Generic Programming Techniques in C

1
Generic Programming Techniques in C

• Generic programming allows diverse types to be
  used together
• Without requiring inheritance relations among
  them
• Lets native, library, and user-defined types work
  with each other well
• Generic abstractions rely on interface
  polymorphism
• Based on C templates, typedefs, and compilers
  type inference rules
• Allow many combinations to be composed
  successfully
• Impose specific rules on types interfaces
• Today well look at some examples for why this is
  useful
• To motivate investment of effort towards a deeper
  understanding
• To show some early techniques that you can apply
  right away
• Subsequent lectures and studios will dig into
  this in more detail
• Well look first at key generic abstractions the
  STL provides
• Containers that can hold diverse types
• Iterators that define ranges, act like built-in
  pointer types
• Algorithms that use iterators to manipulate data
  in containers
• Function objects that are used to extend
  containers and algorithms

2
STL Containers Can Hold Different Types

• include ltvectorgt
• include ltiostreamgt
• using namespace std
• int main (int, char )
• vectorltchar gt cstrings
• vectorltintgt numbers
• cstrings.push_back(one)
• cstrings.push_back(two)
• numbers.push_back(1)
• numbers.push_back(2)
• cout ltlt cstrings0 ltlt endl ltlt cstrings1 ltlt
  endl
• ltlt numbers0 ltlt endl ltlt numbers1 ltlt
  endl
• return 0 // what output is produced, and why?

3
STL Iterators Can Act Like Pointers (Somewhat)

• include ltvectorgt
• include ltiostreamgt
• using namespace std
• int main (int, char )
• vectorltchar gt cstrings
• vectorltintgt numbers
• cstrings.push_back(one) cstrings.push_back(t
  wo)
• numbers.push_back(1) numbers.push_back(2)
• vectorltchar gtiterator cstrings_iter
  
  
• cstrings.begin()
  
  
• vectorltintgtiterator numbers_iter
  numbers.begin()
  
• cout ltlt cstrings_iter ltlt endl
  
  
• cstrings_iter
  
  
• cout ltlt cstrings_iter ltlt endl
  
  
• cout ltlt numbers_iter ltlt endl
  
  
• numbers_iter
  
  
• cout ltlt numbers_iter ltlt endl
• return 0 // what output is produced, and why?

4
STL Algorithms Use Iterators to Manipulate Data

• include ltvectorgt
• include ltiostreamgt
• include ltalgorithmgt
• include ltiteratorgt
• using namespace std
• int main (int, char )
• vectorltchar gt cstrings
• vectorltintgt numbers
• cstrings.push_back(one)
• cstrings.push_back(two)
• numbers.push_back(1)
• numbers.push_back(2)
• copy (cstrings.begin(), cstrings.end(),
• ostream_iteratorltchar gt(cout, \n))
• copy (numbers.begin(), numbers.end(),
• ostream_iteratorltintgt(cout, \n))
• return 0 // what output is produced, and why?

5
STL Functors Extend Algorithms ( Containers)

• include ltvectorgt
• include ltiostreamgt
• include ltalgorithmgt
• include ltiteratorgt
• using namespace std
• int main (int, char )
• vectorltchar gt cstrings
• cstrings.push_back(one)
• cstrings.push_back(two)
• sort (cstrings.begin(), cstrings.end(),
• greaterltchar gt())
• copy (cstrings.begin(), cstrings.end(),
• ostream_iteratorltchar gt(cout, \n))
• return 0 // what output is produced, and why?