Re: Pulling my hair out..

From:

"peter koch" <peter.koch.larsen@gmail.com>

Newsgroups:

comp.lang.c++

Date:

12 Feb 2007 06:10:31 -0800

Message-ID:

<1171289431.669799.256380@k78g2000cwa.googlegroups.com>

On Feb 12, 2:35 pm, "Mr. Politics" <mrpolit...@gmail.com> wrote:

On Feb 12, 8:18 am, "Sylvester Hesp" <s.h...@oisyn.nl> wrote:

"Mr. Politics" <mrpolit...@gmail.com> wrote in message

news:1171285778.504960.220640@h3g2000cwc.googlegroups.com...

On Feb 12, 8:05 am, "Mr. Politics" <mrpolit...@gmail.com> wrote:

This function keeps giving me negative values (esp. if I feed it
64,153,160)

What gives?

int quantity(char chrs[],int length)
{
int q = 0;
int x;
int c = 0;

for (x=0; x<length;x++)
{
c = (int)chrs[x];
q += c;
}
return q;
}

char is probably signed on your platform (and with 8 bits, it can possibly
only hold values between -128 and 127 inclusive)

- Sylvester

For posterity, the fix... (Thank you!)

int quantity(unsigned char chrs[],int length)
{
        int q = 0;
        int x;
        int c = 0;

        for (x=0; x<length;x++)
        {
                c = (int)chrs[x];
                q += c;

        }
        return q;

}

Instead of pulling hair out, you should pull your code in to a
debugger and see whats going on. One hint is that "casts are evil" is
almost always true.

/Peter