invalid comparison

Hey, I am getting a compiler error that I don't agree with (haha). I am attempting to compare chars, but the error the compiler is giving me is:

Code:

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46 prog6.cpp ISO C++ forbids comparison between pointer and integer

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My code is:

Code:

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int main(int argc, char *argv[])
{

[snip]

if(argv[typeIndex] != 's')
    {
        cerr << "Invalid Type argument '" << argv[typeIndex] << "'.\n";
        exit(1);
    }

}

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If I changed the single quotes around the s to double quotes "s" it compilers, however even if argv[typeIndex] is equal to "s" the error message still appears.

Code:

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Invalid Type argument "s".

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Any ideas?

Well I think I just solved my problem, by changing it to:

Code:

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if(*argv[typeIndex] != 's')

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However, when I try to add to this statement, I get an error, like above when I run the program - even if the argument is 's', it still spits out the error:

Code:

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if((*argv[typeIndex] != 's') || (*argv[typeIndex] != 'b') || (*argv[typeIndex] != 'q'))
    {
        cerr << "Invalid Type argument '" << argv[typeIndex] << "'.\n";
        exit(1);
    }

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It works fine without the OR statements (just the checking for 's')

char *argv[] is the same as char** argv, so what you did is argv[index] == char* and 's' == char, hence the compile error. Both types must be the same types.

argv is an array of strings (char pointers), not of chars.

Quote:

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If I changed the single quotes around the s to double quotes "s" it compilers, however even if argv[typeIndex] is equal to "s" the error message still appears.

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use strcmp to compare strings. What you are doing now is comparing pointers (whether they point to the same address, and they never will)

Any idea why when I put OR statements inside the working if statement that it then no longer works?

Also, any idea as to why I am getting this error?

Code:

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78 Cprog6.cpp [Warning] comparison is always false due to limited range of data type

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Code:

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if(*argv[countIndex] > 32767)
    {
        cerr << "Invalid count argument '" << argv[countIndex] << "'.\n";
        exit(1);
    }

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countIndex would be a value like 4 or 5. If I do (int)argv[countIndex] instead of *, it says that the value is like 53 when argv[countIndex] is actually 32000. I don't understand what is going on.

Let me guess, you are using a DOS based compiler, e.g. Turbo C?

In that case, 32767 is the highest integer value you could get to - so comparing with that will ALWAYS BE FALSE - so it's not much point to make the comparison and have the code inside the if-statement. If you add one, you should get 32768, but it is a negative nunber [-32768] because signed integers use the highest bit to indicate sign.

I seem to remember that Turbo & Borland C/C++ compilers give that error message.

You get the same if you try to comare an unsigned value for "less than zero", as that's also impossible to achieve.

--
Mats

Ah, thanks. Another logic problem that I am stuck on. I have this code:

Code:

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    cout << "\t[" << *argv[seedIndex] << "]\n";

    if(*argv[seedIndex] < 1)
    {
        cerr << "Invalid Seed argument '" << argv[seedIndex] << "'.\n";
        exit(1);
    }

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I run the program so it prints out

Code:

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[0]

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for argv[seedIndex], yet my error message never gets executed - it should, because 0 < 1, but it doesn't, and I don't know why :\

Code:

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if(*argv[countIndex] > 32767)

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Isn't *argv[countIndex] the same as argv[countIndex][0]? In which case you would be comparing a character with a large integer. (A character can have the value of 255 or 127 at most, so any char is always less than 32767.)

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I run the program so it prints out
[0]

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You are printing the ascii character '0' which has an integral value of 48 (or so). Which is very different from character '\0' (integral value 0), which is a non-printing character (you might see a space or something like that).

Edit: Commandline arguments are char arrays. You cannot treat them as integers. If you want to interpret the arguments as integers, you'll first need to convert them into ints, using std::stringstream's or C conversion functions.

Regarding your OR-chain, write out what you're testing and think about it:

If the character is not 's' OR the character is not 'b' OR the character is not 'q'
then print an error message.