I have a question regarding the usage of the Function.identity() method. Imagine the following code: Arrays.asList(“a”, “b”, “c”) .stream() .map(Function.identity()) // <- This, .map(str -> str) // <- is the same as this. .collect(Collectors.toMap( Function.identity(), // <– And this, str -> str)); // <– is the same as this. Is there any reason why you … Read more
Recently I started playing around with Python and I came around something peculiar in the way closures work. Consider the following code: adders=[None, None, None, None] for i in [0,1,2,3]: adders[i]=lambda a: i+a print adders[1](3) It builds a simple array of functions that take a single input and return that input added by a number. … Read more
In Ruby 1.8, there are subtle differences between proc/lambda on the one hand, and Proc.new on the other. What are those differences? Can you give guidelines on how to decide which one to choose? In Ruby 1.9, proc and lambda are different. What’s the deal? 14 Answers 14
How can I throw CHECKED exceptions from inside Java 8 streams/lambdas? In other words, I want to make code like this compile: public List<Class> getClasses() throws ClassNotFoundException { List<Class> classes = Stream.of(“java.lang.Object”, “java.lang.Integer”, “java.lang.String”) .map(className -> Class.forName(className)) .collect(Collectors.toList()); return classes; } This code does not compile, since the Class.forName() method above throws ClassNotFoundException, which is … Read more
I’m playing with lambdas in Java 8 and I came across warning local variables referenced from a lambda expression must be final or effectively final. I know that when I use variables inside anonymous class they must be final in outer class, but still – what is the difference between final and effectively final? 14 … Read more
When using external iteration over an Iterable we use break or return from enhanced for-each loop as: for (SomeObject obj : someObjects) { if (some_condition_met) { break; // or return obj } } How can we break or return using the internal iteration in a Java 8 lambda expression like: someObjects.forEach(obj -> { //what to … Read more
I’ve heard it said that multiline lambdas can’t be added in Python because they would clash syntactically with the other syntax constructs in Python. I was thinking about this on the bus today and realized I couldn’t think of a single Python construct that multiline lambdas clash with. Given that I know the language pretty … Read more
Closed. This question is opinion-based. It is not currently accepting answers. Want to improve this question? Update the question so it can be answered with facts and citations by editing this post. Closed 9 months ago. Improve this question I am looking at the MvcContrib Grid component and I’m fascinated, yet at the same time … Read more
In Java 8, methods can be created as Lambda expressions and can be passed by reference (with a little work under the hood). There are plenty of examples online with lambdas being created and used with methods, but no examples of how to make a method taking a lambda as a parameter. What is the … Read more
In Python 2.6, I want to do: f = lambda x: if x==2 print x else raise Exception() f(2) #should print “2” f(3) #should throw an exception This clearly isn’t the syntax. Is it possible to perform an if in lambda and if so how to do it? 15 Answers 15 The syntax you’re looking … Read more
