std::logic_error instead of return false

Question

I am looking for someones opinion about the usage of std::logic_error instead of using a complicated list of nested if/elseif return true/false.

I would like to move from a lot of similar function like the one below

bool validate_data(){
    std::vector<int> v; 
    //fill with data
    if( v.find(10) == v.end() ){
       return false;
    } 
    // other checks that return false
}

to

bool validate_data(){
    std::vector<int> v; 
    //fill with data
    if( v.find(10) == v.end() ){
       throw std::logic_error("error message");
    } 
    // other checks that return false
}

and call all this list of functions in a single try-catch block.

Since it is a derived from std::exception probably I don't know if it is a good idea.

Is anyone using like the example below?

Thanks a lot

AFG

Answer 1

You should only use exceptions for exceptional circumstances. Using (and checking) return values is far more efficient when the chances of it being true or false are non-trivial. Exceptions are more efficient only when the chance of throwing is so small as to out-weigh the cost of the return-value check.

So if the chances of invalid data are very very low, then go with exceptions. Otherwise, the current solution should not only be fine, but slightly more efficient as well (As throwing and handling is relatively expensive).

Answer 2

Only use exceptions for exceptional situations.

Is not finding the value 10 an exceptional situation? Or is it just a normal situation?

Renaming your method from validate_data to is_data_valid makes it much clearer. If the method returns true, it's valid. If it returns false, it isn't. No need to use exceptions for this.

Answer 3

Since your function is called validate_data() I'd only throw an exception if there is any internal error within the function and use true or false to indicate that the function did validate the input, but it was either valid (return true) or invalid (return false).

This will not prevent you from having multiple if() else if() else constructs but it will make the code cleaner and easier to distinguish if the data were invalid or an internal error happened.

try {
  bool valid = validate_data(foo);
  /* process data or break if invalid */
} catch (std::exception &ex) {
  /* internal error happened */
}

as you can see it will make your code longer, IMHO cleaner.