function flow() view public returns(uint){

        uint8 mm = 255;

        return mm;

    }

function flow() view public returns(uint){

        uint8 mm = 0;

        return mm;

    }

function flow() view public returns(uint){

        uint8 mm = 255;

        mm++;

        return mm;

    }

function flow() view public returns(uint){

        uint8 mm = 0;

        mm--;

        return mm;

    }

function errorTest() returns(int){

        int a = 2;

        int b = 3;

        return a/b;

    }

function errorTest() returns(int){

        int a = 2;

        int b = 0;//不能执行除0操作

        return a/b;

    }

function errorTest3() returns(int){

        int a = 2;

        return a<<-1;

    }

function errorTest4() returns(int){

        int a = 2;

        int b = -1;

        return a<<b;

    }