cast string to size_t

[pkirk25]

I have a string with format "0|first_name|l ast_name|..." which i can
split to a vector<stringby the "|" token.

At the moment to get the row number I'm using size_t row_number =
atoi(buf_string[0].s_scr()) which throws warnings.

What is the correct way to convert a string "2" to size_t 2?

Thanks in advance.

[ondra.holub]

#include <sstream>

std::istringstr eam iss("a");
size_t size;
iss >size;

You can check whether conversion failed by calling iss.fail()

[ondra.holub]

You should replace parameter of std::istringstr eam iss("a") with a
value you want to convert.

[benben]

pkirk25 wrote:

I have a string with format "0|first_name|l ast_name|..." which i can
split to a vector<stringby the "|" token.

At the moment to get the row number I'm using size_t row_number =
atoi(buf_string[0].s_scr()) which throws warnings.

I am guessing what you mean by s_scr() is in fact c_str(). If my guess
is correct then the following should get you a number

size_t row_number = size_t(atoi(buf _string[0].c_str()));

Notice the int-to-size_t conversion (not a cast.)

>
What is the correct way to convert a string "2" to size_t 2?

Thanks in advance.

Ben

[pkirk25]

Thanks.

Is sstream preferred to atoi?

[Pete Becker]

benben wrote:

>
size_t row_number = size_t(atoi(buf _string[0].c_str()));

Notice the int-to-size_t conversion (not a cast.)

Huh? It's a cast.

--

-- Pete
Roundhouse Consulting, Ltd. -- www.versatilecoding.com
Author of "The Standard C++ Library Extensions: a Tutorial and
Reference." For more information about this book, see
www.petebecker.com/tr1book.

[Pete Becker]

pkirk25 wrote:

Thanks.

Is sstream preferred to atoi?

By some people, not by others.

--

-- Pete
Roundhouse Consulting, Ltd. -- www.versatilecoding.com
Author of "The Standard C++ Library Extensions: a Tutorial and
Reference." For more information about this book, see
www.petebecker.com/tr1book.

[Nate Barney]

pkirk25 wrote:

Is sstream preferred to atoi?

std::stringstre am is much more general than atoi. If you use atoi for
your problem, you'll be limited to the range of values that fit into an
int, whether or not you store the value in a size_t.

Also, atoi gives you no indication whether the string you passed to it
was an invalid string, or whether the string was "0". It returns 0 in
both cases.

Another alternative to atoi, if you don't want to use
std::istringstr eam, is the strtol family, but I don't believe those
functions are actually in the C++ standard. They're in the C99 standard
and a few others, so your compiler may support them.

Nate

[Nate Barney]

Nate Barney wrote:

Another alternative to atoi, if you don't want to use
std::istringstr eam, is the strtol family, but I don't believe those
functions are actually in the C++ standard. They're in the C99 standard
and a few others, so your compiler may support them.

I neglected to mention that boost::lexical_ cast is another good choice
for converting strings to numbers, and it's what I use almost
exclusively for this purpose.

Nate

[Alf P. Steinbach]

* Nate Barney:

Another alternative to atoi, if you don't want to use
std::istringstr eam, is the strtol family, but I don't believe those
functions are actually in the C++ standard.

They are.

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