Standard Template Library (STL)

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Standard Template Library (STL)

• Overview Part 1
• Yngvi Bjornsson

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STL

• Collection of useful
• abstract data types (ADT)
• generic algorithms
• Implemented as class / function templates
• STL is
• not a part of the C language itself
• but a part of the C standard!

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STL Components

• Six main components
• Containers
• Sequence
• Associative
• Iterators
• Constant/Mutable
• Forward/Bi-directional/Random Access
• Adaptors
• Container / Interator / Function
• Allocators
• Generic algorithms
• Function objects

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Containers

• Sequence Containers
• Arrange data-items into a linear arrangement.
• Container types
• vectorltTgt
• dequeltTgt
• listltTgt
• (Sorted) Associative Containers
• Fast insert/retrieval of data-items based on keys
• Container types
• setltKeygt multisetltKeygt
• mapltKey,Tgt multimapltKey,Tgt
• "multi" containers allow multiple items with same
  key.

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Sequence Containers

• Vector
• Efficient add/delete back, access/modify any
  element
• Deque
• Efficient add/delete front/back, access/modify
  any element
• List
• Efficient add/del. elements anywhere, access/mod.
  front/back

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Common Operations on Seq. Containers
Descr. Method V D L Descr. Method V D L
E front (ref) front Del all clear
E back (ref) back Add pos insert ? ?
Add E back push_back Del pos erase ? ?
Del E back pop_back lt
Add E front push_front - !
Del E front pop_front -
E at subscript - E size
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include ltlistgt include ltvectorgt include
ltdequegt using namespace std int main() //
STL Vector can use as an array (grows
dynamically!) vectorltintgt V1(10), V2 for (
int i0 ilt10 i ) V1i i //
NOTE cannot use subscript unless element
exists! V2.push_back(i) for ( int
i0 ilt10 i ) cout ltlt V1i ltlt " " ltlt V2i
ltlt endl // STL Deque dequeltintgt D1, D2
for ( int i0 ilt10 i ) D1i i
D2.push_front(i) for ( int i0 ilt10 i
) cout ltlt D1i ltlt " " ltlt D2i ltlt endl //
STL List (no subscripting) listltintgt L1, L2
for ( int i0 ilt10 i )
L1.push_back(i) L2.push_front(i) for (
int i0 ilt10 i ) cout ltlt L1.front()
ltlt " " ltlt L2.back() ltlt endl
L1.pop_front() L2.pop_back()
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Iterators

• Standard interface of how to traverse elements in
  a container.
• Allows us to write generic algorithms that work
  for any container! ( almost)
• Iterators behave in a way like pointers
• (dereference), , --, , !, , -
• Can think of as generalized pointers

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Iterators and Containers

• The container classes have methods
• begin() Returns an iterator "pointing" to first
  element
• end() Returns an iterator pointing after last
  element
• (also rbegin() and rend() for reverse traversal)
• Example
• // Displays element of list Llistltintgtiterator
  ilfor ( ilL.begin() il ! L.end() il )
  cout ltlt il ltlt endl

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Iterator Kind

• Kind
• Forward iterators
• , !, , (dereference)
• Bi-directional iterators
• -- (additially to forward iterators)
• Random access iterators
• , , -, , - (additionally to bi-directional
  iterators)
• Containers
• List (bi-directional), vector and deque
  (random-access)

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Iterator Declaration

• Mutable (default)
• listltintgtiterator
• Constant
• Listltintgtconst_iterator
• Reverse (also mutable)
• listltintgtreverse_iterator
• Constant and Reverse
• listltintgtconst_reverse_iterator

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Generic Algorithm

• templatelttypename IterType, typename ElemTypegt
• IterType find(IterType first, IterType last,
  const elemType value)
• for ( first ! last first)
• if (value first)
• return first
• return last
• vectorltintgt ivec
• vectorltintgtiterator it find(ivec.begin(),
  ivec.end(), 1024)
• if (it!ivec.end()) // found 1024 in ivec
• listltstringgt slist
• listltintgtiterator iter find(slist.begin(),
  slist.end(), "duck")
• if (iter!slist.end()) // found "duck in
  slist

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Container Adaptors

• Container classes implemented on top of the
  existing containers (adapt their interface)
• stack (default container deque)
• queue (default container deque)
• priority_queue (default container vector)
• Can change underlying container class
• stackltint, vectorltintgt gt
• Note, need space in between gt

Why?
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Operations on Adapter Containers
Descr. Method S Q P
of elements (E) size
is empty? empty
E at top (ref) top -
Add E top / back push
Del E top / front pop
E at front (ref) front - -
E at back (ref) back - -
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include ltstackgt include ltqueuegt using namespace
std int main() // STL Stack stackltint,
vectorltintgt gt S // Changing default container
(note 'gt gt', not 'gtgt') for ( int i0 ilt10
i ) S.push(i) for ( int i0 ilt10 i )
cout ltlt S.top() ltlt " " S.top() 2
S.top() cout ltlt S.top() ltlt endl
S.pop() // STL Queue queueltintgt Q
for ( int i0 ilt10 i ) Q.push(i) for (
int i0 ilt10 i ) cout ltlt Q.front() ltlt
endl Q.pop() // STL Priority Queue
priority_queueltintgt P for ( int i0 ilt10
i ) P.push(i) for ( int i0 ilt10 i )
cout ltlt P.top() ltlt endl P.pop()
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Associative Containers

• set
• Add/Delete elements to/from set (no duplications)
  
• Can ask of membership (is in set)
• map (associative array)
• Add/Delete pairs to/from map (no duplications of
  keys)
• multiset / multimap essentially the same except
  duplications of keys allowed.

a
b
c
d
a
1
b
2
c
1
d
0
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Common Operations on Associative Containers
Descr. Method S M
of elements (E) size
is empty? empty
Add element insert
Delete element erase
Find element (ref) find
The same
Subscript with key
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include ltstringgt include ltsetgt include
ltmapgt using namespace std int main() // STL
set setltstringgt S S.insert("hi")
S.insert("how") S.insert("are")
S.insert("you") for ( setltstringgtiterator
isS.begin() is ! S.end() is ) cout
ltlt is ltlt endl // STL map
mapltstring,intgt M M"Hi" 0 M"how"
1 M"are" 2 M"you" 1 if (
M.find("how") ! M.end() ) cout ltlt "'how'
is in map" ltlt endl for ( mapltstring,intgtitera
tor imM.begin() im!M.end() im )
cout ltlt im-gtfirst ltlt " " ltlt im-gtsecond ltlt endl
// note use of pair
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Summary

• Overview of STL
• Containers
• Iterators
• Some of the containers have
• additional methods not covered here
• e.g. can splice lists
• For complete documentation (and intro)
• http//www.sgi.com/tech/stl/