complex if statement readability

[mlupo]

what is the best way to make something like this more readable?
is there a standard for complex if's like this one??

if((!ki.fname || ki.fname[0]=='0')&& ki.id==0)
  if(((!ki.sender ||  ki.sender[0]=='0') || 
  strcmp(ki.sender,curr->sender)==0)  &&  
  ((!ki.addressee || ki.addressee[0]=='0') || 
  strcmp(ki.addressee,curr->addressee)==0) &&
  ((!ki.regarding || ki.regarding[0]=='0') || 
  strcmp(ki.regarding,curr->regarding)==0) &&
  (ki.date.day == 0 || ki.date.day == curr->date.day) &&
  (ki.date.month == 0 || ki.date.month == curr->date.month) &&
  (ki.date.year == 0 || ki.date.year == curr->date.year)) 
  {
    hits->next=copynode(curr);
    hits=hits->next;		//bump pointer
  }

[QuestionC]

When writitng very complicated nested paranthesis, I just try to indent in the same manner as if I were nesting functions. I'm also not a big fan of using short lines, so it makes things easier to write, personally (althouh it turns out ugly when printed). Also, you could cut down on the number of paranthesis if you're comfortable with precedence and associativity.

if
(
 (!ki.fname || ki.fname[0]=='0') &&
 (ki.id ==0) &&
 (!ki.sender ||  ki.sender[0]=='0' || strcmp(ki.sender,curr->sender)==0)  &&
 (!ki.addressee || ki.addressee[0]=='0' || strcmp (ki.addressee,curr->addressee)==0) &&
 (!ki.regarding || ki.regarding[0]=='0' || strcmp(ki.regarding,curr->regarding)==0) &&
 (ki.date.day == 0 || ki.date.day == curr->date.day) &&
 (ki.date.month == 0 || ki.date.month == curr->date.month) &&
 (ki.date.year == 0 || ki.date.year == curr->date.year)
)
{
 hits->next=copynode(curr);
 hits=hits->next;		//bump pointer
}

Although something I have to ask about this code, you're using things like !ki.sender, which makes sense if the pointer may be initialized to NULL, however NULL is not neccisarily 0. If you're intending to do something equivalent to ki.sender != NULL, I suggest you do so that a way. Also, I eliminated the nested if because... well, it could be done with one if, and that matched better.

[Salem]

> is there a standard for complex if's like this one??
Tricky - there's good formatting as suggested by QuestionC. Good formatting never goes amiss.

You could try several local variables...
t1 = (!ki.fname || ki.fname[0]=='0');
t2 = (ki.id ==0);
t3 = (!ki.sender || ki.sender[0]=='0' || strcmp(ki.sender,curr->sender)==0);
...
if ( t1 && t2 && t3 )

It's not strictly the same code, since && and || have short circuit evaluation (if t1 is false, t2 is not evaluated). But with several discrete expressions, they are all evaluated.

This might not be a problem here, but in some cases it could be.

The other advantage is that you can use the debugger to look at t1, t2 etc, to see why your test starts failing mysteriously.


> however NULL is not neccisarily 0.
http://www.eskimo.com/~scs/C-faq/q5.5.html

[QuestionC]

I stand corrected... although if I rewrote C, I think I'd take that rule out.