error: non-lvalue in assignment

muby

Hi Everybody

the compiler throws an error when it runs this function in my code, I couldn't figure out what is wrong with my code, please assist me, thanks :).

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 void SMAC::IncreaseCW() {

init rI=2;

DATA_CW=DATA_CW*rI;

double cw = (Random::random() % DATA_CW) * slotTime_sec_;

mhCS_.sched(CLKTICK2SEC(difs_) + cw);

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 mac/smac.cc: In member function `void SMAC::IncreaseCW()':

mac/smac.cc:463: error: non-lvalue in assignment

Banfa

Quote:

init rI=2;

Did you mean int?

JosAH

Quote:

Originally Posted by Banfa

Did you mean int?

DATA_CW suggests to be a macro name ... who knows?

kind regards,

Jos

muby

sorry folks, i meant

Quote:

int rI = 2;

im still facing the same error, any help? thx :)

scruggsy

Your error says line 463. Which of those lines is 463?

You have an assignment involving something called DATA_CW, but you didn't post the code which defines DATA_CW.

More info == more help.

JosAH

Quote:

Originally Posted by muby

sorry folks, i meant

im still facing the same error, any help? thx :)

Did you read the error message and did you check the line your compiler complained about? Learn how to read error messages; it'll be a lot faster than posting here everytime you see one.

kind regards,

Jos

muby

Thanks for your reply, the line where im getting error is shown below,
I defined DATA_CW in header file as

Quote:

#define DATA_CW 63

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 # void SMAC::IncreaseCW() {

# int rI=2;

# DATA_CW=DATA_CW*rI; # error is in this line (line 463)

# double cw = (Random::random() % DATA_CW) * slotTime_sec_;

# mhCS_.sched(CLKTICK2SEC(difs_) + cw);

}

newb16

After preprocessing it's expanded to
63 = 63*2;

Left part is a number here, you can't assign to numbers. What are you trying to do?

muby

IncreaseCW should increases the value of DATA_CW by doubling the old value of DATA_CW, and assigne the new value back to DATA_CW. this new value will be used in other functions.

I changed it as shown below, but im still getting the same error.

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 void SMAC::IncreaseCW() {

int DATA_CW_new;

DATA_CW_new = (DATA_CW*rateincrease);

DATA_CW = DATA_CW_new;

double cw = (Random::random() % DATA_CW) * slotTime_sec_;

mhCS_.sched(CLKTICK2SEC(difs_) + cw);

}

scruggsy

Read newb16's post again.
DATA_CW is a macro, not a variable. It is replaced by the compiler with '63' wherever it occurs in your code. You cannot assign to it. Use a variable.