strtod - Dynamic Memory?

[Marky C]

atof is not working.

double a = atof("12.345");

a gets set to 12.000

I am working on a toshiba micro. The data map has no space allocated
to it for dynamic memory.

Does anyone have an idea? Could it be due to the lack of dynamic
memmor space?

All thoughts gratefully received

Marky C

[Dan Pop]

In <Bo************ ******@newsread 1.news.pas.eart hlink.net> "Mike Wahler" <mk******@mkwah ler.net> writes:

"Marky C" <eg*********@ho tmail.com> wrote in message
news:9e******* *************** ****@posting.go ogle.com...

atof is not working.

double a = atof("12.345");

a gets set to 12.000

If you're using a pre-C99 compiler, and failed
to provide a prototype for 'atof()' (by #including
<stdlib.h>), then the compiler will assume that 'atof()'
returns type 'int'. This fact will truncate the
fractional part of the return value before assigning
it to 'a'.

Think harder. If atof is supposed to return an int, the compiler
will look in the wrong place for the result (e.g. an integer register
instead of a floating point register), or will interpret part of
the representation of the f.p. result as an integer, if the result
is passed in memory (on the stack). No conversion of 12.345 to the
implicitly declared type of atof() is supposed to take place.
A result of 12 can only be explained as a pure accident (and I have
no better explanation).

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Da*****@ifh.de

[Mike Wahler]

"Dan Pop" <Da*****@cern.c h> wrote in message
news:c4******** **@sunnews.cern .ch...

In <Bo************ ******@newsread 1.news.pas.eart hlink.net> "Mike Wahler" <mk******@mkwah ler.net> writes:

"Marky C" <eg*********@ho tmail.com> wrote in message
news:9e******* *************** ****@posting.go ogle.com...

atof is not working.

double a = atof("12.345");

a gets set to 12.000
If you're using a pre-C99 compiler, and failed
to provide a prototype for 'atof()' (by #including
<stdlib.h>), then the compiler will assume that 'atof()'
returns type 'int'. This fact will truncate the
fractional part of the return value before assigning
it to 'a'.

Think harder.

That's too hard. :-)
If atof is supposed to return an int, the compiler
will look in the wrong place for the result (e.g. an integer register
instead of a floating point register), or will interpret part of
the representation of the f.p. result as an integer, if the result
is passed in memory (on the stack). No conversion of 12.345 to the
implicitly declared type of atof() is supposed to take place.
A result of 12 can only be explained as a pure accident (and I have
no better explanation).

You're right, I didn't give the issue enough thought.
I'll blame it on the (unseasonably) nice weather here
today, which has me frequently looking out the window. :-)

-Mike

[David Resnick]

eg*********@hot mail.com (Marky C) wrote in message news:<9e******* *************** ****@posting.go ogle.com>...

atof is not working.

double a = atof("12.345");

a gets set to 12.000

I am working on a toshiba micro. The data map has no space allocated
to it for dynamic memory.

Does anyone have an idea? Could it be due to the lack of dynamic
memmor space?

All thoughts gratefully received

Marky C

Perhaps your program is not running in the "C" locale. In which case the
character that represents the decimal point depends on the locale. As
far as I know, it is always either a '.' or a ',', but that isn't
guaranteed. Example that demonstrates the issue using strtod, which
is preferable to atof:

dresnick(3276)$ cat foo.c
#include <locale.h>
#include <stdlib.h>
#include <stdio.h>

int main(void)
{
printf("%g\n", strtod("12.345" , NULL));
setlocale(LC_NU MERIC, "de_DE");
printf("%g\n", strtod("12.345" , NULL));
printf("%g\n", strtod("12,345" , NULL));
return 0;
}
dresnick(3277)$ gcc -Wall -ansi -pedantic -o foo foo.c
dresnick(3278)$ foo
12.345
12
12,345
-David

[Thomas Stegen]

Marky C wrote:

atof is not working.

double a = atof("12.345");

a gets set to 12.000

If you forget to include a prototype for atof it will
default to return int and as we all know
(double)(int)12 .345 == 12.000 or thereabouts.

Have you included stdlib.h?

--
Thomas.

[Dan Pop]

In <59************ *************@p osting.google.c om> ln********@hotm ail.com (David Resnick) writes:

eg*********@ho tmail.com (Marky C) wrote in message news:<9e******* *************** ****@posting.go ogle.com>...

atof is not working.

double a = atof("12.345");

a gets set to 12.000

I am working on a toshiba micro. The data map has no space allocated
to it for dynamic memory.

Does anyone have an idea? Could it be due to the lack of dynamic
memmor space?

All thoughts gratefully received

Marky C
Perhaps your program is not running in the "C" locale. In which case the
character that represents the decimal point depends on the locale.

Nope:

6 In other than the "C" locale, additional locale-specific subject
^^^^^^^^^^
sequence forms may be accepted.

This means that '.' is accepted in ALL locales, but other locales can also
accept other characters as the "decimal point".
As far as I know, it is always either a '.' or a ',', but that isn't
guaranteed. Example that demonstrates the issue using strtod, which
is preferable to atof:

dresnick(3276) $ cat foo.c
#include <locale.h>
#include <stdlib.h>
#include <stdio.h>

int main(void)
{
printf("%g\n", strtod("12.345" , NULL));
setlocale(LC_NU MERIC, "de_DE");
printf("%g\n", strtod("12.345" , NULL));
printf("%g\n", strtod("12,345" , NULL));
return 0;
}
dresnick(3277) $ gcc -Wall -ansi -pedantic -o foo foo.c
dresnick(3278) $ foo
12.345
12
12,345

Your library is broken in multiple places. The correct output of your
program consists of three *identical* lines because "12.345" is valid
input for strtod in *any* locale and because the current locale does
NOT affect the output of the %g conversion specifier (for reasons
that I do not understand, the Single Unix Specification is at odds
with the C standard here).

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Da*****@ifh.de

[Dan Pop]

In <40********@nnt phost.cis.strat h.ac.uk> Thomas Stegen <ts*****@cis.st rath.ac.uk> writes:

Marky C wrote:

atof is not working.

double a = atof("12.345");

a gets set to 12.000

If you forget to include a prototype for atof it will
default to return int and as we all know
(double)(int)1 2.345 == 12.000 or thereabouts.

So what? There is no (double)(int)12 .345 taking place in this code,
if the implicit declaration of atof is in effect.

BTW, there is no need for a prototype to fix the code, a good old
declaration is enough:

double atof();

But, of course, the *right* fix is to include <stdlib.h>.

Dan
--
Dan Pop
DESY Zeuthen, RZ group
Email: Da*****@ifh.de

[Keith Thompson]

Da*****@cern.ch (Dan Pop) writes:

In <59************ *************@p osting.google.c om>
ln********@hotm ail.com (David Resnick) writes:

[...]

Perhaps your program is not running in the "C" locale. In which case the
character that represents the decimal point depends on the locale.

Nope:

6 In other than the "C" locale, additional locale-specific subject
^^^^^^^^^^
sequence forms may be accepted.

This means that '.' is accepted in ALL locales, but other locales can also
accept other characters as the "decimal point".

No, I don't think it does.

The standard defines the atof function as (nearly) equivalent to a
call to the strtod function.

The description of the strtod function (C99 7.20.1.3) says:

The expected form of the subject sequence is an optional plus or
minus sign, then one of the following:

-- a nonempty sequence of decimal digits optionally containing
a decimal-point character, then an optional exponent part
as defined in 6.4.4.2;

It uses the term "decimal-point character", not "period". A few
paragraphs later, it says:

If the subject sequence has the expected form for a floating-point
number, the sequence of characters starting with the first digit
or the decimal-point character (whichever occurs first) is
interpreted as a floating constant according to the rules of
6.4.4.2, except that the decimal-point character is used in place
of a period, [...]

(The wording in the C90 standard is similar; it's easier to
cut-and-paste from my copy of the C99 standard.)

dresnick(3276) $ cat foo.c
#include <locale.h>
#include <stdlib.h>
#include <stdio.h>

int main(void)
{
printf("%g\n", strtod("12.345" , NULL));
setlocale(LC_NU MERIC, "de_DE");
printf("%g\n", strtod("12.345" , NULL));
printf("%g\n", strtod("12,345" , NULL));
return 0;
}
dresnick(3277) $ gcc -Wall -ansi -pedantic -o foo foo.c
dresnick(3278) $ foo
12.345
12
12,345

Your library is broken in multiple places. The correct output of your
program consists of three *identical* lines because "12.345" is valid
input for strtod in *any* locale and because the current locale does
NOT affect the output of the %g conversion specifier (for reasons
that I do not understand, the Single Unix Specification is at odds
with the C standard here).

The description of the %e and %f conversion specifiers also uses the
term "decimal-point character", not "period". ("%g" is defined in
terms of "%e" and "%f".)

C99 7.1.1p2 says (underscores indicate italics):

The _decimal-point character_ is the character used by functions
that convert floating-point numbers to or from character sequences
to denote the beginning of the fractional part of such character
sequences. It is represented in the text and examples by a
period, but may be changed by the setlocale function.

Again, the wording in the C90 standard is similar.

For locales other than "C", the numeric conversion functions and
formatted I/O functions are not required to recognize '.' as a
decimal-point character.

--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
Schroedinger does Shakespeare: "To be *and* not to be"

[David Resnick]

Da*****@cern.ch (Dan Pop) wrote in message news:<c4******* ****@sunnews.ce rn.ch>...

In <59************ *************@p osting.google.c om> ln********@hotm ail.com (David Resnick) writes:

eg*********@ho tmail.com (Marky C) wrote in message news:<9e******* *************** ****@posting.go ogle.com>...

atof is not working.

double a = atof("12.345");

a gets set to 12.000

I am working on a toshiba micro. The data map has no space allocated
to it for dynamic memory.

Does anyone have an idea? Could it be due to the lack of dynamic
memmor space?

All thoughts gratefully received

Marky C

Perhaps your program is not running in the "C" locale. In which case the
character that represents the decimal point depends on the locale.

Nope:

6 In other than the "C" locale, additional locale-specific subject
^^^^^^^^^^
sequence forms may be accepted.

This means that '.' is accepted in ALL locales, but other locales can also
accept other characters as the "decimal point".

As far as I know, it is always either a '.' or a ',', but that isn't
guaranteed. Example that demonstrates the issue using strtod, which
is preferable to atof:

dresnick(3276) $ cat foo.c
#include <locale.h>
#include <stdlib.h>
#include <stdio.h>

int main(void)
{
printf("%g\n", strtod("12.345" , NULL));
setlocale(LC_NU MERIC, "de_DE");
printf("%g\n", strtod("12.345" , NULL));
printf("%g\n", strtod("12,345" , NULL));
return 0;
}
dresnick(3277) $ gcc -Wall -ansi -pedantic -o foo foo.c
dresnick(3278) $ foo
12.345
12
12,345

Your library is broken in multiple places. The correct output of your
program consists of three *identical* lines because "12.345" is valid
input for strtod in *any* locale and because the current locale does
NOT affect the output of the %g conversion specifier (for reasons
that I do not understand, the Single Unix Specification is at odds
with the C standard here).

Dan

Well, the library (glibc) is behaving as documented for the library.
Guess it isn't conforming to the C-standard. Admittedly, I do have an
older glibc (not sure the version, I'm not at work now). The glibc
docs for strtod say:

....
A floating point number in decimal or hexadecimal format. The decimal
format is:

* A nonempty sequence of digits optionally containing a
decimal-point character--normally ., but it depends on the locale (see
General Numeric).
....

I see that N869 says this isn't correct. The standard says that
strtod needs to take a floating point constant as described by section
6.4.4.2, which does explicitly have the '.' character. And as you
say, locale setting can give it an additional options.

That said, the original poster's issue could be due to a similar
(perhaps the same?) broken library implementation.

-David

[Keith Thompson]

ln********@hotm ail.com (David Resnick) writes:
[...]

Well, the library (glibc) is behaving as documented for the library.
Guess it isn't conforming to the C-standard. Admittedly, I do have an
older glibc (not sure the version, I'm not at work now). The glibc
docs for strtod say:

...
A floating point number in decimal or hexadecimal format. The decimal
format is:

* A nonempty sequence of digits optionally containing a
decimal-point character--normally ., but it depends on the locale (see
General Numeric).
...

I see that N869 says this isn't correct. The standard says that
strtod needs to take a floating point constant as described by section
6.4.4.2, which does explicitly have the '.' character. And as you
say, locale setting can give it an additional options.

I think you're misreading N869. It says:

The expected form of the subject sequence is an optional plus or
minus sign, then one of the following:

-- a nonempty sequence of decimal digits optionally containing
a decimal-point character, then an optional exponent part
as defined in 6.4.4.2;

The phrase "as defined in 6.4.4.2" refers only to the optional
exponent part, not to the entire floating point costant. The fact
that it uses the term "decimal-point character" rather than "period"
makes it clear that it doesn't have to recognize a period. The term
"decimal-point character" is defined in 7.1.1p3:

The _decimal-point character_ is the character used by functions
that convert floating-point numbers to or from character sequences
to denote the beginning of the fractional part of such character
sequences. It is represented in the text and examples by a period,
but may be changed by the setlocale function.

The actual C99 standard has identical wording; the wording in the C90
standard is identical or very similar.

--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
Schroedinger does Shakespeare: "To be *and* not to be"

[Joona I Palaste]

Marky C <eg*********@ho tmail.com> scribbled the following:

atof is not working. double a = atof("12.345"); a gets set to 12.000 I am working on a toshiba micro. The data map has no space allocated
to it for dynamic memory. Does anyone have an idea? Could it be due to the lack of dynamic
memmor space?

Am I the only person who can't understand why the topic is about strtod
but the message is about atof?

--
/-- Joona Palaste (pa*****@cc.hel sinki.fi) ------------- Finland --------\
\-- http://www.helsinki.fi/~palaste --------------------- rules! --------/
"War! Huh! Good God, y'all! What is it good for? We asked Mayor Quimby."
- Kent Brockman