However, in main, I pass the same variable, referenced both by a and by b. As f modifies b, it also modifies a, which it supposedly shouldn’t When f modifies what b refers to, it does not modify a. It modifies what a refers to, but that is okay since b is not const. It’s … Read more
Apologies for the short answer, but no, the C# language specification disallows it. See this answer to another question to see what happens when you try. It also says why you shouldn’t make the property just be a public field to get around the restriction. Hope this helps EDIT: You ask Why? You pass a … Read more
If you have reason to suspect there is a worthwhile performance gain to be had, cut it out with the rules of thumb and measure. The purpose of the advise you quote is that you don’t copy great amounts of data for no reason, but don’t jeopardize optimizations by making everything a reference either. If … Read more
Why can’t arrays be passed as function arguments? They can: void foo(const int (&myArray)[5]) { // `myArray` is the original array of five integers } In technical terms, the type of the argument to foo is “reference to array of 5 const ints”; with references, we can pass the actual object around (disclaimer: terminology varies … Read more
There are questions that already deal with the difference between passing by reference and passing by value. In essence, passing an argument by value to a function means that the function will have its own copy of the argument – its value is copied. Modifying that copy will not modify the original object. However, when … Read more
Effbot (aka Fredrik Lundh) has described Python’s variable passing style as call-by-object: http://effbot.org/zone/call-by-object.htm Objects are allocated on the heap and pointers to them can be passed around anywhere. When you make an assignment such as x = 1000, a dictionary entry is created that maps the string “x” in the current namespace to a pointer … Read more
What’s happening here is that you’re placing a pointer to a list in the hashmap, not the list itself. When you define List<SomeType> list; you’re defining a pointer to a list, not a list itself. When you do map.put(somekey, list); you’re just storing a copy of the pointer, not the list. If, somewhere else, you … Read more
This is a more general answer for future viewers. Callback types There are a few different types of predefined callbacks: final VoidCallback myVoidCallback = () {}; final ValueGetter<int> myValueGetter = () => 42; final ValueSetter<int> myValueSetter = (value) {}; final ValueChanged<int> myValueSetter = (value) {}; Notes: VoidCallback is an anonymous function that takes no arguments … Read more
Objects aren’t passed by reference. Objects aren’t passed at all. By default, the value of the argument is passed by value – whether that value is a value type value or a reference. If an object is modified via that reference, then that change will be visible to the calling code as well. In the … Read more