Fake Expected a declaration

[Jan Sheva]

Hello. There is some test to make a function that return a pointer to matrix array
Program bullding is succesful and it work succesful. A result in QTextEdit looks like this:
1,2,3,4,5,6,7,8,
9,10,11,12,13,14,15,16,
17,18,19,20,21,22,23,24,
25,26,27,28,29,30,31,32,

But QT Creator say "Expected a declaration" (see screen http://imageshack.com/a/img673/9086/WodPUb.jpg)
My questions:

1. What a reason of that QT Creator say " Expected a declaration" and can not find the declaration in this function: BYTE (*MyProg::GetProgressiveMatrix(int n))[8] ?
2. Is there some other way to return a pointer to matrix array BYTE WPlanMap[4][8];

Code:
//----------------------------------------------Header.h
#ifndef Test_H
#define Test_H
#include "ui_USEROK.h"
#include <QtGui>
#include <QtCore>
class MyProg : public QWidget, public Ui::MyProg
{
Q_OBJECT
public:
MyProg(QWidget* pwgt = 0, Qt::WindowFlags f = 0);
BYTE (*GetProgressiveMatrix(int n))[8];
public slots:
void Deal3Start();
protected:
BYTE WPlanMap[4][8];
};
#endif

//---------------------------------Source.h

#include "Header.h"
#include <cmath>
#include <cstdlib>
#include <cstdio>
MyProg::MyProg(QWidget* pwgt,Qt::WindowFlags f) : QWidget(pwgt,f){
setupUi(this);
setFixedSize(700, 600);
connect(Deal3Button, SIGNAL(clicked()), this, SLOT(Deal3Start()));
}
void MyProg::Deal3Start(){
QString ResultStr = "";
QString TempStr;
BYTE (*pWPlanMap)[8];
pWPlanMap = GetProgressiveMatrix(TestBox->value());

for (int i = 0; i < 4; ++i){
    for (int j = 0; j < 8; ++j){
        ResultStr = ResultStr + TempStr.setNum(pWPlanMap[i][j]) + ",";
    }
    ResultStr = ResultStr + '\n';
}
TestResult->setText(ResultStr); //Result string

}
BYTE (MyProg::GetProgressiveMatrix(int n))[8] //Expected a declaration ???(see screen http://imageshack.com/a/img673/9086/WodPUb.jpg)
{
for (int i = 0; i < 4; ++i){
for (int j = 0; j < 8; ++j){
WPlanMap[i][j] = n+j+(i8);
}
}
return WPlanMap;
}

[SGaist]

Hi and welcome to devnet,

BYTE (*GetProgressiveMatrix(int n))[8]; is not a declaration. It's a something of a mix between a function and an array declaration.

You can return a BYTE ** from your function. Depending on what you actually need that matrix for, Qt provides QGenericMatrix that you can use.

[Jan Sheva]

Thanks. It is interesting.
For example I have matrix
int Map[2][4] = {......};

How to create a pointer to Map and return it. Can you code declaration of such function and create a pointer to Map that returned?
and then print Map in loop

[mrjj]

returning multi-dim arrays from functions has ugly syntax.
please see
http://stackoverflow.com/questions/3716595/c-returning-multidimension-array-from-function

something like

#include <QDebug>

const int MaxDim = 5;
typedef int ( *myarray_return ) [MaxDim];
myarray_return get_array()
{
    static int local_myarray[MaxDim][MaxDim];
    for ( int i = 0; i < MaxDim; i ++ )
        for ( int h = 0; h < MaxDim; h++ )
        { local_myarray[i][h] = i * 10; }

    return local_myarray;

}

int main ( int argc, char* argv[] )
{
   myarray_return ref_array = get_array();
    for ( int i = 0; i < MaxDim; i ++ )
        for ( int h = 0; h < MaxDim; h++ )
        { qDebug() << ref_array[i][h]; }

}

ps. sorry for no code formatting. Seems not be included in the editor anymore.

[edit: Added missing coding tags: ``` before and after the code SGaist]

[Huulivoide]

int **matrix;
is a 2 dimensional matrix, pointer of pointers, or dynamically allocated array
of pointers (dynamically allocated arrays).

Init like:

int width 5;
int height = 5;

int **matrix = new int*[height];
for (int row = 0; row < height; ++row)
{
    matrix[row] = new int[width];
}

[SGaist]

There's a summary of the markdown tags used by the forum on the bottom of the page

[mrjj]

This post is deleted!

[mrjj]

@SGaist ahh thanks. I keep forgetting. When editor open, its not visible unless you scroll :)