# Strings and Classes

Welcome to PB161. If you haven't read the rules and guidelines in
Part A (directory ‹00› in the source bundle), please do so now,
before going on.

The exercises today will look at some of the basics that you have
seen in the lecture: strings, dynamic arrays – ‹std::vector›,
classes with methods and ‹const› references. These concepts are
further explored in the ‘demonstrations’ (commented examples; please
note that these do not replace the lectures, but are rather
complementary to it). The corresponding files in the source bundle
are named ‹d?_*.cpp›, i.e. ‹d1_fibonacci.cpp› through ‹d4_???.cpp›.

 1. ‹fibonacci› – using ‹std::vector› (dynamic array)
 2. ‹hamming›   – introduction to ‹std::string›
 3. ‹hero›      – introduction to object composition
 4. ‹lemmings›  – collections of custom objects

The second part of the study materials for each week gives you a
couple of ‘elementary’ exercises, which you should be able to
quickly solve to make sure you understand the concepts from the
lecture and from the commented examples above. Sample solutions are
in Part S at the end of the PDF, or in the directory ‹sol› in the
source code bundle. Please note that the sample solution is not
always the simplest possible – it's fine to take a more roundabout
approach. The source files for this section are named ‹e?_*.cpp›.

This week, the elementary exercises are:

 1. ‹predicates› – properties of lists of numbers
 2. ‹palindrome› – checking that an ‹std::string› is a palindrome
 3. ‹pascal›     – fill in an ‹std::vector›

The next section has more difficult exercises, suitable to practice
programming with the concepts that you have learned this week.
Solutions to these can be freely discussed and shared, you can work
on the exercises with your friends, and you can compare your
solution to the one included in Part S. The files are named
‹f?_*.cpp›.

 1. ‹wrap›    – wrap long lines into paragraphs of a given width
 2. ‹digits›  – representing numbers in a positional system
 3. ‹sieve›   – find prime numbers
 4. ‹bsearch› – binary search in a sorted ‹std::vector›

The last section are ‘graded’ exercises, in the sense that you will
have to solve and submit 9 of those in each block. The respective
source files in the bundle are called ‹g?_*.cpp›. Discussing and
sharing solutions is strictly forbidden – you must solve the
exercises on your own. For details, see Part A (directory ‹00› in
the source bundle).

 1. ‹counting› – count words and lines in a string
 2. ‹fraction› – evaluate a continued fraction
 3. ‹words›    – break a string into a vector of one-word strings
 4. ‹account›  – encapsulation of state, ‹const› methods
 5. ‹shapes›   – object composition
 6. ‹contacts› – collections of your own objects

## a. Using the source bundle

We recommend that you work on ‹aisa›, which has all the required
tools installed and set up correctly. You can use ‹micro› as your
editor if you are not familiar with ‹vim›, or you can use a remote
editing feature in your code editor of choice. If you prefer to set
up your own, local, environment, you are of course free to do that,
but please keep in mind that your tools are your responsibility.

If you work on ‹aisa›, you can check your solutions against the test
cases provided with the exercises by running ‹make check›:

    $ make check
    e1_predicates    ok
    e2_palindrome    ok
    e3_pascal        ok
    f1_wrap          ok
    f2_digits        fail
      assertion "digits( 1337, 10 ) == d10_1337" failed […]
    f3_sieve         no build
    f4_bsearch       no build
    g1_counting      ok
    g3_words         no build
    g4_account       no build
    g5_shapes        no build
    g6_contacts      no build