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copied!<p>You need a value to pass to <code>equal_range</code>, and the obvious thing to use is a pointer. The obvious way to get one is just to create an instance of <code>B</code> with the correct value of <code>attr_</code>, and write a comparator that involves only the value of <code>attr()</code>. I'm going to assume you already know how to do that since you managed to get the vector sorted ;-)</p> <p>Provided there are no null pointers in the vector you could do this instead:</p> <pre><code>struct FindAttr { unsigned int attr; FindAttr(unsigned int attr) : attr(attr) {} bool operator()(B *left, B *right) { unsigned int leftval = left ? left->attr() : attr; unsigned int rightval = right ? right->attr() : attr; return leftval < rightval; } }; ... return equal_range(vec_.begin(), vec_.end(), nullptr, FindAttr(value)); </code></pre> <p>You could make that a lambda:</p> <pre><code>return equal_range(vec_.begin(), vec_.end(), nullptr, [=value](B *left, B *right) { unsigned int leftval = left ? left->attr() : attr; unsigned int rightval = right ? right->attr() : attr; return leftval < rightval; }); </code></pre> <p>You can actually cut out the pointer altogether, to give what I think is the "cleanest" solution:</p> <pre><code>struct FindAttr { bool operator()(B *left, unsigned int rightval) { return left->attr() < rightval; } bool operator()(unsigned int leftval, B *right) { return leftval < right->attr(); } }; ... return equal_range(vec_.begin(), vec_.end(), value, FindAttr()); </code></pre> <p>AFAIK there's no direct equivalent to this with a lambda, since lambdas can only have one call signature. I suppose you could write a lambda that takes a <code>boost::variant</code> (or any type that implicitly converts from both <code>unsigned int</code> and from <code>B*</code>, and that remembers which one it was).</p>

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