SCIP in C++11 ― 2.2.3節 その3

木の演算：問題2.35

以前、listやtupleでは挫折した問題。

今度は簡単。

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//count-leaves (accumulate ver.)

const function<int(int,int)> add=

    [](const int x, const int y){return(x+y);};

const int countLeavesAcc(const List& listTree)

{

    function<int(List)> countRecursively;

    countRecursively=[listTree]

        (const List& x)

        {

            if(isNull(x)){return(0);}

            if(!isPair(x)){return(1);}

            return(countLeavesAcc(x));

        };

    return(accumulate

           (add,0,mapping

            (countRecursively,listTree)));

}

//---------abstraction barrier---------

int main(int argc, char** argv)

{

    const auto listTree(makeList(1,makeList(2,makeList(3,4),5)));

    cout<<"t = "<<listString(listTree)<<endl;

    cout<<"(count-leaves t) = "<<countLeavesAcc(listTree)<<endl;

   

    return(0);

}

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出力

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t = (1 (2 (3 4) 5))

(count-leaves t) = 5