Help please, strange behavior

[Simply_Red]

i'm sorry i posted this in other groupes, and i didn't see it, and as
this group is most actif, i repost it here, and sorry for
mutliposting:

Hi,
i'm using VC6, i have this declaration:

typedef struct tagTLimite {
double Debut;
double Fin;
}Limites;

typedef struct TagElemTab {
double NivY;
bool Existe;
std::vector<Lim itesPtLimites;
}ElemTabCont;

void myfunc( )
{
......
ElemTabCont * ContNonOrd;//contour non ordone
long nbNiveau = (yhi-ylo)/stepY +1 ;
ContNonOrd = new ElemTabCont [nbNiveau];
......
}
i don't know why,nbNiveau is equal to (yhi-ylo)/stepY, it didn't
+1????and even if i put:
ContNonOrd = new ElemTabCont [nbNiveau+1]; the size of ContNonOrd =
nbNiveau????

[Simply_Red]

On 14 fév, 14:37, "Victor Bazarov" <v.Abaza...@com Acast.netwrote:

Simply_Red wrote:

On 14 fév, 14:29, Rolf Magnus <[e-mail]:

Simply_Red wrote:
On 14 fév, 14:12, "Victor Bazarov" <v.Abaza...@com Acast.netwrote:
Simply_Redwro te:
i'm sorry i posted this in other groupes, and i didn't see it,
and as this group is most actif, i repost it here, and sorry for
mutliposting :

>>>Hi,
i'm using VC6, i have this declaration:

>>>typedef struct tagTLimite {
double Debut;
double Fin;
}Limites;

>>>typedef struct TagElemTab {
double NivY;
bool Existe;
std::vector<Lim itesPtLimites;
}ElemTabCont ;

>>>void myfunc( )
{
.....
ElemTabCon t * ContNonOrd;//contour non ordone
long nbNiveau = (yhi-ylo)/stepY +1 ;

>>What is the type of 'yhi', 'ylo', 'stepY'? What are their values?
What value do you get in 'nbNiveau'? What did you expect

>yhi, ylo, stepY are doubles values: 16, 0, 0.1 respectively
I get 160 in nbNiveau, and I need 161.

double isn't precise either. Note that 0.1 in binary is a periodic
number that cannot be represented exactly. So instead of 0.1, you
get the closest representable value. As a result, you might get
something like 160.99999999998 , which gets truncated to 160 when
converted to long.

but if 160.999999998 is truncated to 160, 159.99999998 must be
truncated to 159.....

Yes... And?

V
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Please remove capital 'A's when replying by e-mail
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when i just put long nbNiveau = (yhi-ylo)/stepY. i get nbNiveau = 160
not 159

[Simply_Red]

On 14 fév, 14:35, Kai-Uwe Bux <jkherci...@gmx .netwrote:

Simply_Red wrote:

i'm sorry i posted this in other groupes, and i didn't see it, and as
this group is most actif, i repost it here, and sorry for
mutliposting:

Hi,
i'm using VC6, i have this declaration:

typedef struct tagTLimite {
double Debut;
double Fin;
}Limites;

typedef struct TagElemTab {
double NivY;
bool Existe;
std::vector<Lim itesPtLimites;
}ElemTabCont;

void myfunc( )
{
.....
ElemTabCont * ContNonOrd;//contour non ordone
long nbNiveau = (yhi-ylo)/stepY +1 ;
ContNonOrd = new ElemTabCont [nbNiveau];
.....
}
i don't know why,nbNiveau is equal to (yhi-ylo)/stepY, it didn't
+1????and even if i put:

How did you tell? Probably you misinterpret some output that we do not see
because your code snippet is incomplete.

and even if i put: ContNonOrd = new ElemTabCont [nbNiveau+1]; the size of
ContNonOrd = nbNiveau????

Again, how did you tell?

Please post a minimal complete program that shows the problem. With the code
fragments from above, there is no way to tell what the problem is
(especially since we do not even know the types of yhi, yhl, and stepY.

Best

Kai-Uwe Bux

bool __declspec(dlle xport) CALLBACK NewMakeContour( LPSAFEARRAY FAR
*saY, VARIANT FAR *pvArray, double yhi, double ylo,double stepX,double
stepY)
{

SAFEARRAYBOUND sabound[1]; // 1-D array
SAFEARRAY FAR* psa = NULL; // SAFEARRAY structure pointer
HRESULT hr; // Operations result
float HUGEP *vbY; // Tableau Contenant tous les points
long UboundY;
double V;
long ptTabRes,ptTabS ource;

hr = SafeArrayAccess Data(*saY, (void HUGEP**)&vbY);
UboundY = (*saY)->rgsabound[0].cElements;

ElemTabCont * ContNonOrd;//contour non ordone
long nbNiveau = (yhi-ylo)/stepY+1 ;// +1 ; je ne sais pas pourquoi il
ne me fait pas le + 1;
ContNonOrd = new ElemTabCont[nbNiveau];
//ContNonOrd = new ElemTabCont[161];//donc je suis obliger de le
faire ici

V = vbY[1];//le premier pt est un pt du contour
ptTabRes = 0;
ptTabSource = 0;
while (FRound(V,3) <= FRound(yhi,3))
{
FindLevelPt(vbY , ptTabSource,Con tNonOrd,ptTabRe s,V,UboundY,ste pX);
ptTabRes++;
V+=stepY;
}
delete[] ContNonOrd;
hr = SafeArrayUnacce ssData(*saY);
return true
}
void FindLevelPt(flo at* TabSource, long& ptTabSource,Ele mTabCont*
ContNonOrd,long ptTabRes,double V, long UBoundY, float StepX) {

Limites XLimites;

ContNonOrd[ptTabRes].NivY = V;
//si on est au niv superieur a V=>pas de point au niveau V
if (FRound(TabSour ce[ptTabSource+1],3) == FRound(V,3))
{
ContNonOrd[ptTabRes].Existe = true;

bool nivDepasse = false;
bool terminer = false;
while (!nivDepasse && !terminer)
{
XLimites.Debut = TabSource[ptTabSource];

bool trouve = false;//true si on trouve la limite du segment
ptTabSource+=3;//le debut a ete deja trouver
while(!trouve && ptTabSource <= UBoundY-3) //-1 z, -2 y -3 x
{
nivDepasse = (FRound(TabSour ce[ptTabSource+1],3) FRound(V,3));
trouve = (FRound(TabSour ce[ptTabSource]-TabSource[ptTabSource-3],
3)>FRound(StepX ,3)) || nivDepasse ;
ptTabSource+=3;
}
if (trouve) {
XLimites.Fin = TabSource[ptTabSource-6];
ptTabSource-=3;//pour pointer au prochain debut.
ContNonOrd[ptTabRes].PtLimites.push _back(XLimites) ;
}
else {//le dernier pt ou la derniere ligne
terminer = true;
XLimites.Fin = TabSource[ptTabSource-3];
ContNonOrd[ptTabRes].PtLimites.push _back(XLimites) ;
}
}
}
else ContNonOrd[ptTabRes].Existe = false;
}

[Rolf Magnus]

Simply_Red wrote:

>That last statement is beyond me. What do you mean by "the size of
ContNotOrd"? How the hell can you know the size? How can it be
different from the size you requested?

i just verify in watch window ContNotOrd[160].

I don't know how you do that, but tell me, if you do

int main() {
long nbNiveau = 160;
char *ContNotOrd = new char[nbNiveau + 1];
}

and "verify in watch window", do you get 160 or 161 _elements_? Do
not tell me the last index (it is less by 1 than the size, right?)

when i give a value to ContNotOrd[161] i have a crash,

That's not surprising. If nbNiveau is 160, then you allocate an array with
161 elements, numbered 0 to 160. So if you try to access the element with
index 161, you are going past the end of your array.

and 160 no.....for my example i check the vector of the 160 elem, when
there is no pb it contain _First = 0 _Last = 0 _End = 0.

[Simply_Red]

when i just put long nbNiveau = (yhi-ylo)/stepY. i get nbNiveau = 160

not 159

i was wrong it's 159...........

and if i use float, is there pbs with the precision???

[Simply_Red]

On 14 fév, 15:25, Rolf Magnus <[e-mail]:

>
That's not surprising. If nbNiveau is 160, then you allocate an array with
161 elements, numbered 0 to 160. So if you try to access the element with
index 161, you are going past the end of your array.

i know this, but my pb is that i need that nbNiveau = 161, and i get
160, i was sure that when the value is betwwen 160.51 and
160.99999999, in long the compilator will replace it with 160

[Simply_Red]

On 14 fév, 15:33, "Simply_Red " <Simply.Re...@g mail.comwrote:

On 14 fév, 15:25, Rolf Magnus <[e-mail]:

That's not surprising. If nbNiveau is 160, then you allocate an array with
161 elements, numbered 0 to 160. So if you try to access the element with
index 161, you are going past the end of your array.

i know this, but my pb is that i need that nbNiveau = 161, and i get
160, i was sure that when the value is betwwen 160.51 and
160.99999999, in long the compilator will replace it with 160

i wanted to say: i was sure that when the value is betwwen 160.51 and

160.99999999, in long the compilator will replace it with 161

[Victor Bazarov]

Simply_Red wrote:

[..]
i wanted to say: i was sure that when the value is betwwen 160.51 and

>160.99999999 , in long the compilator will replace it with 161

What in the world made you so *sure* of that? Just curious...

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

[Victor Bazarov]

Simply_Red wrote:

>when i just put long nbNiveau = (yhi-ylo)/stepY. i get nbNiveau =
160 not 159

i was wrong it's 159...........

and if i use float, is there pbs with the precision???

Of course. Just like if you use 'double', only worse.

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

[Rolf Magnus]

Simply_Red wrote:

On 14 fév, 15:33, "Simply_Red " <Simply.Re...@g mail.comwrote:

>On 14 fév, 15:25, Rolf Magnus <[e-mail]:

That's not surprising. If nbNiveau is 160, then you allocate an array
with 161 elements, numbered 0 to 160. So if you try to access the
element with index 161, you are going past the end of your array.

i know this, but my pb is that i need that nbNiveau = 161, and i get
160, i was sure that when the value is betwwen 160.51 and
160.99999999 , in long the compilator will replace it with 160

i wanted to say: i was sure that when the value is betwwen 160.51 and

>160.99999999 , in long the compilator will replace it with 161

Well, that's not the case. In C++, when converting a floating point value
into an integer, the fractional part is always truncated.

[Simply_Red]

On 14 fév, 15:41, "Victor Bazarov" <v.Abaza...@com Acast.netwrote:

Simply_Red wrote:

[..]
i wanted to say: i was sure that when the value is betwwen 160.51 and

160.99999999, in long the compilator will replace it with 161

What in the world made you so *sure* of that? Just curious...

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

in vb it's like that, i know that doesn't meen that C++ must do the
same :-(