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Loyc.Collections.EmptyList< T > Class Template Reference

Helper class: EmptyList{T}.Value is a read-only empty list. More...


Source file:
Inheritance diagram for Loyc.Collections.EmptyList< T >:
Loyc.Collections.IRange< out T > Loyc.Collections.IIsEmpty Loyc.Collections.IBRange< out T > Loyc.Collections.IListSource< out T > Loyc.ICloneable< out T > Loyc.Collections.IFRange< out T > Loyc.ICloneable< out T > Loyc.ICloneable< out T > Loyc.Collections.IIsEmpty

Remarks

Helper class: EmptyList{T}.Value is a read-only empty list.

Public static fields

static readonly EmptyList< T > Value = new EmptyList<T>()
 

Properties

this[int index] [get, set]
 
int Count [get]
 
bool IsReadOnly [get]
 
bool IsEmpty [get]
 
Front [get]
 
Back [get]
 
- Properties inherited from Loyc.Collections.IBRange< out T >
Back [get]
 Returns the value of the last item in the range. More...
 
- Properties inherited from Loyc.Collections.IFRange< out T >
Front [get]
 Returns the first value in the range, without popping it. More...
 
- Properties inherited from Loyc.Collections.IIsEmpty
bool IsEmpty [get]
 

Public Member Functions

int IndexOf (T item)
 
void Insert (int index, T item)
 
void RemoveAt (int index)
 
TryGet (int index, out bool fail)
 Gets the item at the specified index, and does not throw an exception on failure. More...
 
void Add (T item)
 
void Clear ()
 
bool Contains (T item)
 
void CopyTo (T[] array, int arrayIndex)
 
bool Remove (T item)
 
IEnumerator< T > GetEnumerator ()
 
IRange< T > Slice (int start, int count)
 Returns a sub-range of this list. More...
 
PopBack (out bool fail)
 Removes the last item from the range and returns it. More...
 
PopFront (out bool fail)
 Removes the first item from the range and returns it. More...
 

Member Function Documentation

T Loyc.Collections.EmptyList< T >.PopBack ( out bool  fail)
inline

Removes the last item from the range and returns it.

Parameters
failReceives the current value of IsEmpty.
Returns
The first item of the range, or default(T) if IsEmpty.

The remarks of IFRange{T}.PopFront apply to this method.

Implements Loyc.Collections.IBRange< out T >.

T Loyc.Collections.EmptyList< T >.PopFront ( out bool  fail)
inline

Removes the first item from the range and returns it.

Parameters
failReceives the current value of IIsEmpty.IsEmpty.
Returns
The first item of the range, or default(T) if IsEmpty.

This method is a little unweildy in plain C#, but in EC# it will be a bit more convenient to use via extension methods like PopFirst(ref this Range range, T defaultValue) and PopFirst(ref this Range range), which are illegal in plain C#.

I wanted to give this method the signature "bool PopFirst(out T first)" but the generic parameter "T" is covariant, i.e. it is marked "out T" which, ironically, is not compatible with "out T" parameters, only with return values.

Implements Loyc.Collections.IFRange< out T >.

IRange<T> Loyc.Collections.EmptyList< T >.Slice ( int  start,
int  count 
)
inline

Returns a sub-range of this list.

Parameters
startThe new range will start at this index in the current list (this location will be index [0] in the new range).
countThe desired number of elements in the new range, or int.MaxValue to get all elements until the end of the list.
Returns
Returns a sub-range of this range.
Exceptions
ArgumentExceptionThe start index was below zero.

The (start, count) range is allowed to be invalid, as long as start is zero or above.

  • If count is below zero, or if start is above the original Count, the Count of the new slice is set to zero.
  • if (start + count) is above the original Count, the Count of the new slice is reduced to this.Count - start. Implementation note: do not compute (start + count) because it may overflow. Instead, test whether (count > this.Count - start).

Most collections should use the following implementation:

IRange<T> IListSource<T>.Slice(int start, int count) { return Slice(start, count); }
public Slice_<T> Slice(int start, int count) { return new Slice_<T>(this, start, count); }

Implements Loyc.Collections.IListSource< out T >.

T Loyc.Collections.EmptyList< T >.TryGet ( int  index,
out bool  fail 
)
inline

Gets the item at the specified index, and does not throw an exception on failure.

Parameters
indexAn index in the range 0 to Count-1.
failA flag that is set on failure.
Returns
The element at the specified index, or default(T) if the index is not valid.

In my original design, the caller could provide a value to return on failure, but this would not allow T to be marked as "out" in C# 4. For the same reason, we cannot have a ref/out T parameter. Instead, the following extension methods are provided:

bool TryGet(int index, ref T value);
T TryGet(int, T defaultValue);

Implements Loyc.Collections.IListSource< out T >.