在 std::stoi 比较字节 0x90 上发现错误

Question

I was coding using on C++ with the compiled MSVC and noticed something:

When I Write some stuff like:

if ( std::stoi ( "4D", nullptr, 16 ) == '\x4D' )
                Beep ( 200, 400 );

I can hear the Beep, but when I write something like:

if ( std::stoi ( "90", nullptr, 16 ) == '\x90' )
            Beep ( 200, 400 );

The comparison doesn't activate the Beep.

I Searched in many places but didn't find any way to resolve this.

Answer 1

stoi() returns an int , not a char . Use 0x4D instead of '\x4D' , and 0x90 instead of '\x90' :

if ( std::stoi ( "4D", nullptr, 16 ) == 0x4D )
    Beep ( 200, 400 );

if ( std::stoi ( "90", nullptr, 16 ) == 0x90 )
    Beep ( 200, 400 );