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"expect a constant expression"

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Join Date: Apr 2009

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Re: "expect a constant expression"

#11

Apr 17th, 2009

You know, I just found out that IT IS POSSIBLE to do it my way, but it wont accept the way I calculate the "int"

I tested it with this:

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const int test1 = 10/5; //even number without having to round up
 
double test2_calc = (double)10/(double)5;
const int test2 = (int)test2_calc;
 
char mychar[test1][ANOTHER_CONSTANT]; //Works
char mychar[test2][ANOTHER_CONSTANT]; //Doesn't work
const int test1 = 10/5; //even number without having to round up

double test2_calc = (double)10/(double)5;
const int test2 = (int)test2_calc;

char mychar[test1][ANOTHER_CONSTANT]; //Works
char mychar[test2][ANOTHER_CONSTANT]; //Doesn't work

So, in light of this new information. How do I BEST CALCULATE that?

like, rounding up without having to convert to double?

I also think I need a lecture on casts, 'cause maybe I'm not handling them right...

Last edited by ShadowScripter; Apr 17th, 2009 at 10:01 pm.

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Re: "expect a constant expression"

#12

Apr 18th, 2009

You can only do that when they are defined as constants, so MSVC++ can create the 2D arrays at compile time rather then at runtime.

I suggest reading how to make your own 2D arrays, or using vectors.

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Re: "expect a constant expression"

#13

Apr 19th, 2009

Why are you using old casting ?

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Originally Posted by ShadowScripter

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double test2_calc = (double)10/(double)5;
const int test2 = (int)test2_calc;
double test2_calc = (double)10/(double)5; const int test2 = (int)test2_calc;

It's a better practice to use the new casting operators to do conversion between datatypes:

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double num = 5.23;
int num2 = static_cast<int>(num);

instead of the old ones:

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double num = 5.23;
int num2 = (int)num;

Last edited by tux4life; Apr 19th, 2009 at 7:41 am.

"Never argue with idiots, they just drag you down to their level and then beat you with experience."

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Re: "expect a constant expression"

#14

Apr 19th, 2009

See here why: http://www.informit.com/guides/conte...lus&seqNum=134

Boils down to C-style casts being static_casts or reinterpret_casts. But I never got reinterpret_cast to work anyway.

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Re: "expect a constant expression"

#15

Apr 19th, 2009

See, now this is why I love these forums! You are all willing to share your knowledge (albeit most knowledge passed on to you by others as well). I didn't know about static_cast, because I rely most of my work on the C++ Beginner's Guide written by the Microsoft Corporation, I guess it's not up to date... either that or I missed static_cast entirely

Still tho, the answer to my original question remains unclear, well, I did get some suggestions from Clockowl about vectors, but they were much too confusing and I would ask you to explain them in a more easier way for me to understand, but that is for another thread.

At one time I thought about using pointers, during these 2 days since I posted my problem I have grown to learn more about the power of pointers. I managed to create a pretty good converter function, more specifically a Char To String, AND, a String to Char! I don't know if it already exists or is unnecessary, but it sure was fun!