Tony@dontEmail.com (Tony) wrote:
>
>Is there a mechanism within Standard C++ (incl. the standard C++ libraries)
>for conversion of a 'string' to an 'int', 'float', or some other numeric?
>Something along the lines of:
>
>int myInt = myString.parseInt();

I've seen several suggestions for stringstreams.

Another possibility is good old strtol() and strtoul(), which have been
incorporated into the C++ library from the C library.

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In article <74lclk$4jv$1@news.ncal.verio.com>,
  "Tony" <Tony@dontEmail.com> wrote:
>
> Is there a mechanism within Standard C++ (incl. the standard C++ libraries)
> for conversion of a 'string' to an 'int', 'float', or some other numeric?

Look up atof() and atoi() in the C++ library.

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#include <string>
#include <sstream>

std::string myString;
float f;
int i;

std::istringstream iss(myString);

iss >> f;

or

iss >> i;

Tony wrote:

> Is there a mechanism within Standard C++ (incl. the standard C++ libraries)
> for conversion of a 'string' to an 'int', 'float', or some other numeric?
> Something along the lines of:
>
> int myInt = myString.parseInt();
>
> or some other similarly OO style method?



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In article <74lclk$4jv$1@news.ncal.verio.com>, Tony@dontEmail.com
says...
>
> Is there a mechanism within Standard C++ (incl. the standard C++ libraries)
> for conversion of a 'string' to an 'int', 'float', or some other numeric?
> Something along the lines of:
>
> int myInt = myString.parseInt();
>
> or some other similarly OO style method?

Use a stringstream:

std::istringstream stream(myString);

stream >> myInt;

stream >> myFloat;

Basically, you can do any sort of extraction from the string that you
can from any other input stream.


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Tony wrote in message <74lclk$4jv$1@news.ncal.verio.com>...
>
>Is there a mechanism within Standard C++ (incl. the standard C++ libraries)
>for conversion of a 'string' to an 'int', 'float', or some other numeric?

Such mechanisms are provided through 'istringstream' (#include <sstream>).

>Something along the lines of:
>
>int myInt = myString.parseInt();
>
>or some other similarly OO style method?


I don't think you can do it contextually to a declaration, since streams
don't have method returning values (int, etc) as their results, but, rather,
operator>>, which takes the value to set (int, etc) by reference.  I.e.:

    int myInt;
    istringstream(myString) >> myInt;

It is, of course, easy to provide an inline wrapper template if you're
really keen to get a value-returning function:

    template<typename to>
    inline to parse(const string& str) {
        to t;
        istringstream(str)>>t;
        return t;
    }

    int myInt = parse<int>(myString);

Named-return-value optimization should hopefully make this
as efficient as one would wish.

Using a wrapper template also makes it easy and convenient
to throw an exception on bad-conversion, which streams don't
do by default in the Standard C++ library, but one would likely
wish to do in this case (the "naked", unwrapped construct above
does no validity checking at all on the string->int parsing).


Alex




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Is there a mechanism within Standard C++ (incl. the standard C++ libraries)
for conversion of a 'string' to an 'int', 'float', or some other numeric?
Something along the lines of:

int myInt = myString.parseInt();

or some other similarly OO style method?

Thanks,
Tony



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