You can’t do what you’re trying to do: bash arrays are one-dimensional $ declare -A PERSONS $ declare -A PERSON $ PERSON[“FNAME”]=’John’ $ PERSON[“LNAME”]=’Andrew’ $ declare -p PERSON declare -A PERSON='([FNAME]=”John” [LNAME]=”Andrew” )’ $ PERSONS[1]=([FNAME]=”John” [LNAME]=”Andrew” ) bash: PERSONS[1]: cannot assign list to array member You can fake multidimensionality by composing a suitable array index … Read more
If you are going strictly for compatability then Bryan is correct. This is the best way to maintain your current semantics on top of a Dictionary. Expanding on it though. The reason the SyncRoot property was not directly added to the generic dictionary is that it’s a dangerous way to do synchronization. It’s only slighly … Read more
If you use .NET Reflector on the 3.5 class libraries you can see that the implementation of Dictionary actually stores the items in an array (which is resized as needed), and hashes indexes into that array. When getting the keys, it completely ignores the hashtable and iterates over the array of items. For this reason, … Read more
Use a LinkedHashMap. Hash table and linked list implementation of the Map interface, with predictable iteration order. This implementation differs from HashMap in that it maintains a doubly-linked list running through all of its entries. This linked list defines the iteration ordering, which is normally the order in which keys were inserted into the map … Read more
You need to use an explicit java.util.Iterator to iterate over the Map‘s entry set rather than being able to use the enhanced For-loop syntax available in Java 6. The following example iterates over a Map of Integer, String pairs, removing any entry whose Integer key is null or equals 0. Map<Integer, String> map = … … Read more
Hash-tables could not claim “amortized constant time insertion” if, for instance, the resizing was by a constant increment. In that case the cost of resizing (which grows with the size of the hash-table) would make the cost of one insertion linear in the total number of elements to insert. Because resizing becomes more and more … Read more
If you’re using C++11, you have access to the <unordered_map> and <unordered_set> headers. These provide classes std::unordered_map and std::unordered_set. If you’re using C++03 with TR1, you have access to the classes std::tr1::unordered_map and std::tr1::unordered_set, using the same headers (unless you’re using GCC, in which case the headers are <tr1/unordered_map> and <tr1/unordered_set> instead). In all cases, … Read more
If I know the number of keys and exactly what are those keys, is there any way in python to make a dict (or a hashtable) work more efficiently? I vaguely remember that if you know the keys, you can design the hash function smartly (perfect hash?) and allocate the space beforehand. Python doesn’t expose … Read more
Sure, you can use PowerShell’s native CliXml format: @{ a = 1 b = [pscustomobject]@{ prop = “value” } } | Export-Clixml -Path hashtable.ps1xml Deserialize with Import-CliXml: PS C:\> $ht = Import-CliXml hashtable.ps1xml PS C:\> $ht[‘b’].prop -eq ‘value’ True
First, it usually does not matter that much in practice. Most hash functions are “good enough”. But if you really care, you should know that it is a research subject by itself. There are thousand of papers about that. You can still get a PhD today by studying & designing hashing algorithms. Your second hash … Read more