Technically they’re copied, because when you use make, you are allocating something on the heap, so it’s technically a pointer behind the scenes. But the pointer type is not exposed, so they can be thought of as a reference type. EDIT: From the spec: The built-in function make takes a type T, which must be … Read more
When in doubt, pass by value. Now, you should only rarely be in doubt. Often values are expensive to pass and give little benefit. Sometimes you actually want a reference to a possibly mutating value stored elsewhere. Often, in generic code, you don’t know if copying is an expensive operation, so you err on the … Read more
Arguments are passed by value, unless the function signature specifies otherwise: in void foo(type arg), arg is passed by value regardless of whether type is a simple type, a pointer type or a class type, in void foo(type& arg), arg is passed by reference. In case of arrays, the value that is passed is a … Read more
Python passes references-to-objects by value. Python passes references-to-objects by value (like Java), and everything in Python is an object. This sounds simple, but then you will notice that some data types seem to exhibit pass-by-value characteristics, while others seem to act like pass-by-reference… what’s the deal? It is important to understand mutable and immutable objects. … Read more
There are two problems: Integer is pass by value, not by reference. Changing the reference inside a method won’t be reflected into the passed-in reference in the calling method. Integer is immutable. There’s no such method like Integer#set(i). You could otherwise just make use of it. To get it to work, you need to reassign … Read more
Call-by-value The R Language Definition says this (in section 4.3.3 Argument Evaluation) The semantics of invoking a function in R argument are call-by-value. In general, supplied arguments behave as if they are local variables initialized with the value supplied and the name of the corresponding formal argument. Changing the value of a supplied argument within … Read more
You can try using org.apache.commons.lang.mutable.MutableInt from Apache Commons library. There is no direct way of doing this in the language itself.
First of all, take in account that returning an object will always be more readable (and very similar in performance) than having it passed by reference, so could be more interesting for your project to return the object and increase readability without having important performance differences. If you want to know how to have the … Read more
What you are after is called partial function application. Don’t be fooled by those that don’t understand the subtle difference between that and currying, they are different. Partial function application can be used to implement, but is not currying. Here is a quote from a blog post on the difference: Where partial application takes a … Read more
Arrays can only be passed by reference, actually: void foo(double (&bar)[10]) { } This prevents you from doing things like: double arr[20]; foo(arr); // won’t compile To be able to pass an arbitrary size array to foo, make it a template and capture the size of the array at compile time: template<typename T, size_t N> … Read more