Creating array of data types

[Madhur]

Hi All,

I would like you help me in creating an array of data types.

I am interested in look at the the data type which looks like this
Array a[10]={int,float,cha r,int*......... ............... ......},

so that a[0] should return me int and a[1] should return me
float..which helps me in runtime type casting.

I do not know how to create such an array. If i create so what would
be the data type of "Array".
This is basically a variable to "data type" conversion.

Or is there any better way to do this.

Looking keenly for the response..

Regards,
Madhur

[Mark Bluemel]

Madhur wrote:

Hi All,

I would like you help me in creating an array of data types.

I don't think I can do that...

I am interested in look at the the data type which looks like this
Array a[10]={int,float,cha r,int*......... ............... ......},

What the **** does that mean?

so that a[0] should return me int and a[1] should return me
float..which helps me in runtime type casting.

You could possibly do something with unions, but the idea of arrays is
that elements are essentially equivalent. If you know that a[0] is an
int, a[1] a float, etc then they should simply be individual variables,
I'd have thought.

>
I do not know how to create such an array. If i create so what would
be the data type of "Array".
This is basically a variable to "data type" conversion.

Or is there any better way to do this.

I think you should tell us what you are trying to achieve in broader
terms - your original requirement - rather than telling us how you are
trying to do it.

[Richard Heathfield]

Mark Bluemel said:

<snip>

What the **** does that mean?

In a declaration context, it means that does is a pointer to pointer to
pointer to pointer to an object of type the.

In an expression context, it could mean that the is to be multiplied by
the value pointed to by the value pointed to by the value pointed to by
does, or it could simply mean the value pointed to by the value pointed
to by the value pointed to by the value pointed to by does.

This article was brought to you by courtesy of the Coincidentally Right
Justified Usenet Articles Association. Happily, the coincidence extends
even to the very paragraph that describes it.

--
Richard Heathfield <http://www.cpax.org.uk >
Email: -www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999

[Madhur]

Thanks for the info...

Array as referred above is list hundreds of user defined data types
and it is impossible for me to take care of it each time unless i have
an explicit hash maintained to it which i can not entertain right
now.. therefore I was looking for array of data types..which seems to
be impossible...

Yes Enumeration is the only way to go..but is there any how i can link
an index to the enum data type...say enum looks like this

typedef union enum1
{
type0,
type1,
type2,
type3
..
..
..
type n
}ENUM1;

so if get an index say 2 can i extract type2 without using type2
explicity..
in better way..is there somehow ican mention ENUM(2) and which should
get me type2????


On Jul 24, 1:34 pm, Mark Bluemel <mark_blue...@p obox.comwrote:

Madhur wrote:

Hi All,

I would like you help me in creating an array of data types.

I don't think I can do that...

I am interested in look at the the data type which looks like this

Array a[10]={int,float,cha r,int*......... ............... ......},

What the **** does that mean?

so that a[0] should return me int and a[1] should return me
float..which helps me in runtime type casting.

You could possibly do something with unions, but the idea of arrays is
that elements are essentially equivalent. If you know that a[0] is an
int, a[1] a float, etc then they should simply be individual variables,
I'd have thought.

I do not know how to create such an array. If i create so what would
be the data type of "Array".
This is basically a variable to "data type" conversion.

Or is there any better way to do this.

I think you should tell us what you are trying to achieve in broader
terms - your original requirement - rather than telling us how you are
trying to do it.

[Mark Bluemel]

Madhur wrote:

Thanks for the info...

Please don't top post.

>
On Jul 24, 1:34 pm, Mark Bluemel <mark_blue...@p obox.comwrote:

>>I think you should tell us what you are trying to achieve in broader
terms - your original requirement - rather than telling us how you are
trying to do it.

Array as referred above is list hundreds of user defined data types
and it is impossible for me to take care of it each time unless i have
an explicit hash maintained to it which i can not entertain right
now.. therefore I was looking for array of data types..which seems to
be impossible...

Yes Enumeration is the only way to go..but is there any how i can link
an index to the enum data type...say enum looks like this

typedef union enum1
{
type0,
type1,
type2,
type3
.
.
.
type n
}ENUM1;

so if get an index say 2 can i extract type2 without using type2
explicity..
in better way..is there somehow ican mention ENUM(2) and which should
get me type2????

I think you need an enumeration of types:-

enum TYPE {
INT,
LONG,
FLOAT,
DOUBLE,
...
};

A union of data values :-
union values {
int ival;
long lval;
float fval;
double dval;
..
};

And an array of structures :-

struct data_item {
enum TYPE type;
union values value;
};

struct data_item my_data[100];

Then you can use a switch to get the data for a particular data_item.
You could even have a really ugly macro -

#define ENUM(n) (my_data[n].type == INT)?my_data[n].value.ival: \
(my_data[n].type == LONG)?my_data[n].value.lval: \
...

Untested code etc...

[Madhur]

On Jul 24, 2:24 pm, Mark Bluemel <mark_blue...@p obox.comwrote:

Madhur wrote:

Thanks for the info...

Please don't top post.

On Jul 24, 1:34 pm, Mark Bluemel <mark_blue...@p obox.comwrote:

>I think you should tell us what you are trying to achieve in broader
terms - your original requirement - rather than telling us how you are
trying to do it.

Array as referred above is list hundreds of user defined data types
and it is impossible for me to take care of it each time unless i have
an explicit hash maintained to it which i can not entertain right
now.. therefore I was looking for array of data types..which seems to
be impossible...

Yes Enumeration is the only way to go..but is there any how i can link
an index to the enum data type...say enum looks like this

typedef union enum1
{
type0,
type1,
type2,
type3
.
.
.
type n
}ENUM1;

so if get an index say 2 can i extract type2 without using type2
explicity..
in better way..is there somehow ican mention ENUM(2) and which should
get me type2????

I think you need an enumeration of types:-

enum TYPE {
INT,
LONG,
FLOAT,
DOUBLE,
...

};

A union of data values :-
union values {
int ival;
long lval;
float fval;
double dval;
..

};

And an array of structures :-

struct data_item {
enum TYPE type;
union values value;

};

struct data_item my_data[100];

Then you can use a switch to get the data for a particular data_item.
You could even have a really ugly macro -

#define ENUM(n) (my_data[n].type == INT)?my_data[n].value.ival: \
(my_data[n].type == LONG)?my_data[n].value.lval: \
...

Untested code etc...

But what is the data type of the variable which stores the result thus
returned...
which brings again back to the question...

[Mark Bluemel]

Madhur wrote:

On Jul 24, 2:24 pm, Mark Bluemel <mark_blue...@p obox.comwrote:

>>Madhur wrote:

>>>Thanks for the info...

Please don't top post.

>>>On Jul 24, 1:34 pm, Mark Bluemel <mark_blue...@p obox.comwrote:

>>>>I think you should tell us what you are trying to achieve in broader
terms - your original requirement - rather than telling us how you are
trying to do it.

>>>Array as referred above is list hundreds of user defined data types
and it is impossible for me to take care of it each time unless i have
an explicit hash maintained to it which i can not entertain right
now.. therefore I was looking for array of data types..which seems to
be impossible...

>>>Yes Enumeration is the only way to go..but is there any how i can link
an index to the enum data type...say enum looks like this

>>>typedef union enum1
{
type0,
type1,
type2,
type3
.
.
.
type n
}ENUM1;

>>>so if get an index say 2 can i extract type2 without using type2
explicity. .
in better way..is there somehow ican mention ENUM(2) and which should
get me type2????

I think you need an enumeration of types:-

enum TYPE {
INT,
LONG,
FLOAT,
DOUBLE,
...

};

A union of data values :-
union values {
int ival;
long lval;
float fval;
double dval;
..

};

And an array of structures :-

struct data_item {
enum TYPE type;
union values value;

};

struct data_item my_data[100];

Then you can use a switch to get the data for a particular data_item.
You could even have a really ugly macro -

#define ENUM(n) (my_data[n].type == INT)?my_data[n].value.ival: \
(my_data[n].type == LONG)?my_data[n].value.lval: \
...

Untested code etc...

But what is the data type of the variable which stores the result thus
returned...

God only knows. As my "Untested code" comment suggests, I only threw the
code together, I didn't analyse it. The macro approach may well not work
worth beans - indeed it may not even compile.

which brings again back to the question...

If you have to do what I think you are trying to do, I think you will
need some big switch statements to process the data appropriately to its
type. You cannot expect to handle different data types identically.

[Keith Thompson]

Madhur <ma********@gma il.comwrites:

I would like you help me in creating an array of data types.

I am interested in look at the the data type which looks like this
Array a[10]={int,float,cha r,int*......... ............... ......},

so that a[0] should return me int and a[1] should return me
float..which helps me in runtime type casting.

I do not know how to create such an array. If i create so what would
be the data type of "Array".
This is basically a variable to "data type" conversion.

Or is there any better way to do this.

C has no way to represent types at execution time. The only solution
is to keep track of it yourself. This is likely to be error-prone; if
a typo causes your program to treat something as an int when it should
be treated as a float, the compiler isn't going to tell you about the
error.

You might be able to reduce the risk of errors by writing a program to
generate some of your C code for you automatically.

Or you might be better off using a language other than C.

<OT>
C++ has something called RTTI (run-time type information). I've just
told you everything I know about it. I don't know whether it will
actually solve your problem. For more information, consult a C++ book
or tutorial, or Google it. Any questions should be directed to
comp.lang.c++, *not* here.
</OT>

<OT>
Other languages might also provide helpful features; you might try
comp.lang.misc or comp.programmin g.
</OT>

--
Keith Thompson (The_Other_Keit h) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <* <http://users.sdsc.edu/~kst>
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"

[Madhur]

On Jul 25, 12:13 am, Keith Thompson <[e-mail] rote:

Madhur <madhurr...@gma il.comwrites:

I would like you help me in creating an array of data types.

I am interested in look at the the data type which looks like this

Array a[10]={int,float,cha r,int*......... ............... ......},

so that a[0] should return me int and a[1] should return me
float..which helps me in runtime type casting.

I do not know how to create such an array. If i create so what would
be the data type of "Array".
This is basically a variable to "data type" conversion.

Or is there any better way to do this.

C has no way to represent types at execution time. The only solution
is to keep track of it yourself. This is likely to be error-prone; if
a typo causes your program to treat something as an int when it should
be treated as a float, the compiler isn't going to tell you about the
error.

You might be able to reduce the risk of errors by writing a program to
generate some of your C code for you automatically.

Or you might be better off using a language other than C.

<OT>
C++ has something called RTTI (run-time type information). I've just
told you everything I know about it. I don't know whether it will
actually solve your problem. For more information, consult a C++ book
or tutorial, or Google it. Any questions should be directed to
comp.lang.c++, *not* here.
</OT>

<OT>
Other languages might also provide helpful features; you might try
comp.lang.misc or comp.programmin g.
</OT>

--
Keith Thompson (The_Other_Keit h) [e-mail] <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <* <http://users.sdsc.edu/~kst>
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"

RTTI functionality can not be thought of in C, as C doesn't care about
the objects being created.
Hence the concepts of typeid does not work.
It would have been good to implement RTTI functionality in C too..
My problem has no solution in C but has in C++..

[santosh]

Madhur wrote:

On Jul 25, 12:13 am, Keith Thompson <[e-mail] rote:

<snip>

>--
Keith Thompson (The_Other_Keit h) [e-mail]
<http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*>
<http://users.sdsc.edu/~kst>
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"

Don't quote signatures unless you're commenting on them.

RTTI functionality can not be thought of in C, as C doesn't care about
the objects being created.
Hence the concepts of typeid does not work.
It would have been good to implement RTTI functionality in C too..
My problem has no solution in C but has in C++..

Err, and your question?