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POHow can I write Bison rule with 0 or 1+ tokens without S/R conflicts?
 

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  1. POHow can I write Bison rule with 0 or 1+ tokens without S/R conflicts?
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    <p>If I defined tokens like normal <em>object access</em> :</p> <pre class="lang-cpp prettyprint-override"><code>[$_a-zA-Z]+[.] { return ACCESS; } [$_a-zA-Z]+ { return ID; } [+] { return PLUIS; } </code></pre> <p>And the Bison grammar rules:</p> <pre class="lang-cpp prettyprint-override"><code>Accesses : Accesses ACCESS { /*do something...*/ } | ACCESS { /*do something...*/ } Expression : Accesses ID PLUS Accesses ID { /*do something...*/ } </code></pre> <p>I want to allow such contents in source codes:</p> <pre class="lang-cpp prettyprint-override"><code>moduleA.valueB.valueC + valueD </code></pre> <p>In the example, if I don't put empty rule in <code>Accesses</code>, the single <code>ID</code> variable like <code>valueD</code> is illegal. But if I put the empty rule in, <code>Accesses</code> will cause seriously S/R conflicts, and texts it matched will become strange. </p> <p>And, I don't think duplicate the rules in <code>Expression</code> is a good idea, ex:</p> <pre class="lang-cpp prettyprint-override"><code>Expression : Accesses ID PLUS Accesses ID { /*do something...*/ } | ID PLUS Accesses ID { /*do something...*/ } | Accesses ID PLUS ID { /*do something...*/ } | ID PLUS ID { /*do something...*/ } </code></pre> <p>Can I find other ways to solve this problem ?</p> <p><strong>EDIT</strong>: Ok thanks to your answer noticed me this simple grammar got no conflicts. At least you let me know that the real problem may hide in somewhere else ( what a mess for a compiler newbie ! ). </p>
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    1. USsnowmantw
    1. USsnowmantw
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    1. COThere are no shift reduce conflicts from the Expression rule you have if you change the Accesses rule to allow epsilon, so the problem you have must be elsewhere...
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      1. POHow can I write Bison rule with 0 or 1+ tokens without S/R conflicts?
      1. USChris Dodd
 

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