-1 is a reserved value at the C level of CPython which prevents hash functions from being able to produce a hash value of -1. As noted by DSM, the same is not true in IronPython and PyPy where hash(-1) != hash(-2). See this Quora answer: If you write a type in a C extension … Read more
You can find a good (and fast) hash function, and an interesting read, at http://www.azillionmonkeys.com/qed/hash.html The only time you should not check for collisions, is if you use a perfect hash — a good old fashioned lookup table, like gperf.
std::hash is a class type. What you are doing here is constructing a temporary std::hash with hash<string>() and then (sd.isbn()) calls the operator() of that temporary passing it sd.isbn(). It would be the same as std::hash<std::string> temp; return temp(sd.isbn()); For more reading on using objects that have a operator() see: C++ Functors – and their … Read more
Java’s Set and Map interfaces specify two very different collection types. A Set is just what it sounds like: a collection of distinct (non-equal) objects, with no other structure. A Map is, conceptually, also just what it sounds like: a mapping from a set of objects (the distinct keys) to a collection of objects (the … Read more
You can create the following pre-request script provided your parameters are defined environment variables. You would need to tweak this example if they are defined in some other fashion. // Access your env variables like this var str_1 = environment.variable_1 + environment.variable_2; // Or get your request parameters var str_2 = request.data[“foo”] + request.data[“bar”]; // … Read more
What you need is Pretty Print pprint module: from pprint import pprint # Build the tree somehow with open(‘output.txt’, ‘wt’) as out: pprint(myTree, stream=out)
It is a lot more complicated than meets the eye. For starters, give the key2 value a completely different string. Notice how the hash code is still the same: var k1 = new TheKey(17, “abc”); var k2 = new TheKey(17, “def”); System.Diagnostics.Debug.Assert(k1.GetHashCode() == k2.GetHashCode()); Which is quite valid, the only requirement for a hash code … Read more
If all you need the hash for is membership, consider using a Set: Set Set implements a collection of unordered values with no duplicates. This is a hybrid of Array’s intuitive inter-operation facilities and Hash’s fast lookup. Set is easy to use with Enumerable objects (implementing each). Most of the initializer methods and binary operators … Read more
Hashes are much faster for lookups: require ‘benchmark’ Document = Struct.new(:id,:a,:b,:c) documents_a = [] documents_h = {} 1.upto(10_000) do |n| d = Document.new(n) documents_a << d documents_h[d.id] = d end searchlist = Array.new(1000){ rand(10_000)+1 } Benchmark.bm(10) do |x| x.report(‘array’){searchlist.each{|el| documents_a.any?{|d| d.id == el}} } x.report(‘hash’){searchlist.each{|el| documents_h.has_key?(el)} } end # user system total real #array 2.240000 … Read more
If you want column headers and you have multiple hashes: require ‘csv’ hashes = [{‘a’ => ‘aaaa’, ‘b’ => ‘bbbb’}] column_names = hashes.first.keys s=CSV.generate do |csv| csv << column_names hashes.each do |x| csv << x.values end end File.write(‘the_file.csv’, s) (tested on Ruby 1.9.3-p429)