rfgrgf, stupid pointers

**jverkoey** · 04-10-2003

yes, this is another pointer question

ok, here's my code:

Code:

#include <iostream.h>
#include <math.h>  //edit, forgot to add this :)

void ModifyPointer(double* value, bool*ok)  // forgot the void, too
{
value=sin(45);
ok=true;
}

void main()
{
double temp1;
bool temp2;

ModifyPointer(&temp1,&temp2);
cout << temp1 << " is " << temp2 << endl;
}

now, theoretically, that would make it so that temp1 and temp2 are equal to sin of 45 and true (respectively). Thing is, when I try and compile this, it returns an error:

error C2440: '=' : cannot convert from 'double' to 'double *'

and that ONLY happens for the sin one, it doesn't happen for the bool one. Now, i've tried MANY things (from reinterprets, to just plain (double *), and none of the options i've tried so far have worked....)

so i need to know why this isn't working, and how i can fix it.

NOTE: the above isn't my actual code, it's just pseudo code in case you haven't noticed, but it should compile and generate the error i think

thanks in advance.

**jverkoey** · 04-10-2003

ok, i'm stupid, rgfgrfggrgf

found out that because i was using this in a switch statement that for some reason it wouldn't work right.........

so i just made them equal temp variables, and when i got out of the switch, just assigned the temp vars to the pointers, and now it works

but now, i'm trying to assign them as such:

*ok=temp;

but when i assign the value, the program crashes (lol), now i'm really confused

**jverkoey** · 04-10-2003

screw it, i'm just going to make the variables global (as much as i don't want to) but C++ is really pi$$ing me off right now

so if anyone figures this out, just reply here, but otherwise, i'm moving on

**Stoned_Coder** · 04-10-2003

Dear oh dear the error tells you what you are doing. maybe you should read the faq pointers article.
You are assigning a double to a pointer to a double.

value=sin(45);

lets look at the types

double* = double;

see the problem?

The faq pointer tut will fix it for you.

**Speedy5** · 04-10-2003

After reading the tutorial on pointers note that there is another way to do this: using references. Next, use int main (void main?????). Oh yea, use the newer headers.

Code:

#include <iostream>
#include <cmath>
using namespace std;

void ModifyPointer(double &value, bool &ok)
{
   value = sin(45);
   ok = true;
}

int main()
{
   double temp1 = 0;
   bool temp2 = false;

   ModifyPointer(temp1, temp2);
   cout << temp1 << " is " << temp2 << endl;

   return 0;
}

**Speedy5** · 04-10-2003

Originally posted by jverkoey
but now, i'm trying to assign them as such:

*ok=temp;

but when i assign the value, the program crashes (lol), now i'm really confused

Thats because the ok pointer is probably invalid as in you never set it to anything useful. A "crazy pointer."

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