idioms

Presenting the Idiom I found an interesting but unexplained alternative to an accepted answer. The code clearly works in the REPL. For example: module Foo class Bar def baz end end end Foo.constants.map(&Foo.method(:const_get)).grep(Class) => [Foo::Bar] However, I don't fully understand the idiom in use here. In particular, I don't understand the use of &Foo , which seems to be some sort of closure, or how this specific invocation of #grep operates on the result. Parsing the Idiom So far, I've been able to parse bits and pieces of this, but I'm not really seeing how it all fits together. Here

Ok, consider this common idiom that most of us have used many times (I assume): class FooBarDictionary { private Dictionary<String, FooBar> fooBars; ... FooBar GetOrCreate(String key) { FooBar fooBar; if (!fooBars.TryGetValue(key, out fooBar)) { fooBar = new FooBar(); fooBars.Add(key, fooBar); } return fooBar; } } Does it have any kind of established name? (Yes, it's written in C#, but it can be "easily" transferred to C++. Hence that tag.) Lazy Loading http://en.wikipedia.org/wiki/Lazy_loading I always call such functions obtainSomething() . It sort of depends why you're doing it - the idiom

I'm looking into OCaml for the first time, having a bit of background with F# and Haskell. As such, a lot is familiar-looking, but one thing that isn't is the concept of "open" and "closed" unions (with the backtick and [< syntax). What are these useful for and how often are they used? Gilles 'SO- stop being evil' gasche's answer has good advice . I'm going to explain open and closed unions a bit more. First, you need to distinguish the two kinds of unions: basic variants (no backtick) and polymorphic variants (with backtick). Basic variants are generative: if you define two types with the

I'm trying to find a way to use a hash map in R, and after some searching I get the R-environment. But how can I iterate through all the items in an environment ? When I run the following code, I was expecting output like this : 1 2 But I get two lines of NULL instead, how can I get what I want ? map <- new.env(hash=T, parent=emptyenv()) assign('a', 1, map) assign('b', 2, map) for (v in ls(map)) { print(map$v) } The use of "$" inside a function where it is desired to interpret the input is a common source of programming error. Use instead the form object[[value]] (without the quotes.) for (v

I'm designing a class that defines a highly complex object with a ton (50+) of mostly optional parameters, many of which would have defaults (eg: $type = 'foo'; $width = '300'; $interactive = false; ). I'm trying to determine the best way to set up the constructor and instance/class variables in order to be able to: make it easy to use the class make it easy to auto-document the class (ie: using phpDocumentor) code this elegantly In light of the above, I don't want to be passing the constructor a ton of arguments. I will be passing it a single hash which contains the initialization values, eg:

This question already has an answer here: The Zen of Python [closed] 22 answers Python: Am I missing something? [closed] 16 answers I would be interested in knowing what the StackOverflow community thinks are the important language features (idioms) of Python. Features that would define a programmer as Pythonic. Python (pythonic) idiom - "code expression" that is natural or characteristic to the language Python. Plus, Which idioms should all Python programmers learn early on? Thanks in advance Related: Code Like a Pythonista: Idiomatic Python Python: Am I missing something? gahooa Python is a