little problem with find stl's algorithm

  • Thread starter Thread starter Jacobo Rodriguez Villar
  • Start date Start date
J

Jacobo Rodriguez Villar

Hello,

I'm trying to use the find algo from the stl library, over a list of
pointers:

std::list<Program *> m_programs

in this method:
Program *GLSLManager::GetProgram(GLhandleARB id)
{
std::list<Program *>::iterator result;
result = find(m_programs.begin(), m_programs.end(), id);
if(result!=m_programs.end())
return *result;
else
return NULL;
}

As far I know I must implement the operator== between the types
GLhandleARB (it is a typedef of ints) and Program * pointers. I do this
by this way:

int operator==(Program *program, GLhandleARB id); /*it is not a member
of Program class*/

[implementation]
int operator==(Program *program, GLhandleARB id)
{
return program->GetHandle() == id;
}

but I'm having errors with this:
error C2803: 'operator == must have at least a formal parameter of class
type'

Anyone can help me?

thanks in advance


--
Jacobo Rodríguez Villar

TyphoonLabs Lead Programmer

http://www.typhoonlabs.com
 
I'm trying to use the find algo from the stl library, over a list of
pointers:

std::list<Program *> m_programs

in this method:
Program *GLSLManager::GetProgram(GLhandleARB id)
{
std::list<Program *>::iterator result;
result = find(m_programs.begin(), m_programs.end(), id);
if(result!=m_programs.end())
return *result;
else
return NULL;
}

As far I know I must implement the operator== between the types
GLhandleARB (it is a typedef of ints) and Program * pointers. I do this
by this way:

int operator==(Program *program, GLhandleARB id); /*it is not a member
of Program class*/

[implementation]
int operator==(Program *program, GLhandleARB id)
{
return program->GetHandle() == id;
}

but I'm having errors with this:
error C2803: 'operator == must have at least a formal parameter of class
type'

Anyone can help me?

thanks in advance
Click to expand...

Your GLhandleARB is probably typedef of some primitive type or pointer. If
you could declare GLhandleARB as a struct, class, or enum you would
succeeded in operator== overloading.
 
Jacobo said:
Hello,

I'm trying to use the find algo from the stl library, over a list of
pointers:

std::list<Program *> m_programs

in this method:
Program *GLSLManager::GetProgram(GLhandleARB id)
{
std::list<Program *>::iterator result;
result = find(m_programs.begin(), m_programs.end(), id);
if(result!=m_programs.end())
return *result;
else
return NULL;
}

As far I know I must implement the operator== between the types
GLhandleARB (it is a typedef of ints) and Program * pointers. I do this
by this way:

int operator==(Program *program, GLhandleARB id); /*it is not a member
of Program class*/

[implementation]
int operator==(Program *program, GLhandleARB id)
{
return program->GetHandle() == id;
}

but I'm having errors with this:
error C2803: 'operator == must have at least a formal parameter of class
type'

Anyone can help me?
Click to expand...

You can't overload operators for primitive types (I assume GLhandleARG
is just a typedef for a primitive type). Instead, you should use a
functor and find_if. e.g.

struct ProgramHandleChecker
{
GLhandleARB id;
ProgramHandleChecker(GLhandleARB id):id(id){}
bool operator()(Program* p) const
{
return p != 0 && id == p->GetHandle();
}
};

//...
result = find_if(m_programs.begin(), m_programs.end(),
ProgramHandleChecker(id));

If you use boost::bind (soon to be semi-standard as std::tr1::bind), you
can do:

result = find_if(m_programs.begin(), m_programs.end(),
bind<bool>(std::equals<GLhandleARB>(), bind(&Program::GetHandle, _1), id));

which saves the extra functor, but is more complex.

Tom
 
Yes, GLhandleARB is a typedef of int, I'll try use it into a struct,
many thanks.
Jacobo said:
Hello,

I'm trying to use the find algo from the stl library, over a list of
pointers:

std::list<Program *> m_programs

in this method:
Program *GLSLManager::GetProgram(GLhandleARB id)
{
std::list<Program *>::iterator result;
result = find(m_programs.begin(), m_programs.end(), id);
if(result!=m_programs.end())
return *result;
else
return NULL;
}

As far I know I must implement the operator== between the types
GLhandleARB (it is a typedef of ints) and Program * pointers. I do
this by this way:

int operator==(Program *program, GLhandleARB id); /*it is not a
member of Program class*/

[implementation]
int operator==(Program *program, GLhandleARB id)
{
return program->GetHandle() == id;
}

but I'm having errors with this:
error C2803: 'operator == must have at least a formal parameter of
class type'

Anyone can help me?
Click to expand...


You can't overload operators for primitive types (I assume GLhandleARG
is just a typedef for a primitive type). Instead, you should use a
functor and find_if. e.g.

struct ProgramHandleChecker
{
GLhandleARB id;
ProgramHandleChecker(GLhandleARB id):id(id){}
bool operator()(Program* p) const
{
return p != 0 && id == p->GetHandle();
}
};

//...
result = find_if(m_programs.begin(), m_programs.end(),
ProgramHandleChecker(id));

If you use boost::bind (soon to be semi-standard as std::tr1::bind), you
can do:

result = find_if(m_programs.begin(), m_programs.end(),
bind<bool>(std::equals<GLhandleARB>(), bind(&Program::GetHandle, _1), id));

which saves the extra functor, but is more complex.

Tom
Click to expand...


--
Jacobo Rodríguez Villar

TyphoonLabs Lead Programmer

http://www.typhoonlabs.com
 
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