syntax: 'meth' -> 'fun', 'attr' -> 'var'

[nit.git] / lib / standard / abstract_collection.nit

# This file is part of NIT ( http://www.nitlanguage.org ).
#
# Copyright 2004-2008 Jean Privat <jean@pryen.org>
#
# This file is free software, which comes along with NIT.  This software is
# distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
# without  even  the implied warranty of  MERCHANTABILITY or  FITNESS FOR A 
# PARTICULAR PURPOSE.  You can modify it is you want,  provided this header
# is kept unaltered, and a notification of the changes is added.
# You  are  allowed  to  redistribute it and sell it, alone or is a part of
# another product.

# This module define several abtract collection classes.
package abstract_collection

import kernel

# The root of the collection hierarchy.
#
# Instances of this class offers an iterator method.
#
# Colections instances can use the "for" structure:
#         var x: Collection[U]
#         ...
#         for u in x do
#             # u is a U
#             ...
#         end
# that is equivalent with
#         var x: Collection[U]
#         ...
#         var i = x.iterator
#         while i.is_ok do
#             var u = i.item # u is a U
#             ...
#             i.next
#         end
#
# This abstract class implements its others methods with an iterator.
# Subclasses may redefine them with an efficient implementation.
interface Collection[E]
        # Get a new iterator on the collection.
        fun iterator: Iterator[E] is abstract

        # Is there no item in the collection ?
        fun is_empty: Bool is abstract 

        # Number of items in the collection.
        fun length: Int is abstract

        # Is `item' in the collection ?
        # Comparaisons are done with ==
        fun has(item: E): Bool is abstract

        # Is the collection contain only `item' ?
        # Comparaisons are done with ==
        # Return true if the collection is empty.
        fun has_only(item: E): Bool is abstract

        # How many occurences of `item' are in the collection ?
        # Comparaisons are done with ==
        fun count(item: E): Int is abstract

        # Return one the item of the collection
        fun first: E is abstract
end

# Naive implementation of collections method
# You only have to define iterator!
interface NaiveCollection[E]
special Collection[E]
        redef fun is_empty do return length == 0

        redef fun length
        do
                var nb = 0
                for i in self do nb += nb
                return nb
        end

        redef fun has(item)
        do
                for i in self do if i == item then return true
                return false
        end

        redef fun has_only(item)
        do
                for i in self do if i != item then return false
                return true
        end

        redef fun count(item)
        do
                var nb = 0
                for i in self do if i == item then nb += 1
                return nb
        end

        redef fun first
        do
                assert length > 0
                return iterator.item
        end
end

# Instances of the Iterator class generates a series of elements, one at a time.
# They are mainly used with collections.
interface Iterator[E]
        # The current item.
        # Require `is_ok'.
        fun item: E is abstract

        # Jump to the next item.
        # Require `is_ok'.
        fun next is abstract

        # Is there a current item ?
        fun is_ok: Bool is abstract
end

# A collection that contains only one item.
class Container[E]
special Collection[E]

        redef fun first do return _item

        redef fun is_empty do return false

        redef fun length do return 1

        redef fun has(an_item) do return _item == an_item

        redef fun has_only(an_item) do return _item == an_item

        redef fun count(an_item)
        do
                if _item == an_item then
                        return 1
                else
                        return 0
                end
        end

        redef fun iterator do return new ContainerIterator[E](self)

        # Create a new instance with a given initial value.
        init(e: E) do _item = e

        # The stored item
        readable writable var _item: E
end

# This iterator is quite stupid since it is used for only one item.
class ContainerIterator[E]
special Iterator[E]
        redef fun item do return _container.item

        redef fun next do _is_ok = false

        init(c: Container[E]) do _container = c

        redef readable var _is_ok: Bool = true

        var _container: Container[E]
end

# Items can be removed from this collection
interface RemovableCollection[E]
special Collection[E]
        # Remove all items
        fun clear is abstract

        # Remove an occucence of `item'
        fun remove(item: E) is abstract

        # Remove all occurences of `item'
        fun remove_all(item: E) do while has(item) do remove(item)
end

# Items can be added to these collections.
interface SimpleCollection[E]
special RemovableCollection[E]
        # Add an item in a collection.
        # Ensure col.has(item)
        fun add(item: E) is abstract

        # Add each item of `coll`.
        fun add_all(coll: Collection[E]) do for i in coll do add(i)
end

# Abstract sets.
#
# Set contains contains only one element with the same value (according to =).
#    var s : Set[E]
#    var a = "Hello"
#    var b = "Hello"
#    ...
#    s.add(a)
#    s.has(b) # --> true
interface Set[E]
special SimpleCollection[E]

        redef fun has_only(item)
        do
                var l = length
                if l == 1 then
                        return has(item)
                else if l == 0 then
                        return true
                else
                        return false
                end
        end

        # Only 0 or 1
        redef fun count(item)
        do
                if has(item) then
                        return 1
                else
                        return 0
                end
        end

        # Synonym of remove since there is only one item
        redef fun remove_all(item) do remove(item)
end

interface MapRead[K, E]
special Collection[E]
        # Get the item at `key'.
        fun [](key: K): E is abstract

        # Is there an item at `key'.
        fun has_key(key: K): Bool is abstract

        redef fun iterator: MapIterator[K, E] is abstract
end

# Maps are associative collections: `key' -> `item'.
#
# The main operator over maps is [].
#
#     var map: Map[U, V]
#     ...
#     map[u1] = v1      # Associate 'v1' to 'u1'
#     map[u2] = v2      # Associate 'v2' to 'u2'
#     map[u1]            # -> v1
#     map[u2]            # -> v2
#     map.has_key(u1)    # -> true
#     map.has_key(u3)    # -> false
interface Map[K, E]
special RemovableCollection[E]
special MapRead[K, E]
        # Set the`item' at `key'.
        fun []=(key: K, item: E) is abstract

        # Remove the item at `key'
        fun remove_at(key: K) is abstract

        # Add each (key,value) of `map' into `self'.
        # If a same key exists in `map' and `self', then the value in self is discarded.
        fun recover_with(map: Map[K, E])
        do
                var i = map.iterator
                while i.is_ok do
                        self[i.key] = i.item
                        i.next
                end
        end
end

# Iterators for Map.
interface MapIterator[K, E]
special Iterator[E]
        # The key of the current item.
        fun key: K is abstract

        # Set a new `item' at `key'.
        #fun item=(item: E) is abstract
end

# Indexed collection are ordoned collections.
# The first item is 0. The last is `length'-1.
interface IndexedCollectionRead[E]
special MapRead[Int, E]
        # Get the first item.
        # Is equivalent with `self'[0].
        redef fun first
        do
                assert not_empty: not is_empty
                return self[0]
        end
        
        # Get the last item.
        # Is equivalent with `self'[`length'-1].
        fun last: E
        do
                assert not_empty: not is_empty
                return self[length-1]
        end

        # Return the index of the first occurence of `item'.
        # Return -1 if `item' is not found
        fun index_of(item: E): Int
        do
                var i = iterator
                while i.is_ok do
                        if i.item == item then return i.index
                        i.next
                end
                return -1
        end

        redef fun iterator: IndexedIterator[E] is abstract
end

# Indexed collection are ordoned collections.
# The first item is 0. The last is `length'-1.
interface IndexedCollection[E]
special IndexedCollectionRead[E]
special Map[Int, E]
special SimpleCollection[E]
        # Set the first item.
        # Is equivalent with `self'[0] = `item'.
        fun first=(item: E)
        do self[0] = item end

        # Set the last item.
        # Is equivalent with `self'[length-1] = `item'.
        fun last=(item: E) 
        do 
                var l = length
                if l > 0 then
                        self[l-1] = item
                else
                        self[0] = item
                end
        end

        # A synonym of `push'
        redef fun add(e) do push(e)

        # Add an item after the last.
        fun push(e: E) is abstract

        # Add each item of `coll` after the last.
        fun append(coll: Collection[E]) do for i in coll do push(i)

        # Remove the last item.
        fun pop: E is abstract

        # Add an item before the last.
        fun unshift(e: E) is abstract

        # Remove the first item.
        # The second item become the first.
        fun shift: E is abstract

end

# Iterators on indexed collections.
interface IndexedIterator[E]
special MapIterator[Int, E]
        # The index of the current item.
        fun index: Int is abstract

        # A synonym of index.
        redef fun key do return index
end

# Associatives arrays that internally uses couples to represent each (key, value) pairs.
interface CoupleMap[K, E]
special Map[K, E]
        # Return the couple of the corresponding key
        # Return null if the key is no associated element
        protected fun couple_at(key: K): nullable Couple[K, E] is abstract

        redef fun [](key)
        do
                var c = couple_at(key)
                if c == null then
                        abort
                else
                        return c.second
                end
        end

        redef fun has_key(key) do return couple_at(key) != null
end

# Iterator on CoupleMap
#
# Actually is is a wrapper around an iterator of the internal array of the map.
class CoupleMapIterator[K, E]
special MapIterator[K, E]
        redef fun item do return _iter.item.second
        
        #redef fun item=(e) do _iter.item.second = e

        redef fun key do return _iter.item.first

        redef fun is_ok do return _iter.is_ok

        redef fun next
        do 
                _iter.next
        end

        var _iter: Iterator[Couple[K,E]]

        init(i: Iterator[Couple[K,E]]) do _iter = i
end

# Some tools ###################################################################

# Two objects in a simple structure.
class Couple[F, S]

        # The first element of the couple.
        readable writable var _first: F

        # The second element of the couple.
        readable writable var _second: S

        # Create a new instance with a first and a second object.
        init(f: F, s: S)
        do
                _first = f
                _second = s
        end
end