Re: [Dev-C++] Demystifying namespace
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Re: [Dev-C++] Demystifying namespace
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From: Per W. <pw...@ia...> - 2003-12-19 01:41:59
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1)
Please. Take as a custom to always use ALL CAPS when #define symbols. It
is practically impossible to read the code if you don't. Since a #defined
symbol might be just about any type of expansion it is really important
when reading the code.
2)
Since a #defined symbol is a preprocessor construct, they are never - I
repeat NEVER - inside any namespace. If the compiler have seen the
#define, and it hasn't been terminated by an #undefine, it will be used.
The compiler complains, since you try jme::file, jme::line, ... where file
and line are #defines.
When you write jme::file it represents jme::__FILE__ which is expanded to
jme::"filename" which isn't a valid construct.
/Per W
On Thu, 18 Dec 2003, Maya wrote:
> Ok, see that there are a few misunderstandings here. I know that using
> the preprocessor '#define' means kind of "replace", so in my statement
> '#define line __LINE__' what I am saying is: the next time I use
> 'line' what I really mean is '__LINE__', but in my rush to finish the
> program I started to treat 'line' as a variable, i.e. std::cout <<
> jme::line << std::endl which of course is wrong, that is clear to me now.
>
> I have handed in the program at school, and even though it works, I
> still have a lot of questions about 'namespace'. I know what you are
> thinking, ask the teachers! that's what my dad tells me too. Well I
> have, but the teachers in my high school are too preoccupied with the
> Christmas stuff to explain it in way that makes sense to ME and not only
> to THEM. I mean. So, any help from you guys will be appreciated.
>
> Please don't be rude if I ask questions that are very simple to you, and
> above all, don't take me wrong if I say something that might sound
> insulting; it is never my intention to be rude to anyone.
> I share my email with my dad; he was really P.O. about some guy wring
> obscenities to me. I mean, think about what would you feel if someone
> starts using that kind of language with your kids, eh!
>
> Hava a good Ho Ho Ho
>
> This class is part of a program I wanted to hand in at school, but as we
> all know
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> =3D=3D=3D GCC =3D=3D=3D
> namespace jme {
>
> #define method __PRETTY_FUNCTION__
> #define file __FILE__
> #define line __LINE__
> #define function __func__
>
> enum error_t{
> //Generic error codes
> msg, //Default message
> warning, //Warning
> fatal, //Display fatal and exit
> .....
> };
> class Exception{
> protected:
> error_t error;
> std::string File, Method;
> size_t Line;
>
> public:
> //Setters
> void setException( jme::error_t, e // Error code
> const std::string&, fn // File name
> const std::string&, m // Method
> size_t l) // Line
> { error =3D e; File =3D fn; Method =3D m; Line =3D l; }
>
> };// Exception
> } // namespace
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> --- Someprogram.H -----
> namespace jme{
> class SomepogramEx : virtual public jme::Exception{
> public:
> SomeprogramEx(error_t ec, const std::string& f,
> const std::string& m, size_t l);
> };//End of SomeprogramEx
> class Someprogram{
> std::string* str_example;
> public:
> Someprogram(){
> try{str_example =3D new std::string;}
> catch(std::bad_alloc& x){
> // This works!!!!
> throw jme::SomeprogramEx(msg, file,
> method, line);
> // This doesn't ?????
> throw jme::SomeprogramEx(jme::msg,
> jme::file, jme::method, jme::line);
> }
> }
> }; //Someprogram
> } // namespace
>
> ce...@te... wrote:
>
> > Yeah, I understand that perfectly.
> > I understood the last maya's question as "passing them (__func__ and
> > __line__) to a srting!!!??? What you say passes the value, I wanted to
> > pass the variable name*". The answer, is that her code, was intending
> > to do just that an std:string variable to which a __func__ or
> > __liner__ were to be passed..
> > It was like her was thinking that when passing the #defined name for
> > them the item passed to her string variables where something like the
> > name of the "definition" variable, which has no sense. Hum, in that
> > moment I saw that sense of her question clearly, know, I wonder if I
> > really understood her question.
> >
> > And yes, the errors should appear there, but I've noticed mingw has
> > some tendency to point the errors related to #defined thing in the
> > next lines; and thos related to missing ';' in headers to the begining
> > of the source file which includes the header.
> >
> > Thanks.
> >
> > P.S. - The high cross-posting comes from her message, I simply clicked
> > 'reply all'
> >
> > *which translated to code, say
> > __line__ =3D "this is the line blah" (sorry if this has no sense, but
> > I'd never used this);
> > She thinks,
> > if #define foo __line__
> > std::string yuu =3D foo; ----> yuu =3D "__line__" (which makes no sense=
)
> > instead of "this is the line blah".
> >
> > Lars Hallberg wrote:
> >
> >> Carlos Garc=EDa del Monte wrote:
> >>
> >>> For what I see, your code is doing exactly the same, but without
> >>> using those #defines
> >>
> >>
> >>
> >>
> >> The strange thing is that You get the error in the std::cout. You
> >> suposed tho get them erlier.
> >>
> >> #define declare preprosessor constant ('dumb' text string constants)
> >> that is global, they shuld not care about scope. They are replaced
> >> litary as text. Your code:
> >>
> >> std::string f =3D foo::file;
> >> size_t l =3D foo::line;
> >>
> >> Transforme to:
> >>
> >> std::string f =3D foo::__func__;
> >> size_t l =3D foo::__LINE__;
> >>
> >> or rather, the value of thes 'special' constants at the #define. The
> >> compile shuld likely find errors there :-/
> >>
> >> Maya:s code actuly declare thes constants as 'real' constants in the
> >> scoop foo, shuld make all the differens!
> >>
> >> PS Litle *too* much crosposting this, is it not? DS
> >>
> >> HTH /LaH
> >>
> >>>
> >>> Maya wrote:
> >>>
> >>>> I want to replace the word __func__ with the word file, and you are
> >>>> telling me to assign the value of __func__ to the std::string
> >>>> variable?
> >>>
> >>>
> >>
> >
> >
> >
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>
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