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POHow to remove an extra {} in this use of DeleteCases
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copied!<p>(<em>Mathematica</em> version: 8.0.4)</p> <p>Given</p> <pre><code>lst = {{{{1, 2}, 3}, {{4, 5}, 6}}, {{{7, 8, 9, 10, 11}, 13}}}; lst2 = DeleteCases[lst, {x_, y_} /; y > 6, {2}] </code></pre> <p>gives</p> <pre><code>{{{{1, 2}, 3}, {{4, 5}, 6}}, {}} </code></pre> <p>Note the extra empty <code>{}</code> at the end.</p> <p>I could not find a way to remove it in the same command using <code>DeleteCases</code> (which I think the right command to use for this), so I had to apply it again on the result</p> <pre><code>lst2 = DeleteCases[lst2, {}] {{{{1, 2}, 3}, {{4, 5}, 6}}} </code></pre> <p><strong>question: Is there a trick to do the above in one command without getting the empty <code>{}</code> in the result? so that the command is self contained for all cases?</strong></p> <p><strong>updatet 1</strong></p> <p>response to Lou suggestion below, of adding an extra <code>{ }</code></p> <p>Here is an example where I get different results:</p> <pre><code>lst={{{{1, 2}, 3}, {{4, 5}, 6}}, {{{7, 8, 9, 10, 11}, 13}}} </code></pre> <p>now using the method of removing empty <code>{}</code> by an extra application of <code>DeleteCases</code>, we get</p> <pre><code>lst2 = DeleteCases[lst, {x_, y_} /; y >= 6, {2}] {{{{1, 2}, 3}}, {}} lst2 = DeleteCases[lst2, {}] {{{{1, 2}, 3}}} </code></pre> <p>now using the method of extra <code>{ }</code></p> <pre><code>lst2 = DeleteCases[lst, {{x_, y_}} /; y >= 6] {{{{1, 2}, 3}, {{4, 5}, 6}}} </code></pre> <p>which is the not the same, I should get only <code>{{{{1, 2}, 3}}}</code></p> <p>thanks</p>

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