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<!--Weave of 'Startup Template' generated by Inweb-->
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<div class="breadcrumbs">
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<ul class="crumbs"><li><a href="../index.html">Home</a></li><li><a href="../extensions.html">Kits</a></li><li><a href="index.html">BasicInformKit</a></li><li><b>Startup Template</b></li></ul></div>
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<p class="purpose">How the program starts up, in a Basic Inform project.</p>
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<ul class="toc"><li><a href="S-str.html#SP1">§1. Summary</a></li><li><a href="S-str.html#SP2">§2. The startup sequence</a></li><li><a href="S-str.html#SP3">§3. Initialise Memory Rule</a></li><li><a href="S-str.html#SP4">§4. Seed Random Number Generator Rule</a></li></ul><hr class="tocbar">
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<p class="commentary firstcommentary"><a id="SP1" class="paragraph-anchor"></a><b>§1. Summary. </b>These rules perform the essential tasks required for setting up the virtual
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machine. This includes checking that we are running in a compatible interpreter,
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and setting up various built in Glk objects (when running in a Glk interpreter).
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</p>
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<p class="commentary">These rules here are the ones which get the basic machinery working
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to the point where it is safe to run arbitrary I7 source text. They necessarily
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do very low-level things, and it is not guaranteed that I7 phrases will behave
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to specification if executed before these early rules have finished. So it
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is hazardous to obstruct or alter them.
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</p>
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<p class="commentary">Arrangements are a little different here on the Z-machine, because some
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data is retained in the case of a restart.
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</p>
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<p class="commentary">(Many thanks are due to Eliuk Blau, who found several tricky timing errors
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here and elsewhere in the Glulx-specific code. Frankly, I feel like hanging
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a sign on the following routines which reads "Congratulations on bringing
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light to the Dark Room.")
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</p>
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<p class="commentary firstcommentary"><a id="SP2" class="paragraph-anchor"></a><b>§2. The startup sequence. </b>As of IE-0022 we have a simplified startup sequence. <span class="extract"><span class="extract-syntax">Main</span></span> calls the <span class="extract"><span class="extract-syntax">Startup</span></span>
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function, which does two things: run an Architecture16Kit/Architecture32Kit function
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<span class="extract"><span class="extract-syntax">VM_Check_Functionality</span></span> which checks the VM meets the minimum requirements for Inform
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(in Glulx it would test a few Glulx/Glk gestalts; in Z-Code it would probably do
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nothing.) Then it runs the Startup Rules. And that's it - everything else in the
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startup sequence is now in Inform-accessible rules.
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</p>
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<p class="commentary">Because the functions below are replaced by <span class="extract"><span class="extract-syntax">WorldModelKit</span></span> alternatives
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if that kit is present, the following applies only to Basic Inform programs
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where <span class="extract"><span class="extract-syntax">WorldModelKit</span></span> is not involved.
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</p>
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<pre class="displayed-code all-displayed-code code-font">
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<span class="plain-syntax">[ </span><span class="identifier-syntax">Main</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">self</span><span class="plain-syntax"> = </span><span class="identifier-syntax">COL_HSIZE</span><span class="plain-syntax">; </span><span class="comment-syntax">To ensure this definition is not optimised out</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">Startup</span><span class="plain-syntax">();</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">Submain</span><span class="plain-syntax">();</span>
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<span class="plain-syntax">];</span>
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<span class="plain-syntax">[ </span><span class="identifier-syntax">Startup</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">VM_Check_Functionality</span><span class="plain-syntax">();</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">say__pc</span><span class="plain-syntax"> = </span><span class="identifier-syntax">say__pc</span><span class="plain-syntax"> | </span><span class="identifier-syntax">PARA_NORULEBOOKBREAKS</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">FollowRulebook</span><span class="plain-syntax">(</span><span class="identifier-syntax">STARTUP_RB</span><span class="plain-syntax">);</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">say__pc</span><span class="plain-syntax"> & </span><span class="identifier-syntax">PARA_NORULEBOOKBREAKS</span><span class="plain-syntax">) </span><span class="identifier-syntax">say__pc</span><span class="plain-syntax"> = </span><span class="identifier-syntax">say__pc</span><span class="plain-syntax"> - </span><span class="identifier-syntax">PARA_NORULEBOOKBREAKS</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">rfalse</span><span class="plain-syntax">;</span>
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<span class="plain-syntax">];</span>
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</pre>
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<p class="commentary firstcommentary"><a id="SP3" class="paragraph-anchor"></a><b>§3. Initialise Memory Rule. </b>This rule amalgamates some minimal initialisations which all need to happen
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before we can risk using some of the more exotic I7 kinds:
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</p>
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<ul class="items"><li>(a) The language definition might call for initialisation, although the
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default language of play (English) does not.
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</li><li>(b) We start the machinery needed to check that property accesses are
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valid during play.
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</li><li>(c) We initialise the memory allocation heap, and expand the literal
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constants, as hinted above: these are called "block constants" since
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they occupy blocks of memory.
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</li><li>(d) Some architecture-specific dictionary and parse buffer related globals
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are initialised.
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</li></ul>
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<pre class="displayed-code all-displayed-code code-font">
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<span class="plain-syntax">[ </span><span class="identifier-syntax">INITIALISE_MEMORY_R</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">LanguageInitialise</span><span class="plain-syntax">();</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">HeapInitialise</span><span class="plain-syntax">(); </span><span class="comment-syntax">Create a completely unused memory allocation heap</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">StackFramingInitialise</span><span class="plain-syntax">(); </span><span class="comment-syntax">Create an empty stack</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">CreateDynamicRelations</span><span class="plain-syntax">(); </span><span class="comment-syntax">Create relation structures on the heap</span>
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<span class="plain-syntax"> #</span><span class="identifier-syntax">Ifdef</span><span class="plain-syntax"> </span><span class="identifier-syntax">TARGET_GLULX</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="comment-syntax">Empty the parse buffer (see bug 0001451)</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">buffer3</span><span class="plain-syntax">-->0 = </span><span class="constant-syntax">0</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> #</span><span class="identifier-syntax">Ifnot</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">standard_interpreter</span><span class="plain-syntax"> = </span><span class="identifier-syntax">HDR_TERPSTANDARD</span><span class="plain-syntax">-->0;</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">dict_start</span><span class="plain-syntax"> = </span><span class="identifier-syntax">HDR_DICTIONARY</span><span class="plain-syntax">-->0;</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">dict_entry_size</span><span class="plain-syntax"> = </span><span class="identifier-syntax">dict_start</span><span class="plain-syntax">->(</span><span class="identifier-syntax">dict_start</span><span class="plain-syntax">->0 + </span><span class="constant-syntax">1</span><span class="plain-syntax">);</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">dict_start</span><span class="plain-syntax"> = </span><span class="identifier-syntax">dict_start</span><span class="plain-syntax"> + </span><span class="identifier-syntax">dict_start</span><span class="plain-syntax">->0 + </span><span class="constant-syntax">4</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">dict_end</span><span class="plain-syntax"> = </span><span class="identifier-syntax">dict_start</span><span class="plain-syntax"> + ((</span><span class="identifier-syntax">dict_start</span><span class="plain-syntax"> - </span><span class="constant-syntax">2</span><span class="plain-syntax">)-->0) * </span><span class="identifier-syntax">dict_entry_size</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">buffer</span><span class="plain-syntax">->0 = </span><span class="identifier-syntax">INPUT_BUFFER_LEN</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">buffer2</span><span class="plain-syntax">->0 = </span><span class="identifier-syntax">INPUT_BUFFER_LEN</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">buffer3</span><span class="plain-syntax">->0 = </span><span class="identifier-syntax">INPUT_BUFFER_LEN</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">parse</span><span class="plain-syntax">->0 = </span><span class="constant-syntax">15</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">parse2</span><span class="plain-syntax">->0 = </span><span class="constant-syntax">15</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> #</span><span class="identifier-syntax">Endif</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">rfalse</span><span class="plain-syntax">;</span>
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<span class="plain-syntax">];</span>
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</pre>
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<p class="commentary firstcommentary"><a id="SP4" class="paragraph-anchor"></a><b>§4. Seed Random Number Generator Rule. </b>Unless a seed is provided by Inform, and it won't be for released story files,
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the VM's interpreter is supposed to start up with a good seed in its random
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number generator: something usually derived from, say, the milliseconds part
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of the current time of day, which is unlikely to repeat or show any pattern
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in real-world use. However, early Z-machine interpreters often did this quite
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badly, starting with poor seed values which meant that the first few random
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numbers always had something in common (being fairly small in their range,
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for instance). To obviate this we extract and throw away 100 random numbers
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to get the generator going, shaking out more obvious early patterns, but
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that cannot really help much if the VM interpreter's RNG is badly written.
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"Anyone who considers arithmetical methods of producing random digits is,
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of course, in a state of sin" (von Neumann).
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</p>
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<pre class="displayed-code all-displayed-code code-font">
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<span class="plain-syntax">[ </span><span class="identifier-syntax">SEED_RANDOM_NUMBER_GENERATOR_R</span><span class="plain-syntax"> </span><span class="identifier-syntax">i</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">BasicInformKit</span><span class="plain-syntax">`</span><span class="identifier-syntax">FIX_RNG_CFGF</span><span class="plain-syntax">) {</span>
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<span class="plain-syntax"> #</span><span class="identifier-syntax">Ifdef</span><span class="plain-syntax"> </span><span class="identifier-syntax">TARGET_GLULX</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> @</span><span class="reserved-syntax">random</span><span class="plain-syntax"> </span><span class="constant-syntax">10000</span><span class="plain-syntax"> </span><span class="identifier-syntax">i</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">i</span><span class="plain-syntax"> = -</span><span class="identifier-syntax">i</span><span class="plain-syntax">-2000;</span>
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<span class="plain-syntax"> @</span><span class="identifier-syntax">setrandom</span><span class="plain-syntax"> </span><span class="identifier-syntax">i</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> #</span><span class="identifier-syntax">Ifnot</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> @</span><span class="reserved-syntax">random</span><span class="plain-syntax"> </span><span class="constant-syntax">10000</span><span class="plain-syntax"> -> </span><span class="identifier-syntax">i</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">i</span><span class="plain-syntax"> = -</span><span class="identifier-syntax">i</span><span class="plain-syntax">-2000;</span>
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<span class="plain-syntax"> @</span><span class="reserved-syntax">random</span><span class="plain-syntax"> </span><span class="identifier-syntax">i</span><span class="plain-syntax"> -> </span><span class="identifier-syntax">i</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> #</span><span class="identifier-syntax">Endif</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> }</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">RNG_SEED_AT_START_OF_PLAY</span><span class="plain-syntax">) </span><span class="identifier-syntax">VM_Seed_RNG</span><span class="plain-syntax">(</span><span class="identifier-syntax">RNG_SEED_AT_START_OF_PLAY</span><span class="plain-syntax">);</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">for</span><span class="plain-syntax"> (</span><span class="identifier-syntax">i</span><span class="plain-syntax">=1: </span><span class="identifier-syntax">i</span><span class="plain-syntax"><=100: </span><span class="identifier-syntax">i</span><span class="plain-syntax">++) </span><span class="reserved-syntax">random</span><span class="plain-syntax">(</span><span class="identifier-syntax">i</span><span class="plain-syntax">);</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">rfalse</span><span class="plain-syntax">;</span>
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<span class="plain-syntax">];</span>
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