Chapter 1 C Templates

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Chapter 1C Templates
Sections 1.6 and 1.7
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Templates

• Type-independent patterns that can work with
  multiple data types
• Generic programming
• Code reusable
• Function Templates
• These define logic behind the algorithms that
  work for multiple data types
• Class Templates
• These define generic class patterns into which
  specific data types can be plugged in to produce
  new classes

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Function Templates

• Algorithms may use the same logic for different
  data types
• Different definitions are written just to deal
  with different data types
• Templates permit a common code, independent of
  the data type
• Templates should be in header files, so that the
  compiler will know how to generate code when it
  sees the template used
• Examples
• Lec4/largest.h/cpp, uselargest.cpp

Error with template in the .cpp file g
uselargest.cpp largest.cpp /tmp/ccAg3qmY.o In
function main' uselargest.cpp(.text0x133)
undefined reference to int tlargestltintgt(int,
int)' uselargest.cpp(.text0x16c) undefined
reference to float tlargestltfloatgt(float, int)'
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Class Templates

• Identical code can be used for classes that have
  data of different types
• Examples
• Lec4/pair.h, usepair.cpp
• Use friend function to access private members
  (example, for IO)
• The approach used in the text is also ok
• Note the use of a space between gt and gt in
  usepair.cpp
• This makes the compiler realize that gtgt is not a
  single token

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An Alternative to friend

• Use a public print function and an operator
  that calls it

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STL Containers

• Container stores other objects
• Common operations such as push_back, back,
  front, , etc
• Not all operations are defined for all containers
• Sequence positions of elements are important
• Example vector, list
• Associative containers elements are accessed
  through keys
• Example map, set, pair
• Example
• Lec4/vlm.cpp for example with vector, list, and
  map

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STL Iterators

• Iterator like a pointer to elements of a
  container
• Used to access elements of a container
• Popular operators
• (dereference), , --, , !
• Examining all the elements of a container
• c.begin() returns an iterator to the first
  element of container c
• c.end returns a pointer to one past the end

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Matrices

• C library does not provide a matrix class
• Constructor
• Creates rows number of zero-sized vectors
• Resizes each vector to col elements
• Two types of operators
• One for LHS that returns by reference
• Another for RHS that returns by constant
  reference
• toi fromi
• So we have two very identical functions
• What makes their signatures different?