if statement confusion

[Swoorup]

I have a condition and I would like to instead change the condition so that it would execute the previous statements after else statement.

It seems hard to explain but I'll try my best to illustrate anyway

if (condition)
<statement1>
else
<statement2>

So I would like to change the condition so that

if (condition)
<statement2>
else
<statement1>

And the condition is

if(!lightStateAtNextLink || !bIsLightEnAtConnection && nLinkNext.IndexToAttachedNode() != pVeh->_.stAutopilot.m_dwNextNode || bIsLightEnAtConnection && nLinkNext.IndexToAttachedNode() == pVeh->_.stAutopilot.m_dwNextNode)

And I have changed that to this. Is this correct?

if(lightStateAtNextLink && bIsLightEnAtConnection || nLinkNext.IndexToAttachedNode() == pVeh->_.stAutopilot.m_dwNextNode && !bIsLightEnAtConnection || nLinkNext.IndexToAttachedNode() != pVeh->_.stAutopilot.m_dwNextNode)

[whiteflags]

Well, no. If the first condition is correct then you have to negate the whole thing to flip the result. We end up with:

if( !(!lightStateAtNextLink || !bIsLightEnAtConnection && nLinkNext.IndexToAttachedNode() != pVeh->_.stAutopilot.m_dwNextNode || bIsLightEnAtConnection && nLinkNext.IndexToAttachedNode() == pVeh->_.stAutopilot.m_dwNextNode) )

[grumpy]

No.

You're not accounting for the fact that && has higher precedence than ||. Because of that it is not just a case of negating individual expressions and swapping && and ||.

[Swoorup]

Thanks guys!
How do I go on manipulating individual condition though?

[rogster001]

Not sure what you mean but looking at your other examples you should use parentheses to encapsulate expressions within the overall evaluation

[Cat]

1. If you want to invert the condition, you can just put the whole thing in parentheses and add a ! at the beginning.

2. As mentioned, by DeMorgan's law, inverting a boolean expression is possible if you invert every individual condition, change all || to && and vice versa, AND use parentheses to ensure order of operations is the same as initially.

So if you wanted to invert 'A && B || C', you could write either:
!(A && B || C)
or
(!A || !B) && !C

because && has higher precedence than ||, so to keep order of operations the same, parentheses are added.

3. Really, though, if you're going to calculate this whole thing (including multiple function calls), why not just store the result of the expression in a boolean variable and then just invert it for your second loop? That also means any changes to the expression can be very easily done in one place.