? - Operator issue - checks wrongly

[ARMinius]

Hi,

I want to avoid if/else, therefore use the ? operator
aA is an int, looped from 0 to 10:

dD=(aA==aA^aA^0)?12:(aA==1)?23:(aA==2||aA==3||aA==9)?34:(aA==4||aA==7)?45:(aA==5)?56:(aA==6)?67:(aA==8)?78:(aA==10)?89:90;

Ouput: :(

aA = 0 --> dD = 12
aA = 1 --> dD = 23
aA = 2 --> dD = 12
aA = 3 --> dD = 12
aA = 4 --> dD = 12
aA = 5--> dD = 12
aA = 6 --> dD = 12
aA = 7 --> dD = 12
aA = 8 --> dD = 12
aA = 9 --> dD = 12
aA = 10 --> dD = 12

Please help me,

greetings,

Lukas

[vlad from moscow]

What does subexpression aA^aA^0 mean? It is always equal to 0.

[m4ster r0shi]

What values do you think this takes? -> aA == aA ^ aA ^ 0

What values does it actually take?

Useful link -> http://en.cppreference.com/w/cpp/language/operator_precedence

[ARMinius]

Sorry, yes, I wanted to obfuscate the program, I forgot to remove this bit, yes, it's 0.

dD=(aA==0)?12:(aA==1)?23:(aA==2||aA==3||aA==9)?34:(aA==4||aA==7)?45:(aA==5)?56:(aA==6)?67:(aA==8)?78:(aA==10)?89:90;

is the code that gets executed ... but it doesn't work, does anyone know, why?

This is gonna be a small exercise for ur mind ...

[m4ster r0shi]

it doesn't work

What do you mean?

[ARMinius]

Output:

aA = 0 --> dD = 12
aA = 1 --> dD = 23
aA = 2 --> dD = 12
aA = 3 --> dD = 12
aA = 4 --> dD = 12
aA = 5 --> dD = 12
aA = 6 --> dD = 12
aA = 7 --> dD = 12
aA = 8 --> dD = 12
aA = 9 --> dD = 12
aA = 10 --> dD = 12

Expected Output:

aA = 0 --> dD = 12
aA = 1 --> dD = 23
aA = 2 --> dD = 34
aA = 3 --> dD = 34
aA = 4 --> dD = 45
aA = 5 --> dD = 56
aA = 6 --> dD = 67
aA = 7 --> dD = 45
aA = 8 --> dD = 78
aA = 9 --> dD = 34
aA = 10 --> dD = 89

[m4ster r0shi]

Ok. So, what's the problem? -> http://ideone.com/8Iz3dN

[ARMinius]

WTF !! It doesn't work for me if i choose other values !!

try

int dD=(aA==aA^aA^0)?72:(aA==1)?101:(aA==2||aA==3||aA==9)?108:(aA==4||aA==7)?111:(aA==5)?32:(aA==6)?87:(aA==8)?114:(aA==10)?100:33;

[ARMinius]

I now already spent hours in trying to spot the difference ... i can't !! wtf...

I'm totally confused

[JLBorges]

> I'm totally confused

What else do you expect with code like this?
dD=(aA==aA^aA^0)?12:(aA==1)?23:(aA==2||aA==3||aA==9)?34:(aA==4||aA==7)?45:(aA==5)?56:(aA==6)?67:(aA==8)?78:(aA==10)?89:90;

I too am totally confused.

[m4ster r0shi]

I now already spent hours in trying to spot the difference

Since you're having such a hard time spotting the problem, I'll give you one more hint:
Try this -> (aA==(aA^aA^0)) instead of this -> (aA==aA^aA^0) and verify that it works.

Then, read my first post carefully in order to understand why it works.

[Cheraphy]

It'll take forever, but write out the truth table for each of these comparisons for each iteration. It should become apparent what you're doing wrong.

[ARMinius]

Thank ya, m4ster !1!! *takes a bow and kisses your feet, blabla*
Your first post?

What values do you think this takes? -> aA == aA ^ aA ^ 0

What values does it actually take?

Useful link -> http://en.cppreference.com/w/cpp/language/operator_precedence

Hmmm... At first I couldn't use this link, but do ya mean "from left to right" of the link? :O

Thanks, THAT is somehow the difference ... :( I'm ashamed (Do I have to? I guess so...)

I too am totally confused.

Thanks soooo much for this comment,JLBorges ,I'm feeling a bit better now :D

Lukas

[m4ster r0shi]

What I mean is that the == operator has higher precedence than the ^ operator.

It follows that this -> (aA == aA ^ aA ^ 0) is the same as this -> ((aA == aA) ^ aA ^ 0), which is the
same as this -> (1 ^ aA ^ 0), which is false if aA is 1 and true otherwise, which is not what you want.

[ARMinius]

aaaaah, k, thx for clarifying :)