使用e时没有空格,程序会出现奇怪的崩溃

我有一个很奇怪的问题。程序应该将输入的值转换为米,找出最大值和最小值,求和,最后打印所有信息。它似乎在任何情况下都有效,除非我添加一个以e为单位的值,没有空格。例如,如果我按5“enter”e,它会工作,但如果我输入5e,它会完全崩溃。它不会对其他“错误”单元执行此操作。e有什么特别的地方吗?(本程序是为Stroustrup编程手册中的第4章演练编写的)。

        #include<algorithm>
        #include<cmath>
        #include<iostream>
        #include<string>
        #include<vector>
        using namespace std;
        inline void keep_window_open() {char ch; cin >> ch;}


        double cm_m(double x) //cm to m
        {
            return x/100;   
        }
        double in_m(double x) //in to m
        {
            return (x*2.54)/100.0;
        }
        double ft_m(double x) //ft to m
        {
            return (((x*12))*2.54)/100;
        }

        int main()
        {
            int z=0;
            double init=0;
            int w=1;
            string unit;
            double sum=0;
            cout << "Enter an value and a unit (cm,m,in,ft) (To end the program, enter a value with 'd' as the unit. Avoid entering a unit of 'e' without a space.):\n";

            double val1=0;
            double val2=0;
            while(w==1)
            {
                cin >> init >> unit;
                if(unit!="m" && unit!="cm" && unit!="ft" && unit!="in" && unit!="d" ) //rejects unwanted units
                {
                    while(unit!="m" && unit!="cm" && unit!="ft" && unit!="in" && unit!="d")
                    {
                        cout << "Incorrect unit. Please enter a correct unit (m,cm,ft,in):\n";
                        cin >> unit;
                    }
                }
                if(unit=="m")
                {
                    cout << "\n" << init << "m\n";
                }
                if(unit=="cm")
                {
                    init=cm_m(init);
                    cout << "\n" << init << "m\n";
                }
                if(unit=="ft")
                {
                init=ft_m(init);
                cout << "\n" << init << "m\n";
                }
                if(unit=="in")
                {
                init=in_m(init);
                cout << "\n" << init << "m\n";
                }
                if(unit=="d") //d for "done"
                {
                    cout << "\nThe smallest number was: " << val2
                        << "\nThe largest number was: " << val1
                        << "\nThe sum of all numbers entered was: " << sum;
                        keep_window_open();
                        return 0;       
                }

                sum=init+sum;

                while(z<1) //This is set up so this 'while' loop is only used once to give initial values to val1 and val2
                {
                    cout << "\nSmallest so far." << '\t' << "Largest so far.\n";
                    val1=init;
                    val2=init;
                    ++z;
                }   
                if(init > val1)
                {
                    cout << "Largest so far.\n";
                    val1=init;
                }
                else if (init < val2)
                    {
                        cout << "Smallest so far.\n";
                        val2=init;
                    }
            }
        }