Finishing Chapter 7

• There are two points we missed in chapter 7.
  • A brief discussion of arrays.
  • Smart Pointers
• We want a two dimensional game board.
• We don't want memory leaks.
• Arrays
  • P224 of the book.
  • In c arrays are pointers to memory.
  • This is why we index from 0, it is an offset from the beginning of the array.
• When you index into an array
  • The compiler does a calculation
  • DataTypeT ary[MAX_ELEMENTS]
  • ary[i]
    • This gives you access to &ary + i * size_of(DataTypeT)
• When a c style array is passed, it is always passed by pointer.
• Sort of the end.
• Two dimensional arrays
  • DataTypeT ary[MAX_ROWS][MAX_COLS];
  • Indexing ary[row][col] is equivelent to
    • ary+(row*MAX_COLS+col)*size_of(DataType)

    • int ary[3][4]
        0 1 2 3
       +--------
      0|0 1 2 3
      1|4 5 6 7
      2|8 9 A B
                    

  • A note on rows and columns
    • A reference.
    • It really doesn't matter as long as you keep them straight.
    • In C/C++ we tend to be row major, or the row comes first.
    • In Fortran they are column major, or the column comes first.
  • When passing an mulit dimension array, you must provide all but the last dimension in the parameter type .
  • But is it customary to provide all of them.
• Multidimensional arrays with vectors.
  • The syntax gets messy, especially HTML coded c++
  • Let's just look at vectorBoard.cpp