if...

its not that I dont get how to use it but i'm just wondering why is it that for example if I had abc as a variable that

Code:

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if (abc==!4)

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wont work(well it does but if I entered in anything it assumes its false and goes onto the else statement)? since ! takes precedence shouldnt it be read
not 4 > == > abc and when reconstructed isnt it saying that if abc is equal to not 4 then?
I tried

Code:

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if (!(abc==4))

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and it worked but isnt it sortve the same as the if statement before just reworded to if its not equal to 4?

!4 equates to 0.
so the first test is abc == 0

the second test is completely different.
First abc == 4
then "not" the result.

oh, how does !4 equate to 0 though, i still dont really get it
Now I have another problem with the loops, is FOR the same as WHILE except you can do more things variable wise with FOR? It seems pretty much the same and I tried adding a loop to:

Code:

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#include <iostream>
int main()
{
    int a;
    std::cout<<"What is 2+2?"<<std::endl;
    std::cin>>a;
    if(!(a==4))
{
        std::cout<<"That would be correct my fellow mathematician."<<std::endl;
        system ("PAUSE");
}
    else
{
        std::cout<<"wrong!"<<std::endl;
        system ("PAUSE");
}
    return 0;
}

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so i put

Code:

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while(!(a==4))

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before cout so it can ask the question again but the question just keeps getting asked and loops over and over, is there a way to make it not do that or would I have to create another variable and add a AND statement to the while code?

I don't know if the following is your confusion (just wondering),
if not then nevermind...

Code:

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expression (abc==!4)  is equal (!(abc==4))  // eek, wrong
expression (abc!= 4)  is equal (!(abc==4))  // eek, right

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Make sure that you capture the input in the while loop as well:

Code:

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while(a != 4)
{
  std::cout << "...";
  std::cin >> a;
}

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Quote:

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oh, how does !4 equate to 0 though, i still dont really get it

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Well, think about how if(x) works... if x is non-zero the code following will execute. If x is zero, then the code following will not execute.

if(4); //Always "true"
if(!4); // Always "flase" , so the stuff inside the parenthesis must be zero!

A logical NOT !X is different from a bitwise NOT ~X. This: ~4 does not evaluate to zero.

here's another way to think about it... when you just put if(constant), it kinda acts like this: if(constant==constant) which it always will, in your case, it would be if(4==4), and in your implementation if(!a), it would be similar to if(!a==a), which it doesn't...

I like DougDbug's answer. AFAIK, all conditional statements need to be phrased in a true/not-true dichotomy. In C++ zero equates to false (not-true), and any non-zero values equate to true. Therefore if you say:

if(4)

then 4 is non-zero so it is interpretted by the compiler as saying if(true). If you say:

if(!4)

then the compiler probably first converts the statement to this:

if(!true)

and then to this:

if(false)

which is the same as this

if(0)

so in the end !4 == 0 when used as a conditional. Logically !4 could mean the value could be anything but 4 like -100 or 0 or 3, but when used as a conditional, !4 means 0, given the need for results that equate to either true or not-true.

I still cant get the loop working but I understand the !4 thing equating to 0 now, thanks, and btw the program is supposed to be a joke type thing where 2+2 equals anything except 4 :P

Post the code that you have so far, please