How to execute / evaluate a string expression? (from newbie)

[Marco Traverso]

Hi all,

Is there a function to evaluate a string expression?
InVisual Basic and VbScript there is the Execute command that does this job.

For example:

Dim a,x
a=100
Execute "x = a/2"

Now the x value is 50...

Is there anything of this kind in C++/Visual C++ ?
Or do I need an external math parser or function?

Thank you in advance,

Marco

 

[Grant Austin]

Dim a,x

a=100
Execute "x = a/2"

Now the x value is 50...

Is there anything of this kind in C++/Visual C++ ?
Or do I need an external math parser or function?

I don't believe there is a way to execute strings unless someone has
developed an additional library to do such. I suppose you could always
write/use a lexical analyzer or a lot of string functions to do the parsing.

Unless you're expecting the user to type in expressions, the 'normal' way
is to do something like this:

void somefun(){
...
...
...
int a,x;
a = 100;
x = a/2;
/*
if you have stdio or iostream #include'd output by
printf("x = %d",x); or cout << "x = " << x; respectively
*/
}

I hope that helps,
Grant

 

[Marco Traverso]

Hi Grant,

Unless you're expecting the user to type in expressions, the 'normal' way
is to do something like this:

Unfortunately I need just that! Anyway, since I'm writing a plug-in for an
app that includes vbscript, I will launch a little script with the execute
command and then take back the result into C++.

Thank you for the clarification!

Regards,

Marco

 

[Grant Austin]

A possible solution occurred to me. You can embed TCL into any c/c++
program. This might allow you to evaluate the expressions you need.

There might be other scripting languages in that direction as well.

-Grant

 

[Marco Traverso]

Hi Grant,

Even if it is not so clear to me (I'm a VC++ newvie, see subject ;-)),
anyway I'll go through that!

Thanks again!

Marco

 

[Gianni Mariani]

Hi Grant,

Even if it is not so clear to me (I'm a VC++ newvie, see subject ;-)),
anyway I'll go through that!

There exist a number of interpreters that are embeddable in C++.

TCL is but one.

 

[lallous]

Hi Grant,

Even if it is not so clear to me (I'm a VC++ newvie, see subject ;-)),
anyway I'll go through that!

Thanks again!

Marco

Guess you can use VBScript/Scripting engine from your win32 app.
Try asking your question in one of Microsoft's programming / scripting
newsgroup.

Regards,
Elias

 

[Marco Traverso]

Thany you all!

I think I've found a solution with the winapp vbscript engine!

Regards,

Marco