I think a better approach is to encapsulate the many fields of your multi-dimensional key into a class / struct. For example struct Key { public readonly int Dimension1; public readonly bool Dimension2; public Key(int p1, bool p2) { Dimension1 = p1; Dimension2 = p2; } // Equals and GetHashCode ommitted } Now you can … Read more
Consider using MATLAB’s map class: containers.Map. Here is a brief overview: Creation: >> keys = {‘Jan’, ‘Feb’, ‘Mar’, ‘Apr’, ‘May’, ‘Jun’, … ‘Jul’, ‘Aug’, ‘Sep’, ‘Oct’, ‘Nov’, ‘Dec’, ‘Annual’}; >> values = {327.2, 368.2, 197.6, 178.4, 100.0, 69.9, … 32.3, 37.3, 19.0, 37.0, 73.2, 110.9, 1551.0}; >> rainfallMap = containers.Map(keys, values) rainfallMap = containers.Map handle … Read more
I had the same need and did some research and ended up using libcfu It’s simple and readable so if I have a need to modify, I can do it without spending too much time to understand. It’s also of BSD license. No need to change my structs (to embed say a next pointer) I … Read more
Yes, it is a hash mapping or hash table. You can read a description of python’s dict implementation, as written by Tim Peters, here. That’s why you can’t use something ‘not hashable’ as a dict key, like a list: >>> a = {} >>> b = [‘some’, ‘list’] >>> hash(b) Traceback (most recent call last): … Read more
Shouldn’t be too hard. Something like this should do the trick: # Create a PSCustomObject (ironically using a hashtable) $ht1 = @{ A = ‘a’; B = ‘b’; DateTime = Get-Date } $theObject = new-object psobject -Property $ht1 # Convert the PSCustomObject back to a hashtable $ht2 = @{} $theObject.psobject.properties | Foreach { $ht2[$_.Name] = … Read more
Another option, if portability is not your main concern, is to use associative arrays that are built in to the shell. This should work in bash 4.0 (available now on most major distros, though not on OS X unless you install it yourself), ksh, and zsh: declare -A newmap newmap[name]=”Irfan Zulfiqar” newmap[designation]=SSE newmap[company]=”My Own Company” … Read more
System.Collections.Generic.Dictionary<TKey, TValue> and System.Collections.Hashtable classes both maintain a hash table data structure internally. None of them guarantee preserving the order of items. Leaving boxing/unboxing issues aside, most of the time, they should have very similar performance. The primary structural difference between them is that Dictionary relies on chaining (maintaining a list of items for each … Read more
If you are on .NET 4.0 use a Tuple: lookup = new Dictionary<Tuple<TypeA, TypeB, TypeC>, string>(); If not you can define a Tuple and use that as the key. The Tuple needs to override GetHashCode, Equals and IEquatable: struct Tuple<T, U, W> : IEquatable<Tuple<T,U,W>> { readonly T first; readonly U second; readonly W third; public … Read more
Hash tables deal with collisions in one of two ways. Option 1: By having each bucket contain a linked list of elements that are hashed to that bucket. This is why a bad hash function can make lookups in hash tables very slow. Option 2: If the hash table entries are all full then the … Read more
By definition, the put command replaces the previous value associated with the given key in the map (conceptually like an array indexing operation for primitive types). The map simply drops its reference to the value. If nothing else holds a reference to the object, that object becomes eligible for garbage collection. Additionally, Java returns any … Read more