string2float

[pontiy.pilat@gmail.com]

How i can convert *char to float?

[Chris McDonald]

Re: string2float

pontiy.pilat@gm ail.com writes:

>How i can convert *char to float?

atof();

--
Chris,

[Eric Sosman]

Re: string2float

Chris McDonald wrote:

pontiy.pilat@gm ail.com writes:
>
>

>>How i can convert *char to float?

>
>
atof();

strtod() is better, but neither actually converts a
string to float: both convert to double. The only way I
can think of to convert directly to float is

if (sscanf(my_stri ng, "%f", &float_variable ) == 1)

--
Eric Sosman
esosman@acm-dot-org.invalid

[Robert Gamble]

Re: string2float


Eric Sosman wrote:

Chris McDonald wrote:
>

pontiy.pilat@gm ail.com writes:

>How i can convert *char to float?

atof();

>
strtod() is better, but neither actually converts a
string to float: both convert to double. The only way I
can think of to convert directly to float is
>
if (sscanf(my_stri ng, "%f", &float_variable ) == 1)

C99 has strtof() which will convert directly to float representation.

Robert Gamble

[Flash Gordon]

Re: string2float

Chris McDonald wrote:

pontiy.pilat@gm ail.com writes:
>

>How i can convert *char to float?

>
atof();

Not a very good choice. You can't test to see if it worked and if the
value cannot be represented as a double it invokes undefined behaviour
(i.e. anything can happen). A far better function to use is strtod. This
allows you to test how much of the string was converted and if it is out
of range behave in a defined manner including setting errno, and thus
you can do error checking reliable and report problems such as the user
entering "fiftythree " of "12e456789" .
--
Flash Gordon
Still sigless on this computer.

[Keith Thompson]

Re: string2float

"Robert Gamble" <rgamble99@gmai l.comwrites:

Eric Sosman wrote:

>Chris McDonald wrote:

pontiy.pilat@gm ail.com writes:
>>How i can convert *char to float?
>
atof();

>>
> strtod() is better, but neither actually converts a
>string to float: both convert to double. The only way I
>can think of to convert directly to float is
>>
> if (sscanf(my_stri ng, "%f", &float_variable ) == 1)

>
C99 has strtof() which will convert directly to float representation.

And if your implementation doesn't have strtof(), it's easy enough to
call strtod() and assign the result to a float. It's even easier to
use double in the first place.

sscanf() has the disadvantage that, if the floating-point literal in
the string represents a value that can't be represented in the target
type, the behavior is undefined. strtod() has well-defined behavior
on overflow. (It would have been nice if sscanf() had been defined
this way as well.)

--
Keith Thompson (The_Other_Keit h) kst-u@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <* <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.

[Robert Gamble]

Re: string2float

Keith Thompson wrote:

"Robert Gamble" <rgamble99@gmai l.comwrites:

Eric Sosman wrote:

Chris McDonald wrote:
pontiy.pilat@gm ail.com writes:
>How i can convert *char to float?

atof();
>
strtod() is better, but neither actually converts a
string to float: both convert to double. The only way I
can think of to convert directly to float is
>
if (sscanf(my_stri ng, "%f", &float_variable ) == 1)

C99 has strtof() which will convert directly to float representation.

>
And if your implementation doesn't have strtof(), it's easy enough to
call strtod() and assign the result to a float.

Except that if the result can be represented as a double but is outside
the range of float then assigning the return value to a float will
result in undefined behavior. In this case one would need to check the
return value of strtod before assigning it to float, which is a pain
and probably why strtof() was added.

It's even easier to use double in the first place.

Agreed.

sscanf() has the disadvantage that, if the floating-point literal in
the string represents a value that can't be represented in the target
type, the behavior is undefined. strtod() has well-defined behavior
on overflow. (It would have been nice if sscanf() had been defined
this way as well.)

Robert Gamble