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POBetter solution than lex/yacc for parsing a DSL in C?
 

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  1. POBetter solution than lex/yacc for parsing a DSL in C?
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    <p>One of my programs accepts a commands (like <code>kill foo</code>) at runtime. Think of it as a little domain-specific language. Here are a few examples:</p> <pre><code>kill kill client exit </code></pre> <p>But also, chained commands are allowed and whitespace is not significant before and after commands, so the following examples are also valid:</p> <pre><code>kill ; say "that was fun" kill ; kill ; kill; </code></pre> <p>I have currently implemented this with lex/yacc (flex/bison to be specific) and that caused a lot of headache. The lexer very much depends on the context (for example whitespace tokens are generally not returned, unless after a <code>kill</code> keyword for example) and has many different states. The grammar used to have conflicts and I don’t really like the format in which it has to be specified (especially the $1, $2, $3, … to use arguments for non-terminals). Also, the error messages which bison provides (at parse-time) are sometimes accurate, but often not (the <code>kill</code> command with optional arguments leads to error messages like <code>Unexpected $undefined, expected $end or ;</code> for <code>kill clont</code> instead of <code>kill client</code>). Lastly, the C API for yacc is cruel (external defines all over the place).</p> <p>I am not asking you to solve all the aforementioned questions (I will open separate threads with more specific descriptions and code if there is no way around lex/yacc). Instead, I am interested in alternatives to lex/yacc.</p> <p>My criteria are the following:</p> <ul> <li>Input is a string (const char *), there is no output but instead some code should be called for each different keyword.</li> <li>I want to use this with C (C99).</li> <li>The software should be already included in the major linux distros or at least easy to bundle / package.</li> <li>It should be well-documented.</li> <li>The syntax for describing my language should be easy.</li> <li>It should output meaningful error messages upon parsing errors.</li> <li>Performance is not that important (of course it should be fast, but the typical use case is interactive usage, not processing tons of MB of commands).</li> </ul>
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    1. COKill, kill, kill!
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    2. CO@Philip: Yeah, you kind of get the feeling I had after messing with all the lexer/parser stuff… :)
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