The difference between functions and methods

The difference between functions and methods
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Not in the world at large. There’s considerable variation in what different programming languages/paradigms call ‘code units’ with varying properties.

For example, pascal has functions that cannot change the values of their arguments, and procedures that cannot return values. Both would be called functions in C and JavaScript.

Common Lisp has defun to define functions because it is a lisp, but introduces defmethod to make something that’s highly similar, except [1] that it can be called when code calls a generic function defined by defgeneric (https://gigamonkeys.com/book/object-reorientation-generic-fu...; https://opendylan.org/intro-dylan/methods-generic-functions.... may be easier to understand because it, IMO, is better written and because, for many, Dylan’s pascal syntax is easier to understand)

Also, functional language purists will argue that functions must be pure (https://en.wikipedia.org/wiki/Pure_function), as they are in mathematics.

[1] I probably am ignoring/forgetting details, possibly even essential ones, here.

- Macros: arguments are interpreted as syntax, produces syntax, typically runs at compile-time. Their use case is anything functions can't do, e.g. define things or interpret syntax "abnormally" (different than parent language)

- Function: arguments are interpreted "normally" as values, outputs a value, usually runs at runtime.

- Method: function where one of the inputs is denoted as "self". Semantically there's no difference between `a.f(...)` and `f(a, ...)`, and some languages let you do both.

- Fexprs (https://en.wikipedia.org/wiki/Fexpr): weird macro/function hybrids, arguments are interpreted as syntax, but it produces a value and runs at runtime. I only know they exist in LISP and R, and only know how they work in R: certain operations (like assigning to a variable) evaluates the argument, the argument won't be evaluated if execution never reaches these operations (like if the assignment is in an `if` which doesn't get triggered; in other words, arguments are lazy), and special functions like `substitute` will extract the argument's syntax (e.g. if `⟦f⟧ = function(a) subsitute(a)`, `⟦f(foo(bar))⟧ = `; now if ⟦g⟧ = function(a) f(a)`, `⟦g(foo(bar))⟧ = `). Personally I don't like these, and prefer separate macros and functions, which I believe can accomplish anything fexprs can with less confusing semantics and accidental bugs. But they're an interesting concept I just listed here because they're like a function or macro, but neither.