从文件中读取字符串

Question

I've been stuck on this for a while. I'm trying to read a string from a file. The string contains notes (A, G, C, B, etc.) which may be followed by certain values. For example, when a note is followed by '~', the note has added 20 to its duration (A~~ adds 40 to the preset duration). Other possible inputs: A(4) should change the frequency by +4. B# should change the frequency by +20.

The input would look something like this: B(4)~F#(5)~~~Aa

I started by doing the following but I can't seem to figure out how to increment frequency with each additional '~' after a note.

string a;
for (int i = 0; i < a.length(); a++)
{
    if(a.at(i) == 'C')
    {
        frequency = 440;
        duration = 10;

        if(a.at(i++) == '~')
        {
            frequency += 20;
        }
    }
Values(frequency, duration)

}

Answer 1

The point in your loop that checks for a '~' is only reached when a.at(i) == C, and only tests i++. add within the conditional for == '~' a loop:

if(a.at(i++) == '~'){
    while(a.at(i) == '~'){
        frequency += 20;
        i++;
    }
}