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<title>3/fds</title>
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<!--Weave of '3/idn' generated by 7-->
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<ul class="crumbs"><li><a href="../webs.html">★</a></li><li><a href="index.html">words</a></li><li><a href="index.html#3">Chapter 3: Words in Sequence</a></li><li><b>Identifiers</b></li></ul><p class="purpose">To represent snippets of natural language in identifier form, which a typical C-like compiler would accept.</p>
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<ul class="toc"><li><a href="#SP1">§1. Validity of identifiers</a></li><li><a href="#SP3">§3. Automatically composed identifiers</a></li></ul><hr class="tocbar">
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<p class="inwebparagraph"><a id="SP1"></a><b>§1. Validity of identifiers. </b>In code compiled by I7, a valid identifier is a sequence of 1 to 31 characters,
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which must be alphanumeric or else underscores, except that the leading
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character must not be a 0:
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</p>
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<pre class="display">
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<span class="reserved">int</span><span class="plain"> </span><span class="functiontext">Identifiers::valid</span><span class="plain">(</span><span class="identifier">wchar_t</span><span class="plain"> *</span><span class="identifier">p</span><span class="plain">) {</span>
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<span class="reserved">if</span><span class="plain"> ((</span><span class="identifier">Wide::len</span><span class="plain">(</span><span class="identifier">p</span><span class="plain">) == 0) || (</span><span class="identifier">Wide::len</span><span class="plain">(</span><span class="identifier">p</span><span class="plain">) > 31)) </span><span class="reserved">return</span><span class="plain"> </span><span class="identifier">FALSE</span><span class="plain">;</span>
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<span class="reserved">for</span><span class="plain"> (</span><span class="reserved">int</span><span class="plain"> </span><span class="identifier">i</span><span class="plain">=0; </span><span class="identifier">p</span><span class="plain">[</span><span class="identifier">i</span><span class="plain">]; </span><span class="identifier">i</span><span class="plain">++)</span>
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<span class="reserved">if</span><span class="plain"> ((</span><span class="identifier">Characters::isdigit</span><span class="plain">(</span><span class="identifier">p</span><span class="plain">[</span><span class="identifier">i</span><span class="plain">]) == 0) && (</span><span class="identifier">Characters::isalpha</span><span class="plain">(</span><span class="identifier">p</span><span class="plain">[</span><span class="identifier">i</span><span class="plain">]) == 0) && (</span><span class="identifier">p</span><span class="plain">[</span><span class="identifier">i</span><span class="plain">] != </span><span class="character">'_'</span><span class="plain">))</span>
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<span class="reserved">return</span><span class="plain"> </span><span class="identifier">FALSE</span><span class="plain">;</span>
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<span class="reserved">if</span><span class="plain"> (</span><span class="identifier">Characters::isdigit</span><span class="plain">(</span><span class="identifier">p</span><span class="plain">[0])) </span><span class="reserved">return</span><span class="plain"> </span><span class="identifier">FALSE</span><span class="plain">;</span>
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<span class="reserved">return</span><span class="plain"> </span><span class="identifier">TRUE</span><span class="plain">;</span>
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<span class="plain">}</span>
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</pre>
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<p class="inwebparagraph"></p>
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<p class="endnote">The function Identifiers::valid appears nowhere else.</p>
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<p class="inwebparagraph"><a id="SP2"></a><b>§2. </b>The following flattens characters into shape:
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</p>
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<pre class="display">
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<span class="reserved">void</span><span class="plain"> </span><span class="functiontext">Identifiers::purify</span><span class="plain">(</span><span class="identifier">text_stream</span><span class="plain"> *</span><span class="identifier">identifier</span><span class="plain">) {</span>
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<span class="identifier">LOOP_THROUGH_TEXT</span><span class="plain">(</span><span class="identifier">pos</span><span class="plain">, </span><span class="identifier">identifier</span><span class="plain">) {</span>
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<span class="reserved">int</span><span class="plain"> </span><span class="identifier">x</span><span class="plain"> = </span><span class="identifier">Str::get</span><span class="plain">(</span><span class="identifier">pos</span><span class="plain">);</span>
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<span class="reserved">if</span><span class="plain"> (!(((</span><span class="identifier">x</span><span class="plain"> >= </span><span class="character">'0'</span><span class="plain">) && (</span><span class="identifier">x</span><span class="plain"> <= </span><span class="character">'9'</span><span class="plain">)) ||</span>
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<span class="plain">((</span><span class="identifier">x</span><span class="plain"> >= </span><span class="character">'a'</span><span class="plain">) && (</span><span class="identifier">x</span><span class="plain"> <= </span><span class="character">'z'</span><span class="plain">)) || ((</span><span class="identifier">x</span><span class="plain"> >= </span><span class="character">'A'</span><span class="plain">) && (</span><span class="identifier">x</span><span class="plain"> <= </span><span class="character">'Z'</span><span class="plain">)) || (</span><span class="identifier">x</span><span class="plain"> == </span><span class="character">'_'</span><span class="plain">)))</span>
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<span class="identifier">Str::put</span><span class="plain">(</span><span class="identifier">pos</span><span class="plain">, </span><span class="character">'_'</span><span class="plain">);</span>
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<span class="plain">}</span>
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<span class="plain">}</span>
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</pre>
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<p class="inwebparagraph"></p>
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<p class="endnote">The function Identifiers::purify is used in <a href="#SP3">§3</a>.</p>
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<p class="inwebparagraph"><a id="SP3"></a><b>§3. Automatically composed identifiers. </b>The following routines are no longer used by Inform, but retained in case
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useful for other projects.
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</p>
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<p class="inwebparagraph">The idea here is that we want an identifier based on a natural language
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wording, but which passed the above validity tests, and which does not lead
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tp namespace collisions. Such identifiers are composed in a pattern which
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uses an identifying letter (e.g., A for Action), a unique ID number
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(preventing name-clashes) and then a truncated alphanumeric-safe form of
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the words used in the textual description, if any. For example, an object
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called "apple crumble" might have identifier <code class="display"><span class="extract">O100_apple_crumble</span></code>. Any
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other object also called "apple crumble" would have a different identifier
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since the number parts would be different.
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</p>
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<p class="inwebparagraph">Beginning with the identifying letter ensures that we do not open with
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a 0 digit.
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</p>
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<p class="inwebparagraph">We truncate to 28 characters in length so that other routines can
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concatenate our identifier with up to 3 further characters, if they choose.
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</p>
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<pre class="display">
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<span class="reserved">void</span><span class="plain"> </span><span class="functiontext">Identifiers::compose</span><span class="plain">(</span><span class="identifier">text_stream</span><span class="plain"> *</span><span class="identifier">identifier</span><span class="plain">, </span><span class="reserved">int</span><span class="plain"> </span><span class="identifier">nature_character</span><span class="plain">, </span><span class="reserved">int</span><span class="plain"> </span><span class="identifier">id_number</span><span class="plain">, </span><span class="reserved">wording</span><span class="plain"> </span><span class="identifier">W</span><span class="plain">) {</span>
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<span class="identifier">Str::clear</span><span class="plain">(</span><span class="identifier">identifier</span><span class="plain">);</span>
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<span class="identifier">WRITE_TO</span><span class="plain">(</span><span class="identifier">identifier</span><span class="plain">, </span><span class="string">"%c%d"</span><span class="plain">, </span><span class="identifier">nature_character</span><span class="plain">, </span><span class="identifier">id_number</span><span class="plain">);</span>
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<span class="reserved">if</span><span class="plain"> (</span><span class="functiontext">Wordings::nonempty</span><span class="plain">(</span><span class="identifier">W</span><span class="plain">)) {</span>
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<span class="identifier">LOOP_THROUGH_WORDING</span><span class="plain">(</span><span class="identifier">j</span><span class="plain">, </span><span class="identifier">W</span><span class="plain">) {</span>
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<span class="comment">identifier is at this point 32 chars or fewer in length: add at most 30 more</span>
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<span class="reserved">if</span><span class="plain"> (</span><span class="identifier">Wide::len</span><span class="plain">(</span><span class="functiontext">Lexer::word_text</span><span class="plain">(</span><span class="identifier">j</span><span class="plain">)) > 30)</span>
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<span class="identifier">WRITE_TO</span><span class="plain">(</span><span class="identifier">identifier</span><span class="plain">, </span><span class="string">" etc"</span><span class="plain">);</span>
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<span class="reserved">else</span><span class="plain"> </span><span class="identifier">WRITE_TO</span><span class="plain">(</span><span class="identifier">identifier</span><span class="plain">, </span><span class="string">" %N"</span><span class="plain">, </span><span class="identifier">j</span><span class="plain">);</span>
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<span class="reserved">if</span><span class="plain"> (</span><span class="identifier">Str::len</span><span class="plain">(</span><span class="identifier">identifier</span><span class="plain">) > 32) </span><span class="reserved">break</span><span class="plain">;</span>
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<span class="plain">}</span>
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<span class="plain">}</span>
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<span class="identifier">Str::truncate</span><span class="plain">(</span><span class="identifier">identifier</span><span class="plain">, 28); </span> <span class="comment">it was at worst 62 chars in size, but is now truncated to 28</span>
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<span class="functiontext">Identifiers::purify</span><span class="plain">(</span><span class="identifier">identifier</span><span class="plain">);</span>
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<span class="plain">}</span>
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<span class="reserved">void</span><span class="plain"> </span><span class="functiontext">Identifiers::compose_numberless</span><span class="plain">(</span><span class="identifier">text_stream</span><span class="plain"> *</span><span class="identifier">identifier</span><span class="plain">, </span><span class="identifier">text_stream</span><span class="plain"> *</span><span class="identifier">prefix</span><span class="plain">, </span><span class="reserved">wording</span><span class="plain"> </span><span class="identifier">W</span><span class="plain">) {</span>
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<span class="identifier">Str::copy</span><span class="plain">(</span><span class="identifier">identifier</span><span class="plain">, </span><span class="identifier">prefix</span><span class="plain">);</span>
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<span class="reserved">if</span><span class="plain"> (</span><span class="functiontext">Wordings::nonempty</span><span class="plain">(</span><span class="identifier">W</span><span class="plain">)) {</span>
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<span class="identifier">LOOP_THROUGH_WORDING</span><span class="plain">(</span><span class="identifier">j</span><span class="plain">, </span><span class="identifier">W</span><span class="plain">) {</span>
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<span class="comment">identifier is at this point 32 chars or fewer in length: add at most 30 more</span>
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<span class="reserved">if</span><span class="plain"> (</span><span class="identifier">Wide::len</span><span class="plain">(</span><span class="functiontext">Lexer::word_text</span><span class="plain">(</span><span class="identifier">j</span><span class="plain">)) > 30)</span>
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<span class="identifier">WRITE_TO</span><span class="plain">(</span><span class="identifier">identifier</span><span class="plain">, </span><span class="string">" etc"</span><span class="plain">);</span>
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<span class="reserved">else</span><span class="plain"> </span><span class="identifier">WRITE_TO</span><span class="plain">(</span><span class="identifier">identifier</span><span class="plain">, </span><span class="string">" %N"</span><span class="plain">, </span><span class="identifier">j</span><span class="plain">);</span>
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<span class="reserved">if</span><span class="plain"> (</span><span class="identifier">Str::len</span><span class="plain">(</span><span class="identifier">identifier</span><span class="plain">) > 32) </span><span class="reserved">break</span><span class="plain">;</span>
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<span class="plain">}</span>
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<span class="plain">}</span>
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<span class="identifier">Str::truncate</span><span class="plain">(</span><span class="identifier">identifier</span><span class="plain">, 28); </span> <span class="comment">it was at worst 62 chars in size, but is now truncated to 28</span>
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<span class="functiontext">Identifiers::purify</span><span class="plain">(</span><span class="identifier">identifier</span><span class="plain">);</span>
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<span class="plain">}</span>
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</pre>
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<p class="inwebparagraph"></p>
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<p class="endnote">The function Identifiers::compose appears nowhere else.</p>
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<p class="endnote">The function Identifiers::compose_numberless appears nowhere else.</p>
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<hr class="tocbar">
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<ul class="toc"><li><a href="3-fds.html">Back to 'Feeds'</a></li><li><i>(This section ends Chapter 3: Words in Sequence.)</i></li></ul><hr class="tocbar">
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<!--End of weave-->
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