idioms

Is there anything more idiomatic than the following? foo.class == String I think you are looking for instance_of? . is_a? and kind_of? will return true for instances from derived classes. class X < String end foo = X.new foo.is_a? String # true foo.kind_of? String # true foo.instance_of? String # false foo.instance_of? X # true A more duck-typing approach would be to say foo.respond_to?(:to_str) to_str indicates that an object's class may not be an actual descendant of the String, but the object itself is very much string-like (stringy?). Federico Builes You can do: foo.instance_of?(String)

What are some C++ related idioms, misconceptions, and gotchas that you've learnt from experience? An example: class A { public: char s[1024]; char *p; A::A() { p = s; } void changeS() const { p[0] = 'a'; } }; Even know changeS is a const member function, it is changing the value of the object. So a const member function only means that it will treat all variables as const, and it does not mean that it will actually keep all members const. (why? the const keyword on the member function treats char *p; as char * const p; And not as const char *p; Which therefore means that p can't point to

I found the type alias below in an Scheme interpreter I'm studying. While evaluating the AST, it recognizes a function either as a natively supported function, or as a user defined function. I understand the second part of the Enum definition, but the first part eludes me. pub enum Function { Native(ValueOperation), Scheme(Vec<String>, Vec<Value>, Rc<RefCell<Environment>>), } type ValueOperation = fn(&[Value], Rc<RefCell<Environment>>) -> Result<Value, RuntimeError>; How does this type alias work? Does this definition say that a ValueOperation is just a shorthand for a function signature? I

I was reading through Go's compress/flate package, and I found this odd piece of code [1]: n := int32(len(list)) list = list[0 : n+1] list[n] = maxNode() In context, list is guaranteed to be pointing to an array with more data after. This is a private function, so it can't be misused outside the library. To me, this seems like a scary hack that should be a runtime exception. For example, the following D code generates a RangeError: auto x = [1, 2, 3]; auto y = x[0 .. 2]; y = y[0 .. 3]; Abusing slices could be done more simply (and also look more safe) with the following: x := []int{1, 2, 3} y

Possible Duplicate: Python try-else I'm not seeing the benefit of it, at least based on the example I just read in Dive Into Python: try: from EasyDialogs import AskPassword except ImportError: getpass = default_getpass else: getpass = AskPassword ( http://www.diveintopython.net/file_handling/index.html ) Why couldn't you achieve the same effect with the shorter/simpler: try: from EasyDialogs import AskPassword getpass = AskPassword except ImportError: getpass = default_getpass What am I missing? Izkata There isn't an advantage in the example, except possibly for style. It's generally a good

PHPeoples, I'm so tired of doing this $value = isset($arr[$key]) ? $arr[$key] : null; Or this $value = array_key_exists($key, $arr) ? $arr[$key] : null; Don't nobody tell me to do $arr = array(1); $key = 5; $value = $arr[$key]; // Notice: Undefined offset: 5 I got bronchitis. Ain't nobody got time f'dat. I could make a function, I guess... function array_get(Array $arr, $key, $default=null) { return array_key_exists($key, $arr) ? $arr[$key] : $default ; } But is this the best (most idiomatic) way? More elegant way of doing it: function ifsetor(&$value, $default = null) { return isset($value) ?