Is this a reasonable use of the ternary operator? [closed]

Answer 1

I think that sometimes the ternary are a necessary evil in initializer lists for constructors. I use them mostly for constructors where I want to allocate memory and set some pointer to point at it before the body of the constructor.

An example, suppose you had an integer storage class that you wanted to have take a vector as an input but the internal representation is an array:

class foo
{
public:
    foo(std::vector<int> input);
private:
    int* array;
    unsigned int size;
};

foo:foo(std::vector<int> input):size(input.size()), array( (input.size()==0)?
        NULL : new int[input.size])
{
    //code to copy elements and do other start up goes here
}

This is how I use the ternary operator. I don't think it is as confusing as some people do but I do think that one should limit how much they use it.

Answer 2

If you have multiple method invocations in one or both of the tenary arguments then its wrong. All lines of code regardless of what statement should be short and simple, ideally not compounded.

Answer 3

Compilers these days will make an if as fast as a ternary operator.

You goal should be how easy is it for another software developer to read.

I vote for

if ( inVar != 0 )
{
   v.push_back( inVar );
}

why the brackets...because one day you may want to put something else in there and the brackets are pre-done for you. Most editors these days will put them in anyway.

Answer 4

The ternary is a good thing, and I generally promote it's usage.

What you're doing here however tarnishes it's credibility. It's shorter, yes, but it's needlessly complicated.

Answer 5

I use ternary operator when I need to call some function with conditional arguments - in this case it is better then if.

Compare:

printf("%s while executing SQL: %s",
        is_sql_err() ? "Error" : "Warning", sql_msg());

with

if (is_sql_err())
    printf("Error while executing SQL: %s", sql_msg());
else
    printf("Warning while executing SQL: %s", sql_msg());

I find the former is more appealing. And it complies to DRY principle, unlike latter - you don't need to write two nearly identical lines.

Answer 6

Most of the tortured ternaries (how's that for alliteration?) I see are merely attempts at putting logic that really belongs in an if statement in a place where an if statement doesn't belong or can't go.

For instance:

if (inVar1 != 0)
  v.push_back(inVar1);
if (inVar2 != 0)
  v.push_back(inVar2);

works assuming that v.push_back is void, but what if it's returning a value that needs to get passed to another function? In that case, it would have to look something like this:

SomeType st;
if (inVar1 != 0)
  st = v.push_back(inVar1);
else if (inVar2 != 0)
  st = v.push_back(inVar2);
SomeFunc(st);

But that's more to digest for such a simple piece of code. My solution: define another function.

SomeType GetST(V v, int inVar1, int inVar2){
    if (inVar1 != 0)
      return v.push_back(inVar1);
    if (inVar2 != 0)
      return v.push_back(inVar2);        
}

//elsewhere
SomeFunc(GetST(V v, inVar1, inVar2));

At any rate, the point is this: if you have some logic that's too tortured for a ternary but will clutter up your code if it's put in an if statement, put it somewhere else!