Numerical value of a string

[farah727rash]

Hi all,

I am trying to find the numerical value of a string that stores a two
digit number. I have found the numerical value of a char as:

char character;
cin >character;
int number = character - 48; // Computing the numberical value of
character entered
cout << "The number you entered is: " << number << endl << endl;

How do I do the same and find the numerical value of a string storing 2
digits? I know a way to do this using character arrays:
for ( ; *str != '\0' ; str++)
num = (num * 10) + (*str - 48);

But, I am not supposed to use if statements, character arrays,
apstrings, or atoi in this program.

I am stumped. Any ideas?

Thanks,
Farah.

[mlimber]

fa**********@gmail.com wrote:

I am trying to find the numerical value of a string that stores a two
digit number. I have found the numerical value of a char as:

char character;
cin >character;
int number = character - 48; // Computing the numberical value of
character entered
cout << "The number you entered is: " << number << endl << endl;

How do I do the same and find the numerical value of a string storing 2
digits? I know a way to do this using character arrays:
for ( ; *str != '\0' ; str++)
num = (num * 10) + (*str - 48);

But, I am not supposed to use if statements, character arrays,
apstrings, or atoi in this program.

I am stumped. Any ideas?

See this FAQ:

http://www.parashift.com/c++-faq-lit....html#faq-39.2

Cheers! --M

[Tom Smith]

mlimber wrote:

fa**********@gmail.com wrote:

>I am trying to find the numerical value of a string that stores a two
digit number.

See this FAQ:

http://www.parashift.com/c++-faq-lit....html#faq-39.2

Cheers! --M

Before c.l.c++ I had never seen a group whose FAQs were quite so FA, if you see
what I mean... This one seems to come up every 2 days, along with "I need to
write a dynamic array". I actually discovered the group through the FAQ, which
is still pretty much my first point of reference when something won't work.

Tom

[farah727rash]

But, I am not supposed to use if statements, character arrays,
apstrings, or atoi in this program. That's why I can't hit on any other
way to do this.

On Oct 13, 9:58 am, "mlimber" <[e-mail]:

[e-mail] wrote:

I am trying to find the numerical value of a string that stores a two
digit number. I have found the numerical value of a char as:

char character;
cin >character;
int number = character - 48; // Computing the numberical value of
character entered
cout << "The number you entered is: " << number << endl << endl;

How do I do the same and find the numerical value of a string storing 2
digits? I know a way to do this using character arrays:
for ( ; *str != '\0' ; str++)
num = (num * 10) + (*str - 48);

But, I am not supposed to use if statements, character arrays,
apstrings, or atoi in this program.

I am stumped. Any ideas?See this FAQ:

http://www.parashift.com/c++-faq-lit...sues.html#faq-...

Cheers! --M

[Rolf Magnus]

fa**********@gmail.com wrote:

Hi all,

I am trying to find the numerical value of a string that stores a two
digit number. I have found the numerical value of a char as:

char character;
cin >character;
int number = character - 48; // Computing the numberical value of
character entered

The result of this is implementation-defined. A portable version would be:

int number = character - '0';

You should also add some error handling.

cout << "The number you entered is: " << number << endl << endl;

How do I do the same and find the numerical value of a string storing 2
digits? I know a way to do this using character arrays:
for ( ; *str != '\0' ; str++)
num = (num * 10) + (*str - 48);

But, I am not supposed to use if statements, character arrays,
apstrings, or atoi in this program.

I am stumped. Any ideas?

I have no idea what "apstrings" are, but you could use a stringstream, like:

char character;
std::stringstream stream;
std::cin >character;
stream << character;
std::cin >character;
stream << character;
int number;
stream >number;

(add some error handling)

[LR]

fa**********@gmail.com wrote:

Please don't top post.

But, I am not supposed to use if statements,

What about while or for?

character arrays,

apstrings, or atoi in this program. That's why I can't hit on any other
way to do this.

apstrings? Is this the thing that was written a few years ago for the
AP comp sci test? Not part of standard C++.

>
On Oct 13, 9:58 am, "mlimber" <[e-mail]:

>>[e-mail] wrote:

>>>I am trying to find the numerical value of a

>>>>string

Let's consider the word string. If in fact you're supposed to do this,
then perhaps you are supposed to use the std::string class? If not,
then perhaps the problem is misleadingly worded?

Have you looked into std::istringstream?

>>>>that stores a two
digit number. I have found the numerical value of a char as:

>>>char character;
cin >character;
int number = character - 48; // Computing the numberical value of

Might
const int number = character - '0';
be better?

Shouldn't you check to see if the number is a digit before you do that?

>>>character entered
cout << "The number you entered is: " << number << endl << endl;

>>>How do I do the same and find the numerical value of a string storing 2
digits? I know a way to do this using character arrays:
for ( ; *str != '\0' ; str++)
num = (num * 10) + (*str - 48);

Where I assume that you had something like:
char str[BIGENOUGH];

How did you plan on putting decimal digits into str?

>>>But, I am not supposed to use if statements, character arrays,
apstrings, or atoi in this program.

Why not?

LR

[Ron Natalie]

>
I have no idea what "apstrings" are, but you could use a stringstream, like:

apstrings were part of some classes that the Computer Science AP test
used up until they switched the programming tasks to Java around 2003.
They ap* classes were horrendous and not intended to be used other
than for teaching purposes for the test.

[David Harmon]

On 13 Oct 2006 07:42:44 -0700 in comp.lang.c++, "fa**********@gmail.com" <fa**********@gmail.comwrote,

>But, I am not supposed to use if statements, character arrays,
apstrings, or atoi in this program. That's why I can't hit on any other
way to do this.

Do you have a list of things you _are_ supposed to use, or has your instructor got his head [censored]? How about strtol(), sscanf()
or std::istringstream?

int a(char *c, int v) {
return *c?a(c+1,v*10+(*c-'0')):v;
}

int main(int ac, char** av)
{
for(int ax=1; ax<ac; ++ax)
cout << a(av[ax],0) << '\n';
}

[Bo Yang]

fa**********@gmail.com wrote:

Hi all,

I am trying to find the numerical value of a string that stores a two
digit number. I have found the numerical value of a char as:

char character;
cin >character;
int number = character - 48; // Computing the numberical value of
character entered
cout << "The number you entered is: " << number << endl << endl;

How do I do the same and find the numerical value of a string storing 2
digits? I know a way to do this using character arrays:
for ( ; *str != '\0' ; str++)
num = (num * 10) + (*str - 48);

But, I am not supposed to use if statements, character arrays,
apstrings, or atoi in this program.

I think you can use the boost::lexical_cast

std::string ch ;
cin >ch ;
int number = boost::lexical_cast<int>(ch) ;

It is just simple !