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| 129 | .\" ======================================================================== |
| 130 | .\" |
| 131 | .IX Title "Heap 3" |
| 132 | .TH Heap 3 "2003-12-04" "perl v5.8.0" "User Contributed Perl Documentation" |
| 133 | .SH "NAME" |
| 134 | Heap \- Perl extensions for keeping data partially sorted |
| 135 | .SH "SYNOPSIS" |
| 136 | .IX Header "SYNOPSIS" |
| 137 | .Vb 1 |
| 138 | \& use Heap; |
| 139 | .Ve |
| 140 | .PP |
| 141 | .Vb 2 |
| 142 | \& my $heap = Heap->new; |
| 143 | \& my $elem; |
| 144 | .Ve |
| 145 | .PP |
| 146 | .Vb 1 |
| 147 | \& use Heap::Elem::Num(NumElem); |
| 148 | .Ve |
| 149 | .PP |
| 150 | .Vb 4 |
| 151 | \& foreach $i ( 1..100 ) { |
| 152 | \& $elem = NumElem( $i ); |
| 153 | \& $heap->add( $elem ); |
| 154 | \& } |
| 155 | .Ve |
| 156 | .PP |
| 157 | .Vb 3 |
| 158 | \& while( defined( $elem = $heap->extract_maximum ) ) { |
| 159 | \& print "Smallest is ", $elem->val, "\en"; |
| 160 | \& } |
| 161 | .Ve |
| 162 | .SH "DESCRIPTION" |
| 163 | .IX Header "DESCRIPTION" |
| 164 | The Heap collection of modules provide routines that manage |
| 165 | a heap of elements. A heap is a partially sorted structure |
| 166 | that is always able to easily extract the smallest of the |
| 167 | elements in the structure (or the largest if a reversed compare |
| 168 | routine is provided). |
| 169 | .PP |
| 170 | If the collection of elements is changing dynamically, the |
| 171 | heap has less overhead than keeping the collection fully |
| 172 | sorted. |
| 173 | .PP |
| 174 | The elements must be objects as described in \*(L"Heap::Elem\*(R" |
| 175 | and all elements inserted into one heap must be mutually |
| 176 | compatible \- either the same class exactly or else classes that |
| 177 | differ only in ways unrelated to the \fBHeap::Elem\fR interface. |
| 178 | .SH "METHODS" |
| 179 | .IX Header "METHODS" |
| 180 | .ie n .IP "$heap = \fIHeapClass::new()\fR; $heap2\fR = \f(CW$heap1\fR\->\fInew();" 4 |
| 181 | .el .IP "$heap = \fIHeapClass::new()\fR; \f(CW$heap2\fR = \f(CW$heap1\fR\->\fInew()\fR;" 4 |
| 182 | .IX Item "$heap = HeapClass::new(); $heap2 = $heap1->new();" |
| 183 | Returns a new heap object of the specified (sub\-)class. |
| 184 | This is often used as a subroutine instead of a method, |
| 185 | of course. |
| 186 | .IP "$heap\->\s-1DESTROY\s0" 4 |
| 187 | .IX Item "$heap->DESTROY" |
| 188 | Ensures that no internal circular data references remain. |
| 189 | Some variants of Heap ignore this (they have no such references). |
| 190 | Heap users normally need not worry about it, \s-1DESTROY\s0 is automatically |
| 191 | invoked when the heap reference goes out of scope. |
| 192 | .IP "$heap\->add($elem)" 4 |
| 193 | .IX Item "$heap->add($elem)" |
| 194 | Add an element to the heap. |
| 195 | .ie n .IP "$elem = $heap\->top" 4 |
| 196 | .el .IP "$elem = \f(CW$heap\fR\->top" 4 |
| 197 | .IX Item "$elem = $heap->top" |
| 198 | Return the top element on the heap. It is \fBnot\fR removed from |
| 199 | the heap but will remain at the top. It will be the smallest |
| 200 | element on the heap (unless a reversed cmp function is being |
| 201 | used, in which case it will be the largest). Returns \fIundef\fR |
| 202 | if the heap is empty. |
| 203 | .Sp |
| 204 | This method used to be called \*(L"minimum\*(R" instead of \*(L"top\*(R". The |
| 205 | old name is still supported but is deprecated. (It was confusing |
| 206 | to use the method \*(L"minimum\*(R" to get the maximum value on the heap |
| 207 | when a reversed cmp function was used for ordering elements.) |
| 208 | .ie n .IP "$elem = $heap\->extract_top" 4 |
| 209 | .el .IP "$elem = \f(CW$heap\fR\->extract_top" 4 |
| 210 | .IX Item "$elem = $heap->extract_top" |
| 211 | Delete the top element from the heap and return it. Returns |
| 212 | \&\fIundef\fR if the heap was empty. |
| 213 | .Sp |
| 214 | This method used to be called \*(L"extract_minimum\*(R" instead of |
| 215 | \&\*(L"extract_top\*(R". The old name is still supported but is deprecated. |
| 216 | (It was confusing to use the method \*(L"extract_minimum\*(R" to get the |
| 217 | maximum value on the heap when a reversed cmp function was used |
| 218 | for ordering elements.) |
| 219 | .IP "$heap1\->absorb($heap2)" 4 |
| 220 | .IX Item "$heap1->absorb($heap2)" |
| 221 | Merge all of the elements from \fI$heap2\fR into \fI$heap1\fR. |
| 222 | This will leave \fI$heap2\fR empty. |
| 223 | .IP "$heap1\->decrease_key($elem)" 4 |
| 224 | .IX Item "$heap1->decrease_key($elem)" |
| 225 | The element will be moved closed to the top of the |
| 226 | heap if it is now smaller than any higher parent elements. |
| 227 | The user must have changed the value of \fI$elem\fR before |
| 228 | \&\fIdecrease_key\fR is called. Only a decrease is permitted. |
| 229 | (This is a decrease according to the \fIcmp\fR function \- if it |
| 230 | is a reversed order comparison, then you are only permitted |
| 231 | to increase the value of the element. To be pedantic, you |
| 232 | may only use \fIdecrease_key\fR if |
| 233 | \&\fI$elem\-\fRcmp($elem_original) <= 0> if \fI$elem_original\fR were |
| 234 | an elem with the value that \fI$elem\fR had before it was |
| 235 | \&\fIdecreased\fR.) |
| 236 | .ie n .IP "$elem = $heap\->delete($elem)" 4 |
| 237 | .el .IP "$elem = \f(CW$heap\fR\->delete($elem)" 4 |
| 238 | .IX Item "$elem = $heap->delete($elem)" |
| 239 | The element is removed from the heap (whether it is at |
| 240 | the top or not). |
| 241 | .SH "AUTHOR" |
| 242 | .IX Header "AUTHOR" |
| 243 | John Macdonald, jmm@perlwolf.com |
| 244 | .SH "COPYRIGHT" |
| 245 | .IX Header "COPYRIGHT" |
| 246 | Copyright 1998\-2003, O'Reilly & Associates. |
| 247 | .PP |
| 248 | This code is distributed under the same copyright terms as perl itself. |
| 249 | .SH "SEE ALSO" |
| 250 | .IX Header "SEE ALSO" |
| 251 | \&\fIHeap::Elem\fR\|(3), \fIHeap::Binary\fR\|(3), \fIHeap::Binomial\fR\|(3), \fIHeap::Fibonacci\fR\|(3). |