Re: Accessing members of template class

From:
Lucas Kanebley Tavares <lucaskt@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Tue, 13 May 2008 12:47:23 -0700 (PDT)
Message-ID:
<94d707de-f1a6-4476-b539-a61baf599fd8@l64g2000hse.googlegroups.com>
Thank you both for the replies, that is now solved.

Regarding the posting, I put the underscores in because I thought
they'd help. As for posting the complete codes, those classes are 100+
lines each, and I thought it might upset people and would break
guideline #3 - Post minimal code (which I had never read, but was
common sense). Next time, I'll try to keep code to a minimum while,
providing a compilable one.

and BTW
typedef typename std::map<ds_node, bool> old_nodes;
doesnt need typename
typedef std::map<ds_node, bool> old_nodes;
typename is used for expressions that are dependent types, and only in
templates.


Heh, I actually added it right before I was posted the code here, just
to rule that out. There wasn't that type name there before :P. Thanks
for the final tip though, I didn't know it'd only be useful around
templates.

Lucas

PS: Ugh, almost top-posted. Not used to posting here! heh

On 13 maio, 16:35, red floyd <no.s...@here.dude> wrote:

Lucas Kanebley Tavares wrote:

Ok, I found a lot of similar errors to this on the net (and here), but
none just like it.

What I have is a bunch of classes that define a few members, for
isntance:

class ds_node {
____public:
________typedef typename std::map<ds_node, bool> old_nodes;
________static ds_node *first(fsm_core &m);
________static ds_node *next(fsm_core &m, ds_node &node, int input);
 ..... (a bunch of stuff goes here) ...
};

and another templated class which is suppose to use those previously
defined classes.

template <class T>
class suc_tree {
____public:
____void run(fsm_core &m);
 ....
};

template <class T>
void suc_tree<T>::run(fsm_core &m) {
____T::old_nodes old_node;

____T *cur = T::first(m);
 .....
}

and I was wondering if this is doable without using inheritance and/or
what would be the suggested methods to go about doing this. The error
I'm getting is:
suctree.hpp|47|error: expected `;' before "old_node" (line 47 =
old_node declaration).
suctree.hpp|64|error: `old_node' was not declared in this scope (line
64 = old_node first use)

After that I get a LOT of STL related errors, but I suppose that once
these are fixed they'll go away. And as I get no errors from calling
first or next, I suppose that I shouldn't get any while declaring
old_node.


Your cut&paste really bad, with the leading underscores, and you didn't
follow FAQ 5.8
(http://www.parashift.com/c++-faq-lite/how-to-post.html#faq-5.8), by
posting complete compileable (except for the error) code.

However, this is a fairly common error (FAQ 35.18 --http://www.parashift.com/c++-faq-lite/templates.html#faq-35.18)

old_nodes is a *dependent* name -- to wit, the compiler can't know that
it's a type without some help from you. Change the line in question to:

typename T::old_nodes old_node;

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