In these exercises I am using Visual Studio 2017 and the std_lib_facilities header provided by Stroustrup.
Chapter 19 // Drill 14
Bonus: Define input and output operators (>> and <<) for vector<T>s. For both input and output use a { val, val, val } format. That will allow read_val() to also handle the S<vector<int>> variable.
This drill. I was like "sure no probs". Had it working perfectly for ints and then I remembered that this function can take in vectors of any type. Throw strings, floats, chars etc., at it and it breaks spectacularly. I then had to reset my brain to get into the mindset of generic programming...You need to think of everything and anything that could happen.
Apart from not being able to handle vectors of custom types (what a nightmare), it also doesn't handle strings with spaces in them. But I'm pretty happy with this. He chose this input/output specifically because it's really annoying. Bjarne is the true sneaky fox. If you needed very specific string output though I don't think you would use generic types.
For this it checks if there are any undesirable characters and if not, it then reads the entire entry into a string. It removes commas from the string then converts it to a stringstream to be read into the templated type. This way, we don't have to bother with string to random type conversions; stringstream will take care of it for us. It also has the advantage of reading the entire variable in. So { 1.77, 5 } will be read as:
- cin >> string, ignore { and ' '
- cin >> string (reads 1.77, )
- removes the comma
- stringstream >> type ( 1.77 is converted to type )
- push value into vector
- cin >> string, ignore space
- cin >> string ( reads 5 )
- no comma to remove
- stringstream >> type ( 5 is converted to type )
- push value into vector
- cin >> string, ignore space
- cin >> string, } read, break out of loop and return
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