The WordArrayT

Objectives

1. Implement a static array to hold words.

Notes

• We discussed a static array of WordCountT in our initial design
  • Data:
    • size_t size, capacity
    • WordCountT data[MAX_WORDS]
  • Methods:
    • constructor
    • Size - to get the current elements
    • Capacity - to get the capacity
    • PushBack(WordCountT) to add a word
    • [] to access the array
    • at to access the array
  • Take a look at WordArrayT.h.
    • Note: using DataT = WordCountT;
      • This makes DataT a nickname for WordCountT
      • This makes it generic so I can change the data type by changing this line.
      • This is the modern form
      • it could also be done with typedef WordCountT DataT;, but you should use the other form.
      • It could also be done with a #define BUT DO NOT DO THAT.
    • Note I declare MAX_WORDS outside of the class.
    • Note I perform most of the initialization in the declaration
      • I really don't need a constructor because of this.
      • The compiler will write one for me.
      • Which will be the default constructor, which does nothing.
  • The implementation of [] is interesting
    • There are two forms
      • One that returns a constant reference.
      • One that returns a reference.
  • The constant reference
    • This is for the right hand side (RHS).

    • WordArrayT words;
      WordCountT word;
      ...
      word = words[3]; 

    • It gives me back an array entry that I will not change.
    • The prototype is const DataT & operator [] (size_t index) const
    • You could also use the modern constexpr, but I have not yet learned that.
    • The function just returns the data at the index.
    • This is dangerous, but convention says it is the user's responsibility to get the index right.
  • The RHS at
    • Same semantics
    • But checks to see if the index is valid.
    • We have a problem here, what do we return if the index is not valid?
      • For now we will return data[0], but this is bad.
      • Later we will learn about exceptions, which is what we should do here.
  • The reference (or left hand side, LHS);

    • WordArrayT words;
      WordCountT word;
      ...
      words[3] = word; 

    • This allows us to change an element in the array.
    • The prototype is DataT & operator [] (size_t index);.
  • The LHS at function is the same.
  • Surprisingly these functions are duplicates here, but perhaps not for other structures.
• See WordArrayT.cpp.