/// <summary>
/// Determine a value by deriving it from a previously calculated value and then store the result
/// </summary>
/// <typeparam name="T">The type of the value</typeparam>
/// <param name="provider">Provider for previously defined value as well as the target to store the new value in</param>
/// <param name="name">The name of the value</param>
/// <param name="update">Function to derive a new value from an old one</param>
/// <param name="generate">Function to generate a new value if no old one existed</param>
/// <returns>The determined value</returns>
public static T DetermineHierarchicalValue <T>(this INamedDataCollection provider, TypedName <T> name, Func <T, T> update, Func <T> generate) where T : IEquatable <T>
{
Contract.Requires(provider != null);
Contract.Requires(update != null);
Contract.Requires(generate != null);
T value;
if (provider.TryGetValue <T>(name, out value))
{
var oldValue = value;
value = update(oldValue);
if (!EqualityComparer <T> .Default.Equals(oldValue, value))
{
provider.Set <T>(name, value);
}
}
else
{
value = generate();
provider.Set <T>(name, value);
}
return(value);
}
public override IReadOnlyList <Vector2> Apply(Func <double> random, INamedDataCollection metadata, IReadOnlyList <Vector2> footprint, IReadOnlyList <Vector2> basis, IReadOnlyList <Vector2> lot)
{
metadata.Set(new TypedName <T>(_key), _value);
return(footprint);
}
