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????

[Victor Bazarov]

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 ;

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

It is possible that you're encountering rounding (truncation in
case of integer division) and adding 1 doesn't do what you need
it to do.

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????

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?

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

[Simply_Red]

On 14 fév, 14:12, "Victor Bazarov" <v.Abaza...@com Acast.netwrote:

Simply_Redwrote :

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 ;

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.
?

>
It is possible that you're encountering rounding (truncation in
case of integer division) and adding 1 doesn't do what you need
it to do.

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????

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].

[red floyd]

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;
[redacted]

In addition to what Victor said to you, the definitions above are C-ish
and not really needed. They should be:

struct Limites {
double Debut;
double Fin;
};

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

No typedefs or "tag" names are necessary.

[Rolf Magnus]

Simply_Red wrote:

On 14 fév, 14:12, "Victor Bazarov" <v.Abaza...@com Acast.netwrote:

>Simply_Redwrot e:

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 ;

>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.

[Victor Bazarov]

Simply_Red wrote:

On 14 fév, 14:12, "Victor Bazarov" <v.Abaza...@com Acast.netwrote:

>Simply_Redwrot e:

>>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
mutlipostin g:

>>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;
}ElemTabCon t;

>>void myfunc( )
{
.....
ElemTabCont * 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.

You have stumbled upon a well-known (now to you as well) situation
when 16/0.1 is not 160 (exactly) but rather 159.99999999999 9. Add
1 to it and you get 160.99999999999 9 and assign it to a 'long', you
get 160. It's called "imprecise representation of a decimal value"
and essentially all computers with binary FP units suffer from it.

To calculate those things "correctly" , add 1.0000001 instead of 1:

long nbNiveau = (yhi-ylo)/stepY + 1.0000001;

It's not pretty, but it will work better. The number of zeros after
the decimal point depends on your 'yhi-ylo' scale.

?

>>
It is possible that you're encountering rounding (truncation in
case of integer division) and adding 1 doesn't do what you need
it to do.

>>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??? ?

>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?)

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

[Simply_Red]

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_Redwrote :
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 ;

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.....

[Victor Bazarov]

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_Redwr ote:
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
mutlipostin g:

>>>>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;
}ElemTabCon t;

>>>>void myfunc( )
{
.....
ElemTabCo nt * 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
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

[Kai-Uwe Bux]

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

[Simply_Red]

On 14 fév, 14:35, "Victor Bazarov" <v.Abaza...@com Acast.netwrote:

Simply_Red wrote:

On 14 fév, 14:12, "Victor Bazarov" <v.Abaza...@com Acast.netwrote:

Simply_Redwrote :
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 ;

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.

You have stumbled upon a well-known (now to you as well) situation
when 16/0.1 is not 160 (exactly) but rather 159.99999999999 9. Add
1 to it and you get 160.99999999999 9 and assign it to a 'long', you
get 160. It's called "imprecise representation of a decimal value"
and essentially all computers with binary FP units suffer from it.

To calculate those things "correctly" , add 1.0000001 instead of 1:

long nbNiveau = (yhi-ylo)/stepY + 1.0000001;

It's not pretty, but it will work better. The number of zeros after
the decimal point depends on your 'yhi-ylo' scale.

?

It is possible that you're encountering rounding (truncation in
case of integer division) and adding 1 doesn't do what you need
it to do.

>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????

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?)

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

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