help me

gentleguy

dear all any problem occurred when the following errers happened? : error C2057: expected constant expression thanks

Li Zhiyuan 5/10/2006

Cedric Moonen · Li Zhiyuan 5/10/2006

Well, the error message is clear enough no ? It says that somewhere the compiler expects a constant variable but you didn't provide it. And without any piece of code, it is impossible to tell more.

Cédric Moonen Software developer
Charting control [v1.2]

kingori · Li Zhiyuan 5/10/2006

hi; most likely you have declared an array without indicating its size e.g long m_lStudents[]; if thats the case then give it size;

Hamid Taebi · Li Zhiyuan 5/10/2006

Is this question related to your previous question?

gentleguy

no, this is what i just studied for dynamic multiple array...the code is here.... nt n,m; double c[n][m] = NULL; double * a[] = NULL; double * b[] = NULL; cin >> n; cin>>m; b[] = new double[m]; a[] = new double[n]; for (int i=0; i>>n; i++) { a[i] =(double) rand()/RAND_MAX; } for (int j=0; j{ a[j] =(double) rand()/RAND_MAX; } for (int k=0;k for (int kk=0;kk { if (k==0) c[k][kk] = a[k]; else c[k][kk] = b[kk]; } cout <<"\n"; delete [] a; a = NULL; } this is what i created a 2 D dynamic array...but the problem is there...how to create a 2D dynamic array? thanks

Li Zhiyuan 5/10/2006

Iain Clarke Warrior Programmer · Li Zhiyuan 5/10/2006

li zhiyuan wrote:

how to create a 2D dynamic array?

Simple answer... You can't. Which is why you're getting an error. Longer answer... You cheat. Create a one dimensional dynamic array. But make it an array of double *s, then create those arrays.

typedef double *pdouble;

// create a 2D virtual array
pdouble *c = new pdouble [N];
for (n = 0; n < N; n++)
c [n] = new double [m];

.... ; do your processing code

// Tidy up 2D virtual array
for (n = 0; n < N; n++)
delete [] c [n];
delete [] c;

Notice I'm using delete [] instead of delete. The [] means it will call the destructor for each member of the array(s). For simple types like double and double *, it makes no difference. But it makes no harm, and is a good habit to get into. Then you can make arrays of classes/structs that *could* have destructors, and you'll be thankful for your good habits. I hope that helped, Iain. ps, In addition, please use the <pre> / </pre> keywords in your posts. And longer variables. They're hard to read now, and you're going to hate yourself in two years time.

gentleguy

thanks a lot friend, could you provide me with complete code creating 2 D dynamic array? thanks again

Li Zhiyuan

Iain Clarke Warrior Programmer

I already did provide you with complete code for creating a 2d array, and then destroying it. Look at the post you replied to.

David Crow

Please remove your blinders. :rolleyes:

"Normal is getting dressed in clothes that you buy for work and driving through traffic in a car that you are still paying for, in order to get to the job you need to pay for the clothes and the car and the house you leave vacant all day so you can afford to live in it." - Ellen Goodman

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