Problem regarding C++ STL

[vermarajeev]

Hi guys,
I'm working on a project where I need to remove Qt libraries and use C++ STL.
I need to replace QPtrList::findRef defined in Qt with C++ STL alternative . But unable to get any solution.

For example
I have used STL's find(InputIterator first, InputIterator last, const T& value) to replace QPtrList::find. The code can be seen as below

Defined in Qt3

if( -1 == steps.find( s ) )

if( -1 == steps.find( s ) )

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Alternative in C++ STL

StepListIterator sIt = find( steps.begin(), steps.end(), s);
if (sIt == steps.end())
 { 
    //not found perform relevant operation
 }

StepListIterator sIt = find( steps.begin(), steps.end(), s);
if (sIt == steps.end())
 { 
    //not found perform relevant operation
 }

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Similar way I need to replace Qt's QPtrList::findRef with an C++ STL alternative.
Please help me

Waiting for your reply

Thankx in advance

[vermarajeev]

Hi guys,
I'm working on a project where I need to remove Qt libraries and use C++ STL.
I need to replace QPtrList::findRef defined in Qt with C++ STL alternative . But unable to get any solution.

For example
I have used STL's find(InputIterator first, InputIterator last, const T& value) to replace QPtrList::find. The code can be seen as below

Defined in Qt3
Qt Code:

if( -1 == steps.find( s ) )

if( -1 == steps.find( s ) )

To copy to clipboard, switch view to plain text mode 

Alternative STL Code:

StepListIterator sIt = find( steps.begin(), steps.end(), s);
if (sIt == steps.end()) 
{
     //not found perform relevant operation 
}

StepListIterator sIt = find( steps.begin(), steps.end(), s);
if (sIt == steps.end()) 
{
     //not found perform relevant operation 
}

To copy to clipboard, switch view to plain text mode 

Similar way I need to replace Qt's QPtrList::findRef with an C++ STL alternative.
Please help me
This is really improtant to me

Waiting for your reply

Thankx in advance

[wysota]

What is "s"? If "s" is a pointer, then the implementation you provided is the implementation of findRef and not Find.

[vermarajeev]

Hi, thankx for your reply

Here are the declarations given
in Qt

typedef QList<SynStep> SynStepList;
typedef QListIterator<SynStep>	StepListIterator;
SynStep* s; //where SynStep is a class defined by me
class StepList : public SynStepList
    {
 
    };
StepList steps;
if( -1 == steps.find( s ) )

typedef QList<SynStep> SynStepList;
typedef QListIterator<SynStep>	StepListIterator;
SynStep* s; //where SynStep is a class defined by me
class StepList : public SynStepList
    {

    };
StepList steps;
if( -1 == steps.find( s ) )

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in STL

typedef std::vector<SynStep*>  SynStepList;
typedef std::vector<SynStep*>::iterator  StepListIterator;
SynStep* s; //where SynStep is a class defined by me
 
class StepList : public SynStepList
    {
 
    };
StepList steps;
StepListIterator sIt = find( steps.begin(), steps.end(), s);
if (sIt == steps.end()) 
{     
//not found perform relevant operation 
}

typedef std::vector<SynStep*>  SynStepList;
typedef std::vector<SynStep*>::iterator  StepListIterator;
SynStep* s; //where SynStep is a class defined by me

class StepList : public SynStepList
    {

    };
StepList steps;
StepListIterator sIt = find( steps.begin(), steps.end(), s);
if (sIt == steps.end()) 
{     
//not found perform relevant operation 
}

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Ok if that is the implementation for FindRef than can you please tell me how can I
implement Find....

[wysota]

But these declarations are from Qt4 and in the first post you gave Qt3 code.

QPtrList::find compares items referenced by pointers, findRef compares pointers directly, therefore if you want to compare items, you have to convince STL to compare items. I doubt it is directly possible so you'll probably have to subclass or at least create a custom compare functor and tell find() to use it.

[jacek]

There is no difference between find() and findRef() if you have a vector of pointers.

[jacek]

Threads merged.

Please don't ask the same question in different section.

[bood]

There is no difference between find() and findRef() if you have a vector of pointers.

Of course there is.
Diffrenent pointers can point to different objects that have same value.

[jacek]

Of course there is.
Diffrenent pointers can point to different objects that have same value.

But still, if the value is a pointer, there is no difference, since find() doesn't dereference pointers.

[wysota]

But still, if the value is a pointer, there is no difference, since find() doesn't dereference pointers.

I guess that for Qt3 with QPtrList it might make a difference. Of course STL doesn't support dedicated lists for pointers, so to port the same behaviour to STL, one has to provide a custom compare functor.

[vermarajeev]

I guess that for Qt3 with QPtrList it might make a difference. Of course STL doesn't support dedicated lists for pointers, so to port the same behaviour to STL, one has to provide a custom compare functor.

Can you please visualize with an example??