USING: heaps.private help.markup help.syntax kernel math assocs
math.order quotations ;
IN: heaps

ARTICLE: "heaps" "Heaps"
"A heap is an implementation of a " { $emphasis "priority queue" } ", which is a structure that maintains a sorted set of elements. The key property is that insertion of an arbitrary element and removal of the first element (determined by order) is performed in O(log n) time."
$nl
"Heap elements are key/value pairs and are compared using the " { $link <=> } " generic word on the first element of the pair."
$nl
"There are two classes of heaps. Min-heaps sort their elements so that the minimum element is first:"
{ $subsections
    min-heap
    min-heap?
    <min-heap>
}
"Max-heaps sort their elements so that the maximum element is first:"
{ $subsections
    max-heap
    max-heap?
    <max-heap>
}
"Both obey a protocol."
$nl
"Queries:"
{ $subsections
    heap-empty?
    heap-size
    heap-peek
}
"Insertion:"
{ $subsections
    heap-push
    heap-push*
    heap-push-all
}
"Removal:"
{ $subsections
    heap-pop*
    heap-pop
    heap-delete
}
"Processing heaps:"
{ $subsections slurp-heap } ;

ABOUT: "heaps"

HELP: <min-heap>
{ $values { "min-heap" min-heap } }
{ $description "Create a new " { $link min-heap } "." } ;

HELP: <max-heap>
{ $values { "max-heap" max-heap } }
{ $description "Create a new " { $link max-heap } "." } ;

HELP: heap-push
{ $values { "value" object } { "key" "a comparable object" } { "heap" heap } }
{ $description "Push a pair onto a heap. The key must be comparable with all other keys by the " { $link <=> } " generic word." }
{ $side-effects "heap" } ;

HELP: heap-push*
{ $values { "value" object } { "key" "a comparable object" } { "heap" heap } { "entry" entry } }
{ $description "Push a pair onto a heap, and output an entry which may later be passed to " { $link heap-delete } "." }
{ $side-effects "heap" } ;

HELP: heap-push-all
{ $values { "assoc" assoc } { "heap" heap } }
{ $description "Push every key/value pair of an assoc onto a heap." }
{ $side-effects "heap" } ;

HELP: heap-peek
{ $values { "heap" heap } { "value" object } { "key" object } }
{ $description "Output the first element in the heap, leaving it in the heap." } ;

HELP: heap-pop*
{ $values { "heap" heap } }
{ $description "Remove the first element from the heap." }
{ $side-effects "heap" } ;

HELP: heap-pop
{ $values { "heap" heap } { "value" object } { "key" object } }
{ $description "Output and remove the first element in the heap." }
{ $side-effects "heap" } ;

HELP: heap-empty?
{ $values { "heap" heap } { "?" boolean } }
{ $description "Tests if a heap has no nodes." } ;

HELP: heap-size
{ $values { "heap" heap } { "n" integer } }
{ $description "Returns the number of key/value pairs in the heap." } ;

HELP: heap-delete
{ $values { "entry" entry } { "heap" heap } }
{ $description "Remove the specified entry from the heap." }
{ $errors "Throws an error if the entry is from another heap or if it has already been deleted." }
{ $side-effects "heap" } ;

HELP: slurp-heap
{ $values { "heap" heap } { "quot" { $quotation ( ... value key -- ... ) } } }
{ $description "Removes entries from a heap and processes them with the quotation until the heap is empty." } ;