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POstd::map lower_bound is not returning the correct value
 

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  1. POstd::map lower_bound is not returning the correct value
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    <p>Good afternoon, I am trying to use the std::map lower_found member function. However , it keeps returning the wrong answer. Here is an excerpt of my test code. Please explain to me how to make std::map lower bound function properly. Thank you.</p> <pre><code>class Interval { public: explicit Interval(int item){ mLow = item; mHigh = item; mStamp = 0; } Interval(int low, int high, int stamp = 0){ mLow = low; mHigh = high; mStamp = stamp; } Interval(void){ mLow = 0; mHigh = 0; mStamp = 0; } Interval(const Interval&amp; r): mLow(r.mLow), mHigh(r.mHigh), mStamp(r.mStamp) { } bool operator&lt;(const Interval&amp; rhs) const{ if (mLow &lt; rhs.mLow){ return true; } return false; } // operator&lt; int low() const { return mLow; } int high() const { return mHigh; } int getStamp() const { return mStamp; } void setLow(int lower) { mLow = lower; } void setHigh(int higher) { mHigh = higher; } void setStamp(int stamp) { mStamp = stamp; } private: int mLow; int mHigh; int mStamp; }; // class Interval int main(int Argc_,char *Argv_[]) { int n; Interval r; std::map&lt;Interval, Interval&gt; Intervals_type; r.setLow(0); r.setHigh(10); r.setStamp(1); std::pair&lt; Interval, Interval &gt; tmp(r,r); Intervals_type.insert(tmp); r.setLow(10); r.setHigh(20); r.setStamp(2); std::pair&lt; Interval, Interval &gt; tmp2(r,r); Intervals_type.insert(tmp2); r.setLow(20); r.setHigh(30); r.setStamp(3); std::pair&lt; Interval, Interval &gt; tmp3(r,r); Intervals_type.insert(tmp3); r.setLow(30); r.setHigh(40); r.setStamp(4); std::pair&lt; Interval, Interval &gt; tmp4(r,r); Intervals_type.insert(tmp4); n = 36; std::map&lt;Interval, Interval&gt;::const_iterator it = Intervals_type.lower_bound(Interval(n)); if (it == Intervals_type.end()){ printf(" n = %d not found\n",n); } return 1; } </code></pre>
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    1. USFrank
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      1. VTUpMod
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    1. COWhat makes you think it returns the wrong result? What do you expect? What does it return?
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      1. USybungalobill
    2. COYou forgot to tell us what result you expected, and what you actually got. I would expect it to print "not found" as 36 is larger than all the keys in the map, so lower_bound would return the end() iterator.
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      1. USBo Persson
    3. COWhat does your program print, and what did you expect it to print?
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      1. USRobᵩ
 

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