Posts tagged ‘ternary’

C++ is bad: problems with the ternary operator, addendum

I’ve found another interesting wrinkle in the ternary operator. So, here’s a bonus question for that quiz from last time. You start with the following code:

class Abstract;
class DerivedOne;  // Inherits from Abstract
class DerivedTwo;  // Inherits from Abstract
Abstract x;
DerivedOne one;
DerivedTwo two;
bool test;

Again, you can assume that all of these are defined/initialized (and you can assume the comments are correct—both Derived* classes inherit from Abstract). Now, consider these snippets:

# Code Snippet
A
Code Snippet
B
Bonus
if (test) x = one;
else x = two;
x = (test ? one : two);
 


If you read the previous installment, you’ve probably guessed by now that these are not equivalent, and you’d be right. In what ways do they differ?

Another unexpected answer →

C++ is bad: problems with the ternary operator

In today’s installment of “why not to program in C++,” I give you the following quiz, which Dustin, Steve, Tom, and I had to figure out today (Dustin’s code was doing the weirdest things, and we eventually traced it down to this):

Suppose you start out with the following code:

class Argument;
Argument x;
void Foo(const Argument& arg);
bool test;

You can assume that all of these are defined/initialized elsewhere in the code. For each pair of code snippets below, decide whether the two snippets are equivalent to each other.

# Code Snippet
A
Code Snippet
B
1
if (test) Foo(x);
else Foo(Argument());
Foo(test ? x : Argument());
 
2
{ // limit the scope of y
  Argument y;
  Foo(test ? x : y);
}
Foo(test ? x : Argument());
 
 
 
3
Foo(x);
Foo(test ? x : x);
4
Foo(x);
Foo(true ? x : Argument());


Edit: what I meant by the curly braces in Question 2 is that you shouldn’t consider “y is now a defined variable” to be a significant difference between the two snippets.

The answers are worse than you'd think. →