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<!--Weave of 'Parsing Literals' generated by Inweb-->
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<ul class="crumbs"><li><a href="../index.html">Home</a></li><li><a href="../inform7n.html">Inform7</a></li><li><a href="index.html">values</a></li><li><a href="index.html#3">Chapter 3: Literals</a></li><li><b>Parsing Literals</b></li></ul></div>
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<p class="purpose">To decide if an excerpt of text is a value referred to notationally rather than by name.</p>
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<p class="commentary firstcommentary"><a id="SP1" class="paragraph-anchor"></a><b>§1. </b>The nonterminal <s-literal> matches any literal, and on success produces
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an rvalue specification for the given value. Note that not every constant
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is a literal: names of objects, or of rules, for example, are not literals
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but they are certainly constants.
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</p>
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<p class="commentary">Note also that ordinal numbers are not valid as literals: "2nd" is not a noun.
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</p>
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<pre class="Preform-displayed-code all-displayed-code code-font">
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<span class="Preform-function-syntax"><s-literal></span><span class="Preform-plain-syntax"> </span><span class="Preform-reserved-syntax">::=</span>
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<span class="Preform-plain-syntax"> </span><span class="Preform-function-syntax"><cardinal-number></span><span class="Preform-plain-syntax"> </span><span class="Preform-reserved-syntax">|</span><span class="Preform-plain-syntax"> </span><span class="Preform-reserved-syntax">==></span><span class="Preform-plain-syntax"> { -, Rvalues::from_int(R[1], W) }</span>
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<span class="Preform-plain-syntax"> </span><span class="Preform-constant-syntax">minus</span><span class="Preform-plain-syntax"> </span><span class="Preform-function-syntax"><cardinal-number></span><span class="Preform-plain-syntax"> </span><span class="Preform-reserved-syntax">|</span><span class="Preform-plain-syntax"> </span><span class="Preform-reserved-syntax">==></span><span class="Preform-plain-syntax"> { -, Rvalues::from_int(-R[1], W) }</span>
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<span class="Preform-plain-syntax"> </span><span class="Preform-function-syntax"><quoted-text></span><span class="Preform-plain-syntax"> </span><span class="Preform-reserved-syntax">(</span><span class="Preform-plain-syntax"> </span><span class="Preform-function-syntax"><response-letter></span><span class="Preform-plain-syntax"> </span><span class="Preform-reserved-syntax">)</span><span class="Preform-plain-syntax"> </span><span class="Preform-reserved-syntax">|</span><span class="Preform-plain-syntax"> </span><span class="Preform-reserved-syntax">==></span><span class="Preform-plain-syntax"> { -, Rvalues::from_wording(W) }</span>
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<span class="Preform-plain-syntax"> </span><span class="Preform-function-syntax"><quoted-text></span><span class="Preform-plain-syntax"> </span><span class="Preform-reserved-syntax">|</span><span class="Preform-plain-syntax"> </span><span class="Preform-reserved-syntax">==></span><span class="Preform-plain-syntax"> { -, Rvalues::from_wording(W) }</span>
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<span class="Preform-plain-syntax"> </span><span class="Preform-function-syntax"><s-literal-real-number></span><span class="Preform-plain-syntax"> </span><span class="Preform-reserved-syntax">|</span><span class="Preform-plain-syntax"> </span><span class="Preform-reserved-syntax">==></span><span class="Preform-plain-syntax"> { pass 1 }</span>
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<span class="Preform-plain-syntax"> </span><span class="Preform-function-syntax"><s-literal-truth-state></span><span class="Preform-plain-syntax"> </span><span class="Preform-reserved-syntax">|</span><span class="Preform-plain-syntax"> </span><span class="Preform-reserved-syntax">==></span><span class="Preform-plain-syntax"> { pass 1 }</span>
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<span class="Preform-plain-syntax"> </span><span class="Preform-function-syntax"><s-literal-list></span><span class="Preform-plain-syntax"> </span><span class="Preform-reserved-syntax">|</span><span class="Preform-plain-syntax"> </span><span class="Preform-reserved-syntax">==></span><span class="Preform-plain-syntax"> { pass 1 }</span>
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<span class="Preform-plain-syntax"> </span><span class="Preform-constant-syntax">unicode</span><span class="Preform-plain-syntax"> </span><span class="Preform-function-syntax"><s-unicode-character></span><span class="Preform-plain-syntax"> </span><span class="Preform-reserved-syntax">|</span><span class="Preform-plain-syntax"> </span><span class="Preform-reserved-syntax">==></span><span class="Preform-plain-syntax"> { pass 1 }</span>
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<span class="Preform-plain-syntax"> </span><span class="Preform-function-syntax"><s-literal-time></span><span class="Preform-plain-syntax"> </span><span class="Preform-reserved-syntax">|</span><span class="Preform-plain-syntax"> </span><span class="Preform-reserved-syntax">==></span><span class="Preform-plain-syntax"> { pass 1 }</span>
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<span class="Preform-plain-syntax"> </span><span class="Preform-function-syntax"><s-literal-unit-notation></span><span class="Preform-plain-syntax"> </span><span class="Preform-reserved-syntax">==></span><span class="Preform-plain-syntax"> { pass 1 }</span>
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</pre>
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<ul class="endnotetexts"><li>This is <a href="../words-module/4-ap.html" class="internal">Preform grammar</a>, not regular C code.</li></ul>
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<p class="commentary firstcommentary"><a id="SP2" class="paragraph-anchor"></a><b>§2. </b>Response letters A to Z mark certain texts as being responses. These are only
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meaningful (and allowed) in the body of rules, but are syntactically valid as
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literals anywhere.
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</p>
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<pre class="Preform-displayed-code all-displayed-code code-font">
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<span class="Preform-function-syntax"><response-letter></span><span class="Preform-plain-syntax"> </span><span class="Preform-constant-syntax">internal</span><span class="Preform-plain-syntax"> </span><span class="Preform-constant-syntax">1</span><span class="Preform-plain-syntax"> </span><span class="Preform-constant-syntax">{</span>
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<span class="Preform-plain-syntax"> </span><span class="Preform-identifier-syntax">wchar_t</span><span class="Preform-plain-syntax"> *</span><span class="Preform-identifier-syntax">p</span><span class="Preform-plain-syntax"> = </span><span class="Preform-identifier-syntax">Lexer::word_raw_text</span><span class="Preform-plain-syntax">(</span><span class="Preform-identifier-syntax">Wordings::first_wn</span><span class="Preform-plain-syntax">(</span><span class="Preform-identifier-syntax">W</span><span class="Preform-plain-syntax">));</span>
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<span class="Preform-plain-syntax"> </span><span class="Preform-reserved-syntax">if</span><span class="Preform-plain-syntax"> ((</span><span class="Preform-identifier-syntax">p</span><span class="Preform-plain-syntax">) && (</span><span class="Preform-identifier-syntax">p</span><span class="Preform-plain-syntax">[0] >= </span><span class="Preform-character-syntax">'A'</span><span class="Preform-plain-syntax">) && (</span><span class="Preform-identifier-syntax">p</span><span class="Preform-plain-syntax">[0] <= </span><span class="Preform-character-syntax">'Z'</span><span class="Preform-plain-syntax">) && (</span><span class="Preform-identifier-syntax">p</span><span class="Preform-plain-syntax">[1] == </span><span class="Preform-constant-syntax">0</span><span class="Preform-plain-syntax">)) {</span>
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<span class="Preform-plain-syntax"> ==> { </span><span class="Preform-identifier-syntax">p</span><span class="Preform-plain-syntax">[0]-</span><span class="Preform-character-syntax">'A'</span><span class="Preform-plain-syntax">, - };</span>
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<span class="Preform-plain-syntax"> </span><span class="Preform-reserved-syntax">return</span><span class="Preform-plain-syntax"> </span><span class="Preform-identifier-syntax">TRUE</span><span class="Preform-plain-syntax">;</span>
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<span class="Preform-plain-syntax"> }</span>
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<span class="Preform-plain-syntax"> ==> { </span><span class="Preform-identifier-syntax">fail</span><span class="Preform-plain-syntax"> </span><span class="Preform-identifier-syntax">nonterminal</span><span class="Preform-plain-syntax"> };</span>
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<span class="Preform-plain-syntax">}</span>
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</pre>
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<ul class="endnotetexts"><li>This is <a href="../words-module/4-ap.html" class="internal">Preform grammar</a>, not regular C code.</li></ul>
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<p class="commentary firstcommentary"><a id="SP3" class="paragraph-anchor"></a><b>§3. </b>It might seem odd that the truth states count as literals, whereas names of
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instances of other kinds (people, say) do not. The argument for this is that
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there are always necessarily exactly two truth states, whereas there could
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in principle be any number of people, colours, vehicles, and such.
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</p>
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<pre class="Preform-displayed-code all-displayed-code code-font">
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<span class="Preform-function-syntax"><s-literal-truth-state></span><span class="Preform-plain-syntax"> </span><span class="Preform-reserved-syntax">::=</span>
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<span class="Preform-plain-syntax"> </span><span class="Preform-constant-syntax">false</span><span class="Preform-plain-syntax"> </span><span class="Preform-reserved-syntax">|</span><span class="Preform-plain-syntax"> </span><span class="Preform-reserved-syntax">==></span><span class="Preform-plain-syntax"> { -, Rvalues::from_boolean(FALSE, W) }</span>
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<span class="Preform-plain-syntax"> </span><span class="Preform-constant-syntax">true</span><span class="Preform-plain-syntax"> </span><span class="Preform-reserved-syntax">==></span><span class="Preform-plain-syntax"> { -, Rvalues::from_boolean(TRUE, W) }</span>
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</pre>
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<ul class="endnotetexts"><li>This is <a href="../words-module/4-ap.html" class="internal">Preform grammar</a>, not regular C code.</li></ul>
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