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Comment by lukev | Hacker News Reader

I'd got a step further and say that in business software, named parameters are preferable for all but the smallest functions.

Using curried OR tuple arg lists requires remembering the name of an argument by its position. This saves room on the screen but is mental overhead.

The fact is that arguments do always have names anyway and you always have to know what they are.

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I want to agree, but there is the tension that in business code, what you pass as arguments is very often already named like the parameter, so having to indicate the parameter name in the call leads to a lot of redundancy. And if you’re using domain types judiciously, the types are typically also different, hence (in a statically-typed language) there is already a reduced risk of passing the wrong parameter.

Maybe there could be a rule that parameters have to be named only if their type doesn’t already disambiguate them and if there isn’t some concordance between the naming in the argument expression and the parameter, or something along those lines. But the ergonomics of that might be annoying as well.

This is an issue in Python but less so in languages like JavaScript that support "field name punning", where you pass named arguments via lightweight record construction syntax, and you don't need to duplicate a field name if it's the same as the local variable name you're using for that field's value.

That forces you to name the variable identically to the parameter. For example, you may want to call your variable `loggedInUser` when the fact that the user is logged in is important for the code’s logic, but then you can’t pass it as-is for a field that is only called `user`. Having to name the parameter leads to routinely having to write `foo: blaFoo` because just `blaFoo` wouldn’t match, or else to drop the informative `bla`. That’s part of the tension I was referring to.

OCaml has a neat little feature where it elides the parameter and variable name if they're the same:

  let warn_user ~message = ... (* the ~ makes this a named parameter *)

  let error = "fatal error!!" in
  warn_user ~message:error; (* different names, have to specify both *)

  let message = "fatal error!!" in
  warn_user ~message; (* same names, elided *)

The elision doesn't always kick in, because sometimes you want the variable to have a different name, but in practice it kicks in a lot, and makes a real difference. In a way, cases when it doesn't kick in are also telling you something, because you're crossing some sort of context boundary where some value is called different things on either side.

I write plenty of business code, and I do not like even the possibility of a mistake like:

    fn compute_thing(cost: whatever, num_widgets: whatever) -> Whatever;

    let cost = …;
    let num_widgets = …;
    let result = compute_thing(num_widgets, cost);

(This can by most any language including Haskell or Lean, with slightly different syntax.)

One can prevent this very verbosely with the Builder pattern. Or one can use named parameters in languages that support them.

An interesting analogue is tensor math. In Einstein’s work, there were generally four dimensions and you probably wouldn’t lose track of which letter was which. In linear algebra, at least at the high school or early undergrad level, there are usually vectors and tensors and, well, that’s it. But in data crunching or modern ML, tensors have all kinds of cool axes, and for some reason we usually just identify them by which slot they are in the order that they happen to be in in the input tensor. Some people try to creatively make this “type safe” by specializing on the length of the dimension, which is an incomplete solution at best. I would love to see adoption of some solution that gives these things explicit names and does not ever guess which axis is being referenced.

(I find 95% of ML code and a respectable fraction of papers and descriptions to be locally incomprehensible because you need to look somewhere else to figure out what on Earth A • B' actually means.

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