converting variables

[Nate]

I am working on an Oakley parser and want to call an fopen function to
read in the log file. I can use this to read the file, but only if I
pass a "const char" variable to fopen. Since I would like the end
user to specify the name of the log file, I have a scanf in there to
allow the user to do so, but it isn't a const at that point. I have
seen reference to calls like static_cast, dynamic_cast and
reinterpret_cas t in C that will allow me to convert to another type,
but I am having a little trouble using them.

This is what I tried, with no luck:

printf("Enter the log file name: ");

scanf ("%c", &filename);

reinterpret_cas t <const char>( filename );

and get this error:

OakleyParser.cp p(14) : error C2440: 'reinterpret_ca st' : cannot
convert from 'char' to 'char'

So VS.Net recognizes both as Char, but to use the char variable
‘filename' in fopen, I have to have a constant.

file_in = fopen(filename, "r");

OakleyParser.cp p(20) : error C2664: 'fopen' : cannot convert parameter
1 from 'char' to 'const char *'

Any ideas?

[Case]

Nate wrote:

I am working on an Oakley parser and want to call an fopen function to
read in the log file. I can use this to read the file, but only if I
pass a "const char" variable to fopen. Since I would like the end
user to specify the name of the log file, I have a scanf in there to
allow the user to do so, but it isn't a const at that point. I have
seen reference to calls like static_cast, dynamic_cast and
reinterpret_cas t in C that will allow me to convert to another type,

No those're C++ (C-plus-plus) things. Repost your question in the
appropriate newsgroup.

Case

[Neil Cerutti]

In article <7a************ **************@ posting.google. com>,
Nate wrote:

I am working on an Oakley parser and want to call an fopen
function to read in the log file. I can use this to read the
file, but only if I pass a "const char" variable to fopen.
Since I would like the end user to specify the name of the log
file, I have a scanf in there to allow the user to do so, but
it isn't a const at that point. I have seen reference to calls
like static_cast, dynamic_cast and reinterpret_cas t in C that
will allow me to convert to another type, but I am having a
little trouble using them.

You do not need to cast it. It's OK to pass an unqualified
pointer to a function expecting a const pointer.

--
Neil Cerutti
"The barbarian seated himself upon a stool at the wenches side, exposing
his body, naked save for a loin cloth brandishing a long steel broad
sword..." --The Eye of Argon

[kal]

na**@nateharris .com (Nate) wrote in message news:<7a******* *************** ****@posting.go ogle.com>...

printf("Enter the log file name: ");

scanf ("%c", &filename);
You need to give more space between "printf" and "scanf". They keyboard
operator will take some time to enter the information. The slower the
operator the more space should be given between the lines.
scanf ("%c", &filename);

reinterpret_cas t <const char>( filename );
Again, you need to give more space between these two.
It is like reinterpreting history. First you should let a few years
pass before current events become history and then you can reinterpret it.
and get this error:

OakleyParser.cp p(14) : error C2440: 'reinterpret_ca st' : cannot
convert from 'char' to 'char'
reinterpret_cas t is meant to change the _data type_ and not qualifiers.
const is a data qualifier. Try looking up "const_cast ".
So VS.Net recognizes both as Char, but to use the char variable
?filename' in fopen, I have to have a constant.
You should be able to pass a (char *) to a function expectng
(const char *) but not the other way around.
Any ideas?

Throw away the program and go FISHING!

[Mitchell]

On 18 May 2004 09:35:22 -0700, na**@nateharris .com (Nate) wrote:

printf("Enter the log file name: ");

scanf ("%c", &filename);

reinterpret_cas t <const char>( filename );

How did you declare filename?

char filename[1024];

or something similar? In this case, your scanf line should read

scanf("%s",file name);

because filename is already the address of the character array.
&filename points to the sky. Also, use %s !!!!! %c is for reading in a
character.
OakleyParser.c pp(14) : error C2440: 'reinterpret_ca st' : cannot
convert from 'char' to 'char'
a=reinterpret_c ast<char>(x);

is c++'s way of saying

a=(char) x;

for nonpolymorphic types.
So VS.Net recognizes both as Char, but to use the char variable
‘filename' in fopen, I have to have a constant.

file_in = fopen(filename, "r");

Oh, there's no need! =) Just feed it a char. It will be implicitly
casted to const char.

cheers!

[Nick Keighley]

na**@nateharris .com (Nate) wrote in message news:<7a******* *************** ****@posting.go ogle.com>...

first decide which language you are programming in C or C++. C has no
reinterpret_cas t and a C++ program would be unlikely to use scanf() or
fopen(). I'll assume you want to do this in C.

I am working on an Oakley parser and want to call an fopen function to
read in the log file. I can use this to read the file, but only if I
pass a "const char" variable to fopen.
note: that's "const char *". In fact it will accept a "char *"
argument. (the "const" is a promise that the function won't modify the
argument).
Since I would like the end
user to specify the name of the log file, I have a scanf in there to
allow the user to do so, but it isn't a const at that point. I have
seen reference to calls like static_cast, dynamic_cast and
reinterpret_cas t in C that will allow me to convert to another type,
but I am having a little trouble using them.
it isn't necessary
This is what I tried, with no luck:

printf("Enter the log file name: ");
scanf ("%c", &filename);
what is filename? It should an array of char.

char filename [1024];
...
scanf ("%s", filename);

or better, avoid scanf() (its error recovery is poor) and use fgets()
(you'll have to check for '\n' and embedded spaces.
reinterpret_cas t <const char>( filename );

and get this error:

OakleyParser.cp p(14) : error C2440: 'reinterpret_ca st' : cannot
convert from 'char' to 'char'
don't do this.
So VS.Net recognizes both as Char, but to use the char variable
?filename' in fopen, I have to have a constant.

file_in = fopen(filename, "r");

OakleyParser.cp p(20) : error C2664: 'fopen' : cannot convert parameter
1 from 'char' to 'const char *'
it's not the "const" that's the problem. Declare filename correctly
and all your problems go away.
Any ideas?

don't confuse char* with char
--
Nick Keighley

[Mabden]

"Nick Keighley" <ni***********@ marconi.com> wrote in message
news:8a******** *************** ***@posting.goo gle.com...

na**@nateharris .com (Nate) wrote in message news:<7a******* *************** ****@posting.go ogle.com>...

or better, avoid scanf() (its error recovery is poor) and use fgets()
(you'll have to check for '\n' and embedded spaces.

What's wrong with embedded spaces?

--
Mabden

[CBFalconer]

Mabden wrote:

"Nick Keighley" <ni***********@ marconi.com> wrote in message

na**@nateharris .com (Nate) wrote in message

or better, avoid scanf() (its error recovery is poor) and use
fgets() (you'll have to check for '\n' and embedded spaces.)

What's wrong with embedded spaces?

from N869, conversion specifiers for fscanf:

s Matches a sequence of non-white-space
characters.228)

--
Chuck F (cb********@yah oo.com) (cb********@wor ldnet.att.net)
Available for consulting/temporary embedded and systems.
<http://cbfalconer.home .att.net> USE worldnet address!

[Nick Keighley]

"Mabden" <ma****@sbcglob al.net> wrote in message news:<qH******* *********@newss vr27.news.prodi gy.com>...

"Nick Keighley" <ni***********@ marconi.com> wrote in message
news:8a******** *************** ***@posting.goo gle.com...

na**@nateharris .com (Nate) wrote in message

news:<7a******* *************** ****@posting.go ogle.com>...

or better, avoid scanf() (its error recovery is poor) and use fgets()
(you'll have to check for '\n' and embedded spaces.

What's wrong with embedded spaces?

the scanf() solution won't have embedded spaces (as someone else pointed out
%s stops at the first whitespace). Whilst fgets() reads the whole line (or
as much of it as it has room for) including spaces. I was hinting that
fgets() isn't identical to scanf(). In a real program you might to check
it's a valid filename (control characters allowed?). It depends on your OS
what's allowed and what is sensible.
--
Nick Keighley

[Mabden]

"Nick Keighley" <ni***********@ marconi.com> wrote in message
news:8a******** *************** ***@posting.goo gle.com...

"Mabden" <ma****@sbcglob al.net> wrote in message news:<qH******* *********@newss vr27.news.prodi gy.com>...

"Nick Keighley" <ni***********@ marconi.com> wrote in message
news:8a******** *************** ***@posting.goo gle.com...

na**@nateharris .com (Nate) wrote in message

news:<7a******* *************** ****@posting.go ogle.com>...

or better, avoid scanf() (its error recovery is poor) and use fgets()
(you'll have to check for '\n' and embedded spaces.

What's wrong with embedded spaces?

the scanf() solution won't have embedded spaces (as someone else pointed

out %s stops at the first whitespace). Whilst fgets() reads the whole line (or
as much of it as it has room for) including spaces. I was hinting that
fgets() isn't identical to scanf(). In a real program you might to check
it's a valid filename (control characters allowed?). It depends on your OS
what's allowed and what is sensible.

But, but, but ... doesn't everyone just use Windows...?

We love embedded spaces.

Spaces add... space.

Oh, I guess when you talk about a "real program" you mean something that
runs on VAX or DOS, or some other uppercase OS...

--
Mabden
I'm not a troll, but I play one on TV.