SCIP in C++11 ― 3.1.1節その3

銀行口座その2：口座のパスワード保護と問題3.3～3.4

make-monitoredを問題3.2でしっかり作っておけば簡単。

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const function<function<List(List)>(string,List)> makeAccount

(const List& balanceIn, const List& passwdIn)

{

    const List&& balance(std::move(balanceIn));

    const List&& passwd(std::move(passwdIn));

    const List limitCount(makeLeaf(7));

    const function<List(List)> withdraw

     =[balance](const List& amount){

     if(balance>=amount){

         setInsert(balance-amount,balance);

         return(balance);

     }

     return(makeLeaf("Insuffcient funds"));

    };

   

    const function<List(List)> deposit

     =[balance](const List& amount){

     setInsert(balance+amount,balance);

     return(balance);

    };

   

    const function<List(List)> returnErrorMessage

     =[](const List& Dummy){

     return(makeLeaf("Incorrect password"));

    };

    const function<List(List)> returnErrorMonitored

     (makeMonitored(makeLeaf(returnErrorMessage)));

    const function<List(List)> callTheCops

     =[](const List& Dummy){

     return(makeLeaf("The cops are called."));

    };

    const function<function<List(List)>(string,List)> dispatch=

     [withdraw,deposit,returnErrorMonitored,passwd,limitCount,callTheCops]

     (const string passwdInput, const List& message){

     if(!isEq(passwd,makeLeaf(passwdInput))){

         if(returnErrorMonitored

            (makeLeaf("how-many-calls?"))>=limitCount-makeLeaf(1))

             {return(callTheCops);}

         return(returnErrorMonitored);

     }

     returnErrorMonitored(makeLeaf("reset-count"));

     if(isEq(message,makeLeaf("withdraw"))){return(withdraw);}

     if(isEq(message,makeLeaf("deposit"))){return(deposit);}

     cerr<<"Unknown request --- MAKE-ACCOUNT"<<endl;

     exit(1);

     return(function<List(List)>([](const List& i){return(makeList());}));

    };

    return(dispatch);

}

int main(int argc, char** argv)

{

    cout<<"Excersize 3.3:"<<endl;

    const auto acc(makeAccount(makeLeaf(100),makeLeaf("secret-password")));

    cout<<"((acc 'secret-password 'withdraw) 40) = "

     <<listString(acc(string("secret-password"),

                      makeLeaf("withdraw"))(makeLeaf(40)))<<endl;

    cout<<"((acc 'some-other-password 'deposit) 40) = "

     <<listString(acc(string("some-other-password"),

                      makeLeaf("deposit"))(makeLeaf(40)))<<endl;

    cout<<endl<<"Excersize 3.4:"<<endl;

    cout<<"((acc 'secret-password 'withdraw) 40) = "

     <<listString(acc(string("secret-password"),

                      makeLeaf("withdraw"))(makeLeaf(40)))<<endl;

    for(int i=0;i<8;++i){

     cout<<"((acc 'some-other-password 'deposit) 40) = "

         <<listString(acc(string("some-other-password"),

                          makeLeaf("deposit"))(makeLeaf(40)))<<endl;

    }

    cout<<"((acc 'secret-password 'deposit) 40) = "

     <<listString(acc(string("secret-password"),

                      makeLeaf("deposit"))(makeLeaf(40)))<<endl;

    cout<<"((acc 'some-other-password 'deposit) 40) = "

         <<listString(acc(string("some-other-password"),

                          makeLeaf("deposit"))(makeLeaf(40)))<<endl;

   

    return(0);

}

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出力

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Excersize 3.3:

((acc 'secret-password 'withdraw) 40) = 60

((acc 'some-other-password 'deposit) 40) = Incorrect password

Excersize 3.4:

((acc 'secret-password 'withdraw) 40) = 20

((acc 'some-other-password 'deposit) 40) = Incorrect password

((acc 'some-other-password 'deposit) 40) = Incorrect password

((acc 'some-other-password 'deposit) 40) = Incorrect password

((acc 'some-other-password 'deposit) 40) = Incorrect password

((acc 'some-other-password 'deposit) 40) = Incorrect password

((acc 'some-other-password 'deposit) 40) = Incorrect password

((acc 'some-other-password 'deposit) 40) = The cops are called.

((acc 'some-other-password 'deposit) 40) = The cops are called.

((acc 'secret-password 'deposit) 40) = 60

((acc 'some-other-password 'deposit) 40) = Incorrect password