Lecture 4

Learning objectives

After this class, you should be able to:

1. Declare a vector class and use its following features: back, begin, empty, erase, front, insert, [ ], pop_back, push_back, rbegin, rend, constructors.
2. Use STL algorithms with the vector class.
3. Explain the semantics of insertion into a vectors whose current storage is already full.
4. Use the STL string class, including performing I/O with it.

Reading assignment

1. Section 1.8.
2. Review material from discrete math, relevant to review questions on the next lecture.

Exercises and review questions

• Exercises and review questions on current lecture's material
  1. Replace erase in the file usevec.cpp with pop_back.
  2. Write a program that will take the following command line arguments: n a b. n is an integer, while a and b are floating point numbers, with a < b. The interval (a, b) is divided into n cells of equal length. Consequently, the real number x in (a, b) will fall in cell number floor[ (x-a)/(b-a) * n]. You should use an STL vector to represent the interval (a, b), with each element of the vector representing a cell. Each cell contains an STL list. Each list, in turn, contains points that fall in that cell. The points, which are floating point numbers in the interval (a, b), are read from standard input, one point per line. The program reads points until it reads EOF (end of file, typically signaled by Control-D). For each cell, it outputs, on a separate line, the cell number and the points that lie in it. You may use any STL features that you wish to. You can take a look at the sample executable: ~cop4530/fall05/CodeExamples/Lec4/cells on the CS file server. A sample input is given in the file cells.input, in the same directory. You can try running: cells 5 -2.0 8.0 < cells.input to see the output. Please do not post your solutions to this question on the discussion board. We will check your solutions during recitation.

• Questions on next lecture's material
  1. What is the contrapositive of the statement "a implies b"?
  2. Is a statement equivalent to its contrapositive?
  3. What is the converse of the statement "a implies b"?
  4. Is a statement equivalent to its converse?
  5. Prove by induction that the sum of the first n positive integers is n(n+1)/2.
  6. If ax = b, then what is logab, when a > 1, b > 0?
  7. What is log28?