Problem with STL

[Lloyd Dupont]

I'm trying a double indirect look-up table for some function pointer in my app (yep, I have good reason).
I'm trying to use std::map for the table but (because of the double indirection) I need to use a "std::map*"
Which I don't know how to map[index] (with a pointer)

Now perhaps I'm misusing it, I'm not sure (I know nothing of STL and I have some problem understanding its header)

Anyway here is my code (problem explained in red), if you could give me some tips.....
==============
static std::map<const char*, SELmap_sels;
static std::map<OClass, std::map<SEL, IMP>*map_imps;

void id::GetImpAlways(const char* name, SEL& sel, IMP& imp)
{
if( !_handle )
throw gcnew ObjectDisposedException(Class()->Name);

if(map_sels.find(name) == map_sels.end())
{
sel = sel_register_name(name);
map_sels[name] = sel;
}
else
{
sel = map_sels[name];
}

std::map<SEL, IMP* class_imps; // here I get the problematic "map *"
if(map_imps.find(_handle->class_pointer) == map_imps.end())
{
class_imps = new std::map<SEL, IMP>();
map_imps[_handle->class_pointer] = class_imps;
}
else
{
class_imps = map_imps[_handle->class_pointer];
}

if(class_imps->find(sel) == class_imps->end())
{
imp = get_imp(_handle->class_pointer, sel);
if( !imp )
throw gcnew ObjectiveCException("No such method");
class_imps[sel] = imp; // can't do that with 'map*', what should I so?
}
else
{
imp = class_imps[sel]; // can't do that with 'map*', what should I so?
}
}
==============

[Lloyd Dupont]

BTW, never mind my problem.
The program crash at the first line: if(map_sels.find(name) == map_sels.end())
How do I do?
I have a home made C hashtable possibly I should use it instead :-/
"Lloyd Dupont" <net.galador@ldwrote in message news:%2****************@TK2MSFTNGP05.phx.gbl...
I'm trying a double indirect look-up table for some function pointer in my app (yep, I have good reason).
I'm trying to use std::map for the table but (because of the double indirection) I need to use a "std::map*"
Which I don't know how to map[index] (with a pointer)

Now perhaps I'm misusing it, I'm not sure (I know nothing of STL and I have some problem understanding its header)

Anyway here is my code (problem explained in red), if you could give me some tips.....
==============
static std::map<const char*, SELmap_sels;
static std::map<OClass, std::map<SEL, IMP>*map_imps;

void id::GetImpAlways(const char* name, SEL& sel, IMP& imp)
{
if( !_handle )
throw gcnew ObjectDisposedException(Class()->Name);

if(map_sels.find(name) == map_sels.end())
{
sel = sel_register_name(name);
map_sels[name] = sel;
}
else
{
sel = map_sels[name];
}

std::map<SEL, IMP* class_imps; // here I get the problematic "map *"
if(map_imps.find(_handle->class_pointer) == map_imps.end())
{
class_imps = new std::map<SEL, IMP>();
map_imps[_handle->class_pointer] = class_imps;
}
else
{
class_imps = map_imps[_handle->class_pointer];
}

if(class_imps->find(sel) == class_imps->end())
{
imp = get_imp(_handle->class_pointer, sel);
if( !imp )
throw gcnew ObjectiveCException("No such method");
class_imps[sel] = imp; // can't do that with 'map*', what should I so?
}
else
{
imp = class_imps[sel]; // can't do that with 'map*', what should I so?
}
}
==============

[Lloyd Dupont]

never mind, I wil use my own C Hashtable...
"Lloyd Dupont" <net.galador@ldwrote in message news:%2****************@TK2MSFTNGP05.phx.gbl...
I'm trying a double indirect look-up table for some function pointer in my app (yep, I have good reason).
I'm trying to use std::map for the table but (because of the double indirection) I need to use a "std::map*"
Which I don't know how to map[index] (with a pointer)

Now perhaps I'm misusing it, I'm not sure (I know nothing of STL and I have some problem understanding its header)

Anyway here is my code (problem explained in red), if you could give me some tips.....
==============
static std::map<const char*, SELmap_sels;
static std::map<OClass, std::map<SEL, IMP>*map_imps;

void id::GetImpAlways(const char* name, SEL& sel, IMP& imp)
{
if( !_handle )
throw gcnew ObjectDisposedException(Class()->Name);

if(map_sels.find(name) == map_sels.end())
{
sel = sel_register_name(name);
map_sels[name] = sel;
}
else
{
sel = map_sels[name];
}

std::map<SEL, IMP* class_imps; // here I get the problematic "map *"
if(map_imps.find(_handle->class_pointer) == map_imps.end())
{
class_imps = new std::map<SEL, IMP>();
map_imps[_handle->class_pointer] = class_imps;
}
else
{
class_imps = map_imps[_handle->class_pointer];
}

if(class_imps->find(sel) == class_imps->end())
{
imp = get_imp(_handle->class_pointer, sel);
if( !imp )
throw gcnew ObjectiveCException("No such method");
class_imps[sel] = imp; // can't do that with 'map*', what should I so?
}
else
{
imp = class_imps[sel]; // can't do that with 'map*', what should I so?
}
}
==============

[Tom Widmer [VC++ MVP]]

Lloyd Dupont wrote:

I'm trying a double indirect look-up table for some function pointer in
my app (yep, I have good reason).
I'm trying to use std::map for the table but (because of the double
indirection) I need to use a "std::map*"
Which I don't know how to map[index] (with a pointer)

Now perhaps I'm misusing it, I'm not sure (I know nothing of STL and I
have some problem understanding its header)

Anyway here is my code (problem explained in red), if you could give me
some tips.....
==============

static std::map<const char*, SELmap_sels;

That's your first problem. That will base look up on pointer value, not
string value. Instead, you want:

#include <cstring>
struct CharStringLess
{
bool operator()(char const* lhs, char const* rhs) const
{
return std::strcmp(lhs, rhs) < 0;
}
};

static std::map<const char*, SEL, CharStringLessmap_sels;

[snip]

std::map<SEL, IMP* class_imps; // here I get the problematic "map *"

[snip]

class_imps[sel] = imp; // can't do that with 'map*', what
should I so?

You just need to dereference the pointer:
(*class_imps)[sel] = imp;
Or you could use a reference:
std::map<SEL, IMP>& class_imps_ref = *class_imps;
class_imps_ref[sel] = imp;

}
else
{
imp = class_imps[sel]; // can't do that with 'map*', what should
I so?

Same as above.

Tom

[Tom Widmer [VC++ MVP]]

Lloyd Dupont wrote:

never mind, I wil use my own C Hashtable...

This isn't a chatroom, it can take a while for anyone to read your post
(particularly if you post at the time you did, when neither Americans
nor Europeans tend to be working).

Tom

[Carl Daniel [VC++ MVP]]

Tom' already pointed out how to deal with your "map *" issue. From what
you've shown here, there's absolutely no need for you to store a pointer to
a map in the first place. Why complicate matters by storing a pointer to a
map? Also, when using the C++ standard library, liberal use of typedefs
will greatly increase the maintainability and understandability of your
code - not to mention saving you typing.

-cd

// uncompiled code - typos may be lurking

// borrowing from Tom's reply...
struct string_less_t
{
bool operator()(char const* lhs, char const* rhs) const
{
return std::strcmp(lhs, rhs) < 0;
}
};

typedef std::map<const char*, SEL, string_less_tsel_map_t;
typedef std::map<SEL, IMPimp_map_t;
typedef imp_map_t* imp_map_ptr_t;
typedef std::map<OClass, imp_map_tclass_map_t;

static sel_map_t map_sels;
static class_map_t map_imps;

void id::GetImpAlways(char char* name, SEL& sel, IMP& imp)
{
if( !_handle )
throw gcnew ObjectDisposedException(Class()->Name);

if(map_sels.count(name) == 0)
{
sel = sel_register_name(name);
map_sels[name] = sel;
}
else
{
sel = map_sels[name];
}

// not optimal - map_imps is searched twice, but the optimal
// code is very ugly and harder to understand

if(map_imps.count(_handle->class_pointer) == 0)
map_imps[_handle->class_pointer] = imp_map_t();

imp_map_ptr_t class_imps = &map_imps[_handle->class_pointer];

if(class_imps->count(sel) == 0)
{
imp = get_imp(_handle->class_pointer, sel);
if( !imp )
throw gcnew ObjectiveCException("No such method");
(*class_imps)[sel] = imp;
}
else
{
imp = (*class_imps)[sel];
}
}

[Lloyd Dupont]

???

"Tom Widmer [VC++ MVP]" <to********@hotmail.comwrote in message
news:ey**************@TK2MSFTNGP04.phx.gbl...

Lloyd Dupont wrote:

>never mind, I wil use my own C Hashtable...

This isn't a chatroom, it can take a while for anyone to read your post
(particularly if you post at the time you did, when neither Americans nor
Europeans tend to be working).

Tom

[Lloyd Dupont]

As I said, as you read, it was not necessary to take time to answer.
Anyway as you take the time I will politely reply ;-)

This is not a problem: I will fully compare pointer as these string are hard
coded constant and the lookup need to be as fast aspossible.
a pointer comparison is most appropriate.

Anyway it's all woking now with C Hashtable, whu should I bother?

"Tom Widmer [VC++ MVP]" <to********@hotmail.comwrote in message
news:ud*************@TK2MSFTNGP05.phx.gbl...

Lloyd Dupont wrote:

>I'm trying a double indirect look-up table for some function pointer in
my app (yep, I have good reason).
I'm trying to use std::map for the table but (because of the double
indirection) I need to use a "std::map*"
Which I don't know how to map[index] (with a pointer)
Now perhaps I'm misusing it, I'm not sure (I know nothing of STL and I
have some problem understanding its header)
Anyway here is my code (problem explained in red), if you could give me
some tips.....
==============

static std::map<const char*, SELmap_sels;

That's your first problem. That will base look up on pointer value, not
string value. Instead, you want:

#include <cstring>
struct CharStringLess
{
bool operator()(char const* lhs, char const* rhs) const
{
return std::strcmp(lhs, rhs) < 0;
}
};

static std::map<const char*, SEL, CharStringLessmap_sels;

[snip]

> std::map<SEL, IMP* class_imps; // here I get the problematic "map
*"

[snip]

> class_imps[sel] = imp; // can't do that with 'map*', what should
I so?

You just need to dereference the pointer:
(*class_imps)[sel] = imp;
Or you could use a reference:
std::map<SEL, IMP>& class_imps_ref = *class_imps;
class_imps_ref[sel] = imp;

> }
else
{
imp = class_imps[sel]; // can't do that with 'map*', what should
I so?

Same as above.

Tom

[Lloyd Dupont]

1st: forget about char* comparison, pointer comparison is most appropriate!

2nd: thanks for your sample anyway, it taught me some bits about STL I might
find handy in the future.

3rd: For the present, as I indicate in a previous post to save you the time
to answer, I already solved the problem with a C Hastable implementation I
wrote.

"Carl Daniel [VC++ MVP]" <cp*****************************@mvps.org.nospam >
wrote in message news:OY**************@TK2MSFTNGP03.phx.gbl...

Tom' already pointed out how to deal with your "map *" issue. From what
you've shown here, there's absolutely no need for you to store a pointer
to a map in the first place. Why complicate matters by storing a pointer
to a map? Also, when using the C++ standard library, liberal use of
typedefs will greatly increase the maintainability and understandability
of your code - not to mention saving you typing.

-cd

// uncompiled code - typos may be lurking

// borrowing from Tom's reply...
struct string_less_t
{
bool operator()(char const* lhs, char const* rhs) const
{
return std::strcmp(lhs, rhs) < 0;
}
};

typedef std::map<const char*, SEL, string_less_tsel_map_t;
typedef std::map<SEL, IMPimp_map_t;
typedef imp_map_t* imp_map_ptr_t;
typedef std::map<OClass, imp_map_tclass_map_t;

static sel_map_t map_sels;
static class_map_t map_imps;

void id::GetImpAlways(char char* name, SEL& sel, IMP& imp)
{
if( !_handle )
throw gcnew ObjectDisposedException(Class()->Name);

if(map_sels.count(name) == 0)
{
sel = sel_register_name(name);
map_sels[name] = sel;
}
else
{
sel = map_sels[name];
}

// not optimal - map_imps is searched twice, but the optimal
// code is very ugly and harder to understand

if(map_imps.count(_handle->class_pointer) == 0)
map_imps[_handle->class_pointer] = imp_map_t();

imp_map_ptr_t class_imps = &map_imps[_handle->class_pointer];

if(class_imps->count(sel) == 0)
{
imp = get_imp(_handle->class_pointer, sel);
if( !imp )
throw gcnew ObjectiveCException("No such method");
(*class_imps)[sel] = imp;
}
else
{
imp = (*class_imps)[sel];
}
}

[Hendrik Schober]

Lloyd Dupont <net.galador@ldwrote:

1st: forget about char* comparison, pointer comparison is most appropriate!

2nd: thanks for your sample anyway, it taught me some bits about STL I might
find handy in the future.

3rd: For the present, as I indicate in a previous post to save you the time
to answer, I already solved the problem with a C Hastable implementation I
wrote. ^

|
What an appropriate typo! Oh wait, you forgot an 'e'-+

<g>

[...]

Schobi

--
Sp******@gmx.de is never read
I'm Schobi at suespammers dot org

"The sarcasm is mightier than the sword."
Eric Jarvis

[Lloyd Dupont]

>3rd: For the present, as I indicate in a previous post to save you the

>time
to answer, I already solved the problem with a C Hastable implementation
I
wrote. ^

|
What an appropriate typo! Oh wait, you forgot an 'e'-+

?
I'm searching but I can't find....
Could you help me improve my english?

[Lloyd Dupont]

>3rd: For the present, as I indicate in a previous post to save you the

>time
to answer, I already solved the problem with a C Hastable implementation
I
wrote. ^

|
What an appropriate typo! Oh wait, you forgot an 'e'-+

I see... ASCII art, works better with notepad.
Yeah a 'h' was missing.

Anyway I still don't get your comment......

[Hendrik Schober]

Lloyd Dupont <net.galador@ldwrote:

3rd: For the present, as I indicate in a previous post to save you the
time
to answer, I already solved the problem with a C Hastable implementation
I
wrote. ^

|
What an appropriate typo! Oh wait, you forgot an 'e'-+

I see... ASCII art, works better with notepad.
Yeah a 'h' was missing.

Anyway I still don't get your comment......

You asked a question here and didn't give the world a
chance to read it, think about and answer you, but
/hasted/ to use some other implementation, despite
the fact that several people showed you what was
wrong with your code.

Schobi

--
Sp******@gmx.de is never read
I'm Schobi at suespammers dot org

"The sarcasm is mightier than the sword."
Eric Jarvis

[Lloyd Dupont]

You asked a question here and didn't give the world a

chance to read it, think about and answer you, but
/hasted/ to use some other implementation, despite
the fact that several people showed you what was
wrong with your code.

I had a problem, I asked a question first (always do like that).
Then I thought about it and after a couple of hours found an other way of
solving the problem which was:
1. more appropriate
2. I had no syntaxic problem to implement.

Then to save useless thinking for would-be helper I posted on the newsgroup:
"Solved"!

Now some people on the newsgroup start answering 3 hours after I say the
problem was solved.

Well, while it's nice to know how to solve my previous syntaxic problem and
improve my C++ syntax knowledge, it's a bit irrelevant now.

I'm surprised by the reaction here, looks like a bunch biggot to me...