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option.n
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option.n
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/*
* Copyright (c) 2003-2008 The University of Wroclaw.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the University may not be used to endorse or promote
* products derived from this software without specific prior
* written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN
* NO EVENT SHALL THE UNIVERSITY BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
* TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
using Nemerle.Utility;
using System.Diagnostics;
namespace Nemerle.Core
{
/**
* The optional value variant.
*/
[DebuggerNonUserCode]
[System.Serializable]
[Nemerle.MarkOptions (System.Serializable)]
[Nemerle.MarkOptions (DebuggerNonUserCode)]
public variant option[T] : System.IEquatable[option[T]]
{
| None
| Some { val : T; }
/**
* Pretty prints the optional value.
*/
public override ToString () : string
{
match (this){
| Some (x) when x : object == null => "Some()"
| Some (x) => "Some (" + x.ToString () + ")"
| None => "None"
}
}
/**
* Typesafe equality checks.
*/
[Nemerle.OverrideObjectEquals]
public Equals (o : option [T]) : bool
implements System.IEquatable[option[T]].Equals
{
Nemerle.Core.Option.Equals (this, o)
}
/**
* Structural HashCode provider
*/
public override GetHashCode () : int
{
match (this) {
| None => 0
| Some (x) => x.GetHashCode ()
}
}
public IsSome : bool
{
get { this is Some (_) }
}
public IsNone : bool
{
get { this is None () }
}
public WithDefault (val : T) : T
{
match (this) {
| Some (v) => v
| None => val
}
}
public HasValue : bool
{
get { this is Some (_) }
}
public Value : T
{
get {
match (this) {
| Some (x) => x
| None =>
throw System.ArgumentException ("option.Value")
}
}
}
public static @:[TFrom](value : System.Nullable[TFrom]) : option[TFrom]
where TFrom: struct
{
if (value.HasValue) Some(value.Value) else None()
}
}
/**
* Operations on optional values
*/
public module Option
{
/**
* Safe equality check
*/
public Equals [T] (x : option [T], y : option [T]) : bool
{
| (Some (a), Some (b)) => a.Equals (b)
| (None, None) => true
| (null, null) => throw System.ArgumentException ("option can't be null")
| _ => false
}
/**
* Safe optional value mapping.
*/
public Map [T, TTo] (this x : option [T], f : T -> TTo) : option [TTo]
{
match (x) {
| Some (x) => Some (f (x))
| null => throw System.ArgumentException ("option can't be null")
| None => None ()
}
}
/**
* Same as ignore (Map (x, f)).
*/
public Iter [T] (this x : option [T], f : T -> void) : void
{
match (x) {
| Some (x) => f (x)
| null | None => ()
}
}
/**
* Checks if the optional value is present.
*/
public IsSome [T] (x : option [T]) : bool
{
match (x) {
| Some => true
| _ => false
}
}
/**
* Returns `true' if the optional value is not present.
*/
public IsNone[T] (x : option [T]) : bool
{
match (x) {
| None => true
| null => throw System.ArgumentException ("option can't be null")
| _ => false
}
}
/**
* Unwraps an optional value; throws an argument exception
* if the value is not present.
*/
public UnSome [T] (this x : option [T]) : T
{
match (x) {
| Some (x) => x
| _ => throw System.ArgumentException ("Option.UnSome")
}
}
/**
* Converts nullable value to optional value.
*/
public ToOption[T](this x : System.Nullable[T]) : option[T]
where T: struct
{
x
}
}
public module ValueOptionStatic
{
public VSome[T](value : T) : ValueOption[T] { ValueOption(value) }
public VNone[T]() : ValueOption[T] { default(ValueOption[T]) }
}
[ExtensionPattern(VSome(value) = ValueOption where(HasValue=true, Value=value))]
[ExtensionPattern(VNone() = ValueOption where(HasValue=false))]
public struct ValueOption[T]
{
_value : T;
public Value : T
{
get
{
if (HasValue) _value
else assert(false, "try use Value when it not set");
}
}
public GetValueOrDefault() : T { _value }
public HasValue : bool;
public IsSome : bool
{
get { HasValue }
}
public IsNone : bool
{
get { !HasValue }
}
public this(value : T)
{
_value = value;
HasValue = true;
}
public static None() : ValueOption[T] { default(ValueOption[T]) }
public static Some(value : T) : ValueOption[T] { ValueOption(value) }
}
}