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lvalue required as left operand of assignment

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# 1  
Old 10-22-2011
lvalue required as left operand of assignment
Code:
z < 0 ? z= z + 2*r*cos(theta) : z= z - 2*r*cos(theta);


Does anyone know what is wrong here?
I've got compiler msg:
lvalue required as left operand of assignment

All variables are "double". I'm using gcc compiler (but I don't think that matters)
# 2  
Old 10-22-2011
I think what you are intending is this:

Code:
z += z < 0 ? 2*r*cos(theta) : -2*r*cos(theta);

Which adds 2*r*cos(theta) to z if z < 0 and subtracts 2*r*cos(theta); from z if z is >= than 0;
Last edited by agama; 10-22-2011 at 12:54 PM.. Reason: fixed small typo
This User Gave Thanks to agama For This Post:
EmilyTheStrange
# 3  
Old 10-22-2011
I think you don't entirely understand the operator that you are using. Try this:
Code:
z = z < 0 ?z + 2*r*cos(theta) : z - 2*r*cos(theta);

# 4  
Old 10-22-2011
Code:
z = (z < 0) ? z + 2*r*cos(theta) : z - 2*r*cos(theta);

Or, if you'd like:
Code:
z += (z < 0) ? 2*r*cos(theta) : -2*r*cos(theta);

edit: ugh; beaten, twice over, lol.
# 5  
Old 10-22-2011
It can be shorter.

Code:
z += (z < 0 ? 2 : -2 ) * r * cos(theta);

Last edited by MacMonster; 10-22-2011 at 01:25 PM.. Reason: Fix a typo.
This User Gave Thanks to MacMonster For This Post:
EmilyTheStrange
# 6  
Old 10-22-2011
Thank u. I think I do understand my mistake now. Smilie
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