
  <span class="Normal">if</span> <span class="Delimiter">(</span>size &gt; Initial_memory_per_routine<span class="Delimiter">)</span> <span class="Delimiter">{</span>
    tb_shutdown<span class="Delimiter">();</span>
    cerr &lt;&lt; <span class="Constant">&quot;can't allocate &quot;</span> &lt;&lt; size &lt;&lt; <span class="Constant">&quot; locations, that's too much compared to &quot;</span> &lt;&lt; Initial_memory_per_routine &lt;&lt; <span class="Constant">&quot;.</span><span class="cSpecial">\n</span><span class="Constant">&quot;</span><span class="Delimiter">;</span>
    exit<span class="Delimiter">(</span><span class="Constant">0</span><span class="Delimiter">);</span>
  <span class="Delimiter">}</span>
  <span class="Normal">if</span> <span class="Delimiter">(</span>Current_routine<span class="Delimiter">-&gt;</span>alloc + size &gt; Current_routine<span class="Delimiter">-&gt;</span>alloc_max<span class="Delimiter">)</span> <span class="Delimiter">{</span>
    <span class="Comment">// waste the remaining space and create a new chunk</span>
    Current_routine<span class="Delimiter">-&gt;</span>alloc = Memory_allocated_until<span class="Delimiter">;</span>
    Memory_allocated_until += Initial_memory_per_routine<span class="Delimiter">;</span>
    Current_routine<span class="Delimiter">-&gt;</span>alloc_max = Memory_allocated_until<span class="Delimiter">;</span>
    trace<span class="Delimiter">(</span><span class="Constant">9999</span><span class="Delimiter">,</span> <span class="Constant">&quot;new&quot;</span><span class="Delimiter">)</span> &lt;&lt; <span class="Constant">&quot;routine allocated memory from &quot;</span> &lt;&lt; Current_routine<span class="Delimiter">-&gt;</span>alloc &lt;&lt; <span class="Constant">&quot; to &quot;</span> &lt;&lt; Current_routine<span class="Delimiter">-&gt;</span>alloc_max &lt;&lt; end<span class="Delimiter">();</span>
  <span class="Delimiter">}</span>
<span class="Delimiter">}</span>

<span class="Delimiter">:(scenario new_initializes)</span>
<span class="Special">% Memory_allocated_until = 10;</span>
<span class="Special">% put(Memory, Memory_allocated_until, 1);</span>
<span class="muRecipe">def</span> main [
  <span class="Constant">1</span>:address:num<span class="Special"> &lt;- </span><span class="Normal">new</span> <span class="Constant">number:type</span>
]
<span class="traceContains">+mem: storing 0 in location 10</span>

<span class="Delimiter">:(scenario new_size)</span>
<span class="muRecipe">def</span> main [
  <span class="Constant">11</span>:address:num/<span class="Special">raw &lt;- </span><span class="Normal">new</span> <span class="Constant">number:type</span>
  <span class="Constant">12</span>:address:num/<span class="Special">raw &lt;- </span><span class="Normal">new</span> <span class="Constant">number:type</span>
  <span class="Constant">13</span>:num/<span class="Special">raw &lt;- </span>subtract <span class="Constant">12</span>:address:num/<span class="Special">raw</span><span class="Delimiter">,</span> <span class="Constant">11</span>:address:num/<span class="Special">raw</span>
]
<span class="Comment"># size of number + refcount</span>
<span class="traceContains">+mem: storing 2 in location 13</span>

<span class="Delimiter">:(scenario new_array_size)</span>
<span class="muRecipe">def</span> main [
  <span class="Constant">1</span>:address:array:num/<span class="Special">raw &lt;- </span><span class="Normal">new</span> <span class="Constant">number:type</span><span class="Delimiter">,</span> <span class="Constant">5</span>
  <span class="Constant">2</span>:address:num/<span class="Special">raw &lt;- </span><span class="Normal">new</span> <span class="Constant">number:type</span>
  <span class="Constant">3</span>:num/<span class="Special">raw &lt;- </span>subtract <span class="Constant">2</span>:address:num/<span class="Special">raw</span><span class="Delimiter">,</span> <span class="Constant">1</span>:address:array:num/<span class="Special">raw</span>
]
<span class="Comment"># 5 locations for array contents + array length + refcount</span>
<span class="traceContains">+mem: storing 7 in location 3</span>

<span class="Delimiter">:(scenario new_empty_array)</span>
<span class="muRecipe">def</span> main [
  <span class="Constant">1</span>:address:array:num/<span class="Special">raw &lt;- </span><span class="Normal">new</span> <span class="Constant">number:type</span><span class="Delimiter">,</span> <span class="Constant">0</span>
  <span class="Constant">2</span>:address:num/<span class="Special">raw &lt;- </span><span class="Normal">new</span> <span class="Constant">number:type</span>
  <span class="Constant">3</span>:num/<span class="Special">raw &lt;- </span>subtract <span class="Constant">2</span>:address:num/<span class="Special">raw</span><span class="Delimiter">,</span> <span class="Constant">1</span>:address:array:num/<span class="Special">raw</span>
]
<span class="traceContains">+run: {1: (&quot;address&quot; &quot;array&quot; &quot;number&quot;), &quot;raw&quot;: ()} &lt;- new {number: &quot;type&quot;}, {0: &quot;literal&quot;}</span>
<span class="traceContains">+mem: array length is 0</span>
<span class="Comment"># one location for array length, and one for the refcount</span>
<span class="traceContains">+mem: storing 2 in location 3</span>

<span class="Comment">//: If a routine runs out of its initial allocation, it should allocate more.</span>
<span class="Delimiter">:(scenario new_overflow)</span>
<span class="Special">% Initial_memory_per_routine = 3;  // barely enough room for point allocation below</span>
<span class="muRecipe">def</span> main [
  <span class="Constant">1</span>:address:num/<span class="Special">raw &lt;- </span><span class="Normal">new</span> <span class="Constant">number:type</span>
  <span class="Constant">2</span>:address:point/<span class="Special">raw &lt;- </span><span class="Normal">new</span> <span class="Constant">point:type</span>  <span class="Comment"># not enough room in initial page</span>
]
<span class="traceContains">+new: routine allocated memory from 1000 to 1003</span>
<span class="traceContains">+new: routine allocated memory from 1003 to 1006</span>
</pre>
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