/// <summary>
/// Solves the backpacking problem, and prints out information
/// about the solution.
/// </summary>
public void Run()
{
Solve(TheBackPack.WeightCapacityLeft);
TheBackPack.PrintContent();
System.Console.WriteLine();
TheVault.PrintContent();
}
public static void AlsoNeedHelp()
{
using (RwLck lck = TheVault.Lock())
{
IllegalWrapper wrapper = default;
wrapper.SetLockedResource(in lck);
lck.AppendLine("Goodbye cruel world!");
Console.WriteLine(wrapper.WrappedLockedResource.ToString());
}
}
public override void Solve(double capacityLeft)
{
string description = PickNextItemFromVault(capacityLeft);
if (description != string.Empty)
{
BackPackItem item = TheVault.RemoveItem(description);
TheBackPack.AddItem(item);
Solve(TheBackPack.WeightCapacityLeft);
}
}
/// <summary>
/// Naive solver implementation (but it's recursive!)
/// </summary>
public override void Solve(double capacityLeft)
{
// Keep adding the first element from the vault, until
// the first element cannot fit into the backpack...
if (TheVault.Items[0].Weight <= capacityLeft)
{
BackPackItem item = TheVault.RemoveItem(TheVault.Items[0].Description);
TheBackPack.AddItem(item);
Solve(TheBackPack.WeightCapacityLeft);
}
}
//internal static void ShowMoreDetailedBug92Fix()
//{
// //protected resources are now decorated with the NoCopy attribute.
// //If a ref struct contains a field of the same type as the protected resource,
// //it is now prohibited to allow these two to overlap in scope.
// //ref struct wrapper with containing non-static field of type StringBuilderRwLockedResource
// RwLockWrapper wrapperCopy=default;
// {
// using (var lck = TheVault.Lock())
// {
// lck.AppendLine("We don't need no education ... ");
// //Bug 92 fix -- uncommenting the following line triggers compilation error
// //bug 92 fix -- a ref struct that has a non-static field of the same type as a locked
// //bug 92 fix -- resource object, may not appear in the same scope as the locked
// //bug 92 fix -- resource object, hence, following line will cause compilation error.
// using (wrapperCopy = new RwLockWrapper(in lck, "Foobar"))
// {
// Console.WriteLine(wrapperCopy.ToString());
// }
// }
// }
// //the locked resource has been returned to vault and this line causes unsynchronized access
// Console.WriteLine(wrapperCopy.ToString());
//}
//internal static void ShowMoreDetailedBug92AnotherVariation()
//{
// //protected resources are now decorated with the NoCopy attribute.
// //If a ref struct contains a field of the same type as the protected resource,
// //it is now prohibited to allow these two to overlap in scope.
// //ref struct wrapper with containing non-static field of type StringBuilderRwLockedResource
// string fizz;
// {
// using (var lck = TheVault.Lock())
// {
// lck.AppendLine("We don't need no education ... ");
// //Bug 92 fix -- uncommenting the following line triggers compilation error
// //bug 92 fix -- a ref struct that has a non-static field of the same type as a locked
// //bug 92 fix -- resource object, may not appear in the same scope as the locked
// //bug 92 fix -- resource object, hence, following line will cause compilation error.
// var wrapperCopy = new RwLockWrapper(in lck, "Foobar");
// fizz = wrapperCopy.ToString();
// }
// }
// //the locked resource has been returned to vault and this line causes unsynchronized access
// Console.WriteLine(fizz);
//}
internal static void Bug92StillAProblem()
{
using var lck = TheVault.Lock();
lck.AppendLine("We don't need no education ... ");
//Bug 92 fix -- uncommenting the following line triggers compilation error
//bug 92 fix -- a ref struct that has a non-static field of the same type as a locked
//bug 92 fix -- resource object, may not appear in the same scope as the locked
//bug 92 fix -- resource object, hence, following line will cause compilation error.
//using RwLockWrapper wrapperCopy = new RwLockWrapper(in lck, "Foobar");
//Console.WriteLine(wrapperCopy.ToString());
}
public static void HelpMe()
{
using RwLck lck = TheVault.Lock();
//bad
IllegalWrapper wrapper = IllegalWrapper.CreateCopyInSneakyWay(in lck, DateTime.Now);
//also bad
wrapper.SetLockedResource(in lck);
lck.AppendLine("Hi mom!");
Console.WriteLine(wrapper.WrappedLockedResource.ToString());
}
public override void Solve(double capacityLeft)
{
//sort by weight
List <BackPackItem> items = new List <BackPackItem>();
foreach (BackPackItem item in TheVault.Items)
{
items.Add(item);
}
items = items.OrderBy(o => o.Weight).ToList();
items.Reverse();
if (items[0].Weight <= capacityLeft)
{
BackPackItem item = TheVault.RemoveItem(items[0].Description); //vault remove item
TheBackPack.AddItem(items[0]); //backpack add item
Solve(TheBackPack.WeightCapacityLeft); //recursive
}
}
public override void Solve(double capacityLeft)
{
BackPackItem currentItem = TheVault.Items[0];
foreach (BackPackItem item in TheVault.Items)
{
if ((item.Value / item.Weight) > (currentItem.Value / currentItem.Weight))
{
currentItem = item;
}
}
if (currentItem.Weight <= capacityLeft)
{
TheVault.RemoveItem(currentItem.Description);
TheBackPack.AddItem(currentItem);
Solve(TheBackPack.WeightCapacityLeft);
}
else //most valuable item (by ratio) weighs more than we have room for
{
List <BackPackItem> lowWeightItems = new List <BackPackItem>();
foreach (BackPackItem item in TheVault.Items)
{
if (item.Weight < capacityLeft)
{
lowWeightItems.Add(item);
}
}
lowWeightItems = lowWeightItems.OrderBy(o => o.Value).ToList();
if (lowWeightItems.Count > 0)
{
if (lowWeightItems[0].Weight <= capacityLeft)
{
TheVault.RemoveItem(lowWeightItems[0].Description);
TheBackPack.AddItem(lowWeightItems[0]);
Solve(TheBackPack.WeightCapacityLeft);
}
}
}
}
/// <summary>
/// Locked resource objects should never be passed by value ... takes too long and
/// is dangerous
/// </summary>
internal static void ShowPassByValueNowForbidden()
{
using (RoLock lck = TheVault.RoLock())
{
//Pass by value... bad ... now will not compile
//Extensions.BadPrint3(lck);
//passed by mutable reference ... now will not compile
//Extensions.BadPrint4(ref lck);
//passed by write-mandatory mutable reference ... now will not compile
//Extensions.BadPrint5(out lck);
//this is ok -- passed with 'in'
Extensions.OkPrint(in lck);
//you will always have to use in parameter... this won't compile
//Extensions.OkPrint(lck);
//this is fine too ... passed by 'in'
//Extensions.OkPrint("Toodles", in lck);
//it still catches non-in passing if name-colon syntax used ... now will not compile
//Extensions.OkPrint(roLock: lck, text: "tiddly winks");
//of course if you use 'in' with the name colon it's ok
Extensions.OkPrint(roLock: in lck, text: "tiddly winks");
//Still works if extension method ...
//Can't pass by value to extension method ... will no longer compile
//lck.BadPrint();
//can't pass by mutable reference to extension method
//lck.BadPrint2(); //will no longer compile
//This is the correct way for extension method!
//extension method with signature:
//"void OkPrintToo(this in RoLock roLock);"
lck.OkPrintToo();
}
{
//all same problems detected if using declaration
using RoLock lck = TheVault.RoLock();
//Pass by value... bad ... now will not compile
//Extensions.BadPrint3(lck);
//passed by mutable reference ... now will not compile
//Extensions.BadPrint4(ref lck);
//passed by write-mandatory mutable reference ... now will not compile
//Extensions.BadPrint5(out lck);
//this is ok -- passed with 'in'
Extensions.OkPrint(in lck);
//you will always have to use in parameter... this won't compile
//Extensions.OkPrint(lck);
//this is fine too ... passed by 'in'
Extensions.OkPrint("Toodles", in lck);
//it still catches non-in passing if name-colon syntax used ... now will not compile
//Extensions.OkPrint(roLock: lck, text: "tiddly winks");
//of course if you use 'in' with the name colon it's ok
Extensions.OkPrint(roLock: in lck, text: "tiddly winks");
//Still works if extension method ...
//Can't pass by value to extension method ... will no longer compile
//lck.BadPrint();
//can't pass by mutable reference to extension method
//lck.BadPrint2(); //will no longer compile
//This is the correct way for extension method!
//extension method with signature:
//"void OkPrintToo(this in RoLock roLock);"
lck.OkPrintToo();
}
}
/// <summary>
/// Solves the backpacking problem, and prints out information
/// about the solution.
/// </summary>
public void Run()
{
Solve(TheBackPack.WeightCapacityLeft);
TheBackPack.PrintContent();
TheVault.PrintContent();
}
