storing static data of variable types

[Gernot Frisch]

Hi,

I've got to write a BASIC to C++ converter and came across the problem of
the DATA statement.

I must provide a way of storing:
DATA 5.123, "abc", ...
in C++.

my first guess was this:

struct
{
double* pD;
const char* pC;
} str[2]={
{NULL, "xy"},
{&123.4, NULL},
};


but &123.4 is not possible. Now, having temporary global variables for this
doesn't make me too happy either.

Is there a "clean" way of doing this?


--
------------------------------------
Gernot Frisch

http://www.glbasic.com

[Ian Collins]

Re: storing static data of variable types

Gernot Frisch wrote:

Hi,
>
I've got to write a BASIC to C++ converter and came across the problem
of the DATA statement.
>
I must provide a way of storing:
DATA 5.123, "abc", ...
in C++.
>
my first guess was this:
>
struct
{
double* pD;
const char* pC;
} str[2]={
{NULL, "xy"},
{&123.4, NULL},
};
>
>
but &123.4 is not possible. Now, having temporary global variables for
this doesn't make me too happy either.
>
Is there a "clean" way of doing this?
>

Store the values as strings and convert then back as required?

--
Ian Collins.

[Michael DOUBEZ]

Re: storing static data of variable types

Gernot Frisch a écrit :

Hi,
>
I've got to write a BASIC to C++ converter and came across the problem
of the DATA statement.
>
I must provide a way of storing:
DATA 5.123, "abc", ...
in C++.
>
my first guess was this:
>
struct
{
double* pD;
const char* pC;
} str[2]={
{NULL, "xy"},
{&123.4, NULL},
};
>
>
but &123.4 is not possible. Now, having temporary global variables for
this doesn't make me too happy either.
>
Is there a "clean" way of doing this?

Directly stores the value instead:

struct
{
double pD;
const char* pC;
}str[2]={
{NULL, "xy"},
{123.4, NULL},
};

Michael

[Gernot Frisch]

Re: storing static data of variable types

Directly stores the value instead:
>
struct
{
double pD;
const char* pC;
}str[2]={
{NULL, "xy"},
{123.4, NULL},
};

First I thought I'd store twice the ammount hten. But thinking of it, my way
I'd store the number _plus_ a pointer to it. I'm so stupid.
Thank you for showing me :)

[Michael DOUBEZ]

Re: storing static data of variable types

Gernot Frisch a écrit :

>
>

>Directly stores the value instead:
>>
>struct
>{
> double pD;
> const char* pC;
>}str[2]={
> {NULL, "xy"},
> {123.4, NULL},
> };

>
>
First I thought I'd store twice the ammount hten. But thinking of it, my
way I'd store the number _plus_ a pointer to it. I'm so stupid.
Thank you for showing me :)
>

If memory space is an issue, you could use a union (and a type tag to
retrieve the relevant information).

It is common in many interpreters written in C:
struct
{
int type; //give the type of data
union
{
const char* m_string;
double m_double;
long m_integer;
//...
} data;
}

Nowadays, I think there is Boost.Variant that simplifies this much but I
have no experience with it. Perhaps worth a look.

Michael

[Gernot Frisch]

Re: storing static data of variable types

DATA 123.4, "xy" translates to:
>
static Data data[] = { Data( 123.4 ), Data( "xy" ) /* , ... */ };
Repository MyData( &data[0], &data[sizeof(data) / sizeof(Data)] );

I did something similar already. Thank you for your time and help.
For the Read, I just overloaded 2 functions:
void READ(MyNumber& dbl);
void READ(MyString& str);