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| <TITLE>accumulate()</TITLE> |
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| <H2>accumulate()</H2> |
| <P><B>Library:</B> <A HREF="2-10.html">Numerics</A></P> |
| |
| <PRE><HR><B><I>Function</I></B><HR></PRE> |
| |
| <UL> |
| <LI><A HREF="#sec1">Local Index</A></LI> |
| <LI><A HREF="#sec2">Summary</A></LI> |
| <LI><A HREF="#sec3">Synopsis</A></LI> |
| <LI><A HREF="#sec4">Description</A></LI> |
| <LI><A HREF="#sec5">Complexity</A></LI> |
| <LI><A HREF="#sec6">Example</A></LI> |
| <LI><A HREF="#sec7">Standards Conformance</A></LI> |
| </UL> |
| <A NAME="sec1"><H3>Local Index</H3></A> |
| No Entries |
| <A NAME="sec2"><H3>Summary</H3></A> |
| <P>A generalized numeric operation that accumulates all elements within a range into a single value</P> |
| <A NAME="sec3"><H3>Synopsis</H3></A> |
| |
| <PRE>#include <numeric> |
| |
| namespace std { |
| template <class InputIterator, class T> |
| T accumulate(InputIterator start, |
| InputIterator finish, |
| T init); |
| |
| template <class InputIterator, |
| class T, |
| class BinaryOperation> |
| T accumulate(InputIterator start, |
| InputIterator finish, |
| T init, |
| BinaryOperation binary_op); |
| } |
| </PRE> |
| <A NAME="sec4"><H3>Description</H3></A> |
| <P><SAMP>accumulate()</SAMP> applies a binary operation to <SAMP>init</SAMP> and each value in the range <SAMP>[start,finish)</SAMP>. The result of each operation is returned in <SAMP>init</SAMP>. This process aggregates the result of performing the operation on every element of the sequence into a single value.</P> |
| <P>The accumulator <SAMP>acc</SAMP> is initialized with the value <SAMP>init </SAMP>and modified with <SAMP>acc = acc + *i</SAMP> or <SAMP>acc = binary_op(acc, *i)</SAMP> for each interator <SAMP>i</SAMP>, in order, in the range <SAMP>[start, finish)</SAMP>.</P> |
| <A NAME="sec5"><H3>Complexity</H3></A> |
| <P><SAMP>accumulate()</SAMP> performs exactly <SAMP>finish-start</SAMP> applications of the binary operation, <SAMP>operator+ </SAMP>by default.</P> |
| <A NAME="sec6"><H3>Example</H3></A> |
| |
| <UL><PRE>// |
| // accum.cpp |
| // |
| |
| #include <numeric> // for accumulate |
| #include <vector> // for vector |
| #include <functional> // for multiplies |
| #include <iostream> // for cout |
| |
| |
| int main () |
| { |
| // Typedef for convenience. |
| typedef std::vector<int, std::allocator<int> > vector; |
| |
| // Initialize a vector using an array of integers. |
| const vector::value_type arr[] = |
| { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 }; |
| vector v1 (arr, arr + sizeof arr / sizeof *arr); |
| |
| // Accumulate sums and products. |
| vector::value_type sum = |
| std::accumulate (v1.begin (), v1.end (), 0); |
| |
| vector::value_type prod = |
| std::accumulate (v1.begin (), v1.end (), 1, |
| std::multiplies<vector::value_type>()); |
| |
| // Output the results. |
| std::cout << "For the series: "; |
| for (vector::iterator i = v1.begin (); i != v1.end (); ++i) |
| std::cout << *i << " "; |
| |
| std::cout << "where N = " << v1.size () |
| << "\nThe sum = (N * N + N) / 2 = " << sum |
| << "\nThe product = N! = " << prod << std::endl; |
| |
| return 0; |
| } |
| |
| |
| Program Output: |
| |
| For the series: 1 2 3 4 5 6 7 8 9 10 where N = 10 |
| The sum = (N * N + N) / 2 = 55 |
| The product = N! = 3628800 |
| </PRE></UL> |
| <UL><PRE></PRE></UL> |
| <A NAME="sec7"><H3>Standards Conformance</H3></A> |
| <P><I>ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 26.4.1</I></P> |
| |
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