c++ noob

[baygross@gmail.com]

I am taking an introduction to c++ at my school. We use the
Lawrenceville Press book and studio at my school. I just downloaded
Microsoft Visual Studio 2005 for experimenting away from school.

I am trying to write a function, (with Microsoft Visual Studio), to
turn a string into an integer. The LVP studio has a library, (whos
name a cant recall) that lets me turn a C++ string into a C string,
and then use atoi() to convert it to an integer. Visual Studio, as
far as i can tell, will not let me easily do this.

I have looked at the help file, but to no avail. The help file uses
characters to turn strings into intergers, and it confuses me. What is
the difference between:
string mystring="hello world" and char *mystring ="hello
world" ????


If anyone could give me a link or a simple explination to the
difference between these two types, and/or give me some help on
turning strings into integers, I would really appreciate it.

_BG

[Mike Wahler]

Re: c++ noob


<baygross@gmail .com> wrote in message
news:1131762219 .221245.25210@o 13g2000cwo.goog legroups.com...[color=blue]
>I am taking an introduction to c++ at my school. We use the
> Lawrenceville Press book and studio at my school. I just downloaded
> Microsoft Visual Studio 2005 for experimenting away from school.[/color]

Visual Studio contains so many "bells and whistles"
that it's difficult for the novice to discover the
C++ translator buried deep within.

Try a simpler package, or read the documentation and
learn how to use the compiler from the command line.
[color=blue]
>
> I am trying to write a function, (with Microsoft Visual Studio), to
> turn a string into an integer. The LVP studio has a library, (whos
> name a cant recall) that lets me turn a C++ string into a C string,[/color]

The standard C++ function is a member of the std::string class:
c_str().
[color=blue]
> and then use atoi() to convert it to an integer.[/color]

'atoi()' does do that, but is inherently dangerous.
See the C FAQ for details.
[color=blue]
> Visual Studio, as
> far as i can tell, will not let me easily do this.[/color]

All the components are there, albeit not easy for
a beginner to discern.

Also note that here we only discuss the C++ language,
not particular compiler packages.
[color=blue]
>
> I have looked at the help file, but to no avail.[/color]

A good book on C++ would be a much better alternative.
See the reviews at www.accu.org for ideas and suggestions.
[color=blue]
> The help file uses
> characters to turn strings into intergers, and it confuses me. What is
> the difference between:
> string mystring="hello world" and char *mystring ="hello
> world" ????[/color]

The first creates an object of the C++ standard library
type 'string'. The second creates a pointer object and
stores as its value the address of a string literal.
The string object is modifiable, the string literal
whose address the pointer contains is not (without
undefinded behavior).
[color=blue]
>
>
> If anyone could give me a link or a simple explination to the
> difference between these two types, and/or give me some help on
> turning strings into integers, I would really appreciate it.[/color]

#include <iostream>
#include <sstream>
#include <string>

int main()
{
std::string s("123");
std::istringstr eam iss(s);
int i(0);
iss >> i;
std::cout << i << '\n'; /* prints 123 */
return 0;
}

Alternatively, look up 'std::string::c _str()'
and 'strtol()' (declared by <cstdlib>)

-Mike

[baygross@gmail.com]

Re: c++ noob

thanks for the advice!
-bg

[Greg Comeau]

Re: c++ noob

In article <1131762219.221 245.25210@o13g2 000cwo.googlegr oups.com>,
<baygross@gmail .com> wrote:[color=blue]
>I am taking an introduction to c++ at my school. We use the
>Lawrencevill e Press book and studio at my school. I just downloaded
>Microsoft Visual Studio 2005 for experimenting away from school.
>
> I am trying to write a function, (with Microsoft Visual Studio), to
>turn a string into an integer. The LVP studio has a library, (whos
>name a cant recall) that lets me turn a C++ string into a C string,
>and then use atoi() to convert it to an integer. Visual Studio, as
>far as i can tell, will not let me easily do this.
>
> I have looked at the help file, but to no avail. The help file uses
>characters to turn strings into intergers, and it confuses me. What is
>the difference between:
>string mystring="hello world" and char *mystring ="hello
>world" ????
>
>
>If anyone could give me a link or a simple explination to the
>difference between these two types, and/or give me some help on
>turning strings into integers, I would really appreciate it.[/color]

Check out http://www.comeaucomputing.com/techtalk/#atoi

http://www.comeaucomputing.com/techtalk/#stringtostring

http://www.comeaucomputing.com/techtalk/#stringvsstring

--
Greg Comeau / Celebrating 20 years of Comeauity!
Comeau C/C++ ONLINE ==> http://www.comeaucomputing.com/tryitout
World Class Compilers: Breathtaking C++, Amazing C99, Fabulous C90.
Comeau C/C++ with Dinkumware's Libraries... Have you tried it?