Programming Using the C Standard Template Library

1
Programming Using the C Standard Template
Library

• Tim Smith
• October 13, 2004

2
What is the STL?

• A collection of classes to make C programming
  more efficient
• Algorithms, Containers, and Iterators
• Function objects, Allocators, and Adapters

Function Objects
Allocators
Iterators
Containers
Algorithms
Adapters
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STL Containers

• Sequences
• Vector
• Bit_vector
• Deque
• List
• Slist

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STL Containers

• Associative Containers
• Set
• Multiset
• Map
• Multimap
• Hash_set
• Hash_map
• Not part of the C Standard

5
Creating Containers

• includeltvectorgt
• includeltlistgt
• includeltmapgt
• using namespace std
• int main()
• vectorltintgt v1 //empty vector of
  integers
• vectorltintgt v2(100) //vector of 100
  integers.
• //initialized using
  default integer constructor.
• vectorltintgt v3(100,5) //vector of 100
  integers all initialized to 5.
• listltdoublegt l1 //empty list of
  doubles.
• listltdoublegt l2(100) //list of 100
  doubles.
• //initialized with
  default constructor.
• listltdoublegt l3(100,3.14) //list of 100
  doubles all initialized to 3.14.
• mapltint,doublegt m1 //empty map that
  associates integers with doubles

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Inserting and Deleting Elements

• includeltvectorgt
• includeltlistgt
• includeltmapgt
• using namespace std
• int main()
• vectorltintgt v1 //empty vector of
  integers
• listltdoublegt l1 //empty list of
  doubles.
• mapltint,doublegt m1 //empty map that
  associates integers with doubles
• int x 3
• double y 3.14
• v1.push_back(x) //insert a copy of x
  at end of vector
• v1.insert(v1.begin(),x) //insert a copy of x
  before the first element
• l1.push_back(y) //insert a copy of y
  at end of list
• l1.push_front(y) //insert a copy of y
  at front of list

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Accessing Elements in Containers

• Access to an element stored in a container is
  done through STL iterators most of the time
• An iterator is an abstraction that provides data
  access operations needed by algorithms (read,
  write, next element, prev element, etc.)
• STL has several different iterator types

Input
Forward
Bidirectional
Random Access
Output
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STL Iterators

• Used as arguments to algorithms
• Containers provide several iterators
• Begin, End, Reverse Begin, Reverse End

Input Operations , , !, , -gt, , No
assignment of i
Output Operations , ,
Forward Operations , , !, , -gt,
Bidirectional Operations , , !, , -gt, , --
Random Operations , , !, , -, , -gt, ,
, -, --, n, lt, lt, gt, gt
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Iterator Operations

• Input
• (read), (next element)
• Output
• (write), (next element)
• Forward
• (read/write), (next element)
• Bidirectional
• (read/write), (next element), --
  (previous element)
• Random Access
• (read/write), /-- (next/prev element),
  (next nth element), - (previous nth element)

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Iterator Operations Example

• includeltvectorgt
• includeltlistgt
• using namespace std
• int main()
• listltintgt l(10)
• vectorltintgt v(10)
• listltintgtiterator i l.begin()
• i i i-- --i
• int x i
• i 7
• vectorltintgtiterator j v.begin()
• j j j-- --j
• j 5 j - 5
• int y j

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Iterating Through a Container

• Containers all provide begin() and end()
• begin() returns iterator pointing to first
  element
• end() returns iterator pointing one past the last
  element
• rbegin() and rend() provide to iterate through
  container from end to beginning
• use containerlttypegtreverse_iterator

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Iterate Through Container

• include ltiostreamgt
• include ltvectorgt
• using namespace std
• int main()
• vectorltintgt v(10,7)
• for (vectorltintgtiterator i v.begin()
• i ! v.end()
• i)
• cout ltlt i ltlt " "
• cout ltlt endl

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STL Algorithms

• Each algorithm examined to identify data access
  operations used.
• Algorithms written using the appropriate STL
  iterator.
• Allows one algorithm to work on multiple types of
  containers that provide the appropriate iterator
  type.
• Most algorithms work with Forward Iterators.

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STL Algorithms

• 4 categories of algorithms
• Non-modifying For each, Find, Count, Equal,
  Search, etc.
• Mutating Copy, Generate, Reverse, Remove, Swap,
  etc.
• Sorting Related Sort, Stable sort, Binary
  search, Merge, etc.
• Numeric Accumulate, Inner product, Partial
  sum, Adjacent difference

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Sort Elements in a Vector

• includeltiostreamgt
• includeltvectorgt
• includeltalgorithmgt
• using namespace std
• int main()
• vectorltintgt v
• for (int i 0 i lt 10 i 2)
• v.push_back(i)
• for (int i 1 i lt 10 i 2)
• v.push_back(i)
• for (vectorltintgtiterator i v.begin() i !
  v.end() i)
• cout ltlt i ltlt " "
• cout ltlt endl
• sort(v.begin(), v.end())

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Function Objects

• Used by some algorithms
• Applied to each element in input by For each
• Used to create new elements by Generate
• Predicates - Function Objects that return bool
• Unary and Binary predicates used to test equality
• Find If uses unary, Sort uses binary

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Example Function Objects

• class generator
• private
• int counter
• public
• generator() counter(0)
• int operator()()
• return counter
• class printer
• public
• int operator()(int val)
• cout ltlt val ltlt " "

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• int main()
• vectorltintgt v(10)
• generator gen
• printer prn
• for_each(v.begin(), v.end(), prn) //Print the
  uninitialized vector
• cout ltlt endl
• generate(v.begin(), v.end(), gen)
  //Initialize the vector
• for_each(v.begin(), v.end(), prn) //Print the
  vector again
• cout ltlt endl

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Predicate Object Example

• includeltiostreamgt
• includeltlistgt
• includeltalgorithmgt
• includeltfunctionalgt
• using namespace std
• struct is_zero public unary_functionltint, boolgt
  
• bool operator()(int x) return x 0
• int main()
• listltintgt l
• l.push_back(-1) l.push_back(0)
  l.push_back(1) l.push_back(-3)
• listltintgtiterator result find_if(l.begin(),
  l.end(),
• 
  bind2nd(greaterltintgt(), 0))
• if (result ! l.end())
• cout ltlt result ltlt endl

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STL Summary

• STL allows programmers to focus on application
  specific issues
• Provides collections of algorithms, containers,
  iterators, and other objects
• Programmers dont reinvent the wheel

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STL Resources

• http//www.sgi.com/tech/stl/ SGIs STL reference
  documentation
• Musser, Derge, Saini. STL Tutorial and Reference
  Guide. C Programming with the Standard Template
  Library, 2nd Edition. Addison-Wesley, 2001.
• Josuttis.The C Standard Library A Tutorial and
  Reference. Addison-Wesley, 1999.
• Stroustrup. The C Programming Language, 3rd
  Edition. Addison-Wesley, 1997.