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PORegex: negative look-ahead between two matches
 

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  1. PORegex: negative look-ahead between two matches
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    <p>I'm trying to build a regex somewhat like this:</p> <pre><code>[match-word] ... [exclude-specific-word] ... [match-word] </code></pre> <p>This seems to work with a negative look-ahead, but I'm running into a problem when I have a case like this:</p> <pre><code>[match-word] ... [exclude-specific-word] ... [match-word] ... [excluded word appears again] </code></pre> <p>I want the above sentence to match, but the negative look-ahead between the first and the second matched word "spills over" so the second word is never matched. </p> <p>Let's look at a practical example. </p> <p>I wan't to match every sentence which has the word "i" and the word "pie", but not the word "hate" in between those two words. I have these three sentences:</p> <pre><code>i sure like eating pie, but i love donuts &lt;- Want to match this i sure like eating pie, but i hate donuts &lt;- Want to match this i sure hate eating pie, but i like donuts &lt;- Don't want to match this </code></pre> <p>I have this regex:</p> <pre><code>^i(?!.*hate).*pie - have removed the word boundaries for clarity, original is: ^i\b(?!.*\bhate\b).*\bpie\b </code></pre> <p>Which matches the first sentence, but not the second one, because the negative look-ahead scans the whole string.</p> <p>Is there a way to limit the negative look-ahead, so that it's satisfied if it encounters "pie" before it encounters "hate"?</p> <p>Note: in my implementation, there may be other terms following this regex (it's built dynamically from a grammar search engine), for instance:</p> <pre><code>^i(?!.*hate).*pie.*donuts </code></pre> <p>I'm currently using JRegex, but could probably switch to JDK Regex if necessary</p> <p><strong>Update</strong>: I forgot to mention something in my initial question:</p> <p>It's possible that the "negative construct" exists further in the sentence, and I do want to match the sentence if it's possible even if the "negative" construct exists further up.</p> <p>To clarify, look at these sentences:</p> <pre><code>i sure like eating pie, but i love donuts &lt;- Want to match this i sure like eating pie, but i hate donuts &lt;- Want to match this i sure hate eating pie, but i like donuts &lt;- Don't want to match this i sure like eating pie, but i like donuts and i hate making pie &lt;- Do want to match this </code></pre> <p>rob's answer works perfectly for this extra constraint, so I'm accepting that one.</p>
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    1. USAlexander Malfait
    1. USAlexander Malfait
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