HP Integrity NonStop H-Series - Manual (Page 147)

"prise".
The second half of example 2 illustrates the use of the copy_backward() algorithm. This function
performs the same task as the copy() algorithm, but moves elements from the end of the sequence
first, progressing to the front of the sequence. (If you think of the argument as a string, characters
are moved starting from the right and progressing to the left.) In this case the result will be that
buffer will be assigned the value "priprise". The first three characters are then modified by another
copy() operation to the values "sur", resulting in buffer holding the value "surprise".
copy_backwards
Example 3 illustrates copy() being used to move values to an output stream. (See Chapter 2: Stream
Iterators ). The target in this case is an ostream_iterator generated for the output stream cout. A
similar mechanism can be used for input values. For example, a simple mechanism to copy every
word in the input stream into a list is the following call on copy():
list words;
istream_iterator in_stream(cin), eof;
copy(in_stream, eof, inserter(words, words.begin()));
This technique is used in the spell checking program described in Chapter 8 ( Example Program - A
Spelling... ) .
Copy can also be used to convert from one type of stream to another. For example, the call in
example 4 of the sample program copies the characters held in the buffer one by one into a list of
characters. The call on inserter() creates an insert iterator, used to insert values into the list. The first
call on copy() places the string surprise, created in example 2, into the list. The second call on
copy() inserts the values from the string "big " onto the front of the list, resulting in the list
containing the characters big surprise. The final call on copy() illustrates the reverse process,
copying characters from a list back into a character buffer.
Initialize a Sequence with Generated Values
A generator is a function that will return a series of values on successive invocations. Probably the
generator you are most familiar with is a random number generator. However, generators can be
constructed for a variety of different purposes, including initializing sequences.
Like fill() and fill_n(), the algorithms generate() and generate_n() are used to initialize or reinitialize
a sequence. However, instead of a fixed argument, these algorithms draw their values from a
generator. The declarations of these algorithms are as follows:
void generate (ForwardIterator, ForwardIterator, Generator);
void generate_n (OutputIterator, Size, Generator);
Our example program shows several uses of the generate algorithm to initialize a sequence.
string generateLabel () {
// generate a unique label string of the form L_ddd
static int lastLabel = 0;