Comment by amno | Hacker News Reader

Comment by amno | Hacker News Reader

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Hah! Why am I not surprised to see that nick on HN too :-)

I have no experience with LispWorks whatsoever, but I am curious, how did they implemented it if you know? I mean, how do they differ between calling first as a value or first as a function? In your example first could be a defvared to have some value, and then I might have called a function to produce some unrelated output. I mean it is a contrived example, and probably nobody types in a repl like that, but the language does not forbid it since white spaces are insignificant.

If they just treat the first token as operator always, than they could call any function with any arguments:

    CL-USER> op arg1 arg2 ... argN

but then they would have to eval all values at the start of repl by calling (symbol-function arg), instead of just type arg to examine a value. I don't think it would be a bad think in itself tbh; but I am not sure the win is big enough to introduce a new concept.

By the way, I think I have stumbled on some mailing list comment somewhere once, where they said, that Hemlock can use commands named more "english like", i.e. they can have names with spaces in it, not just the hyphenated function name as in Emacs. Do you know more about it, or how they have implemented it? I am just curious; seen your comments on Reddit, and if you are the same person, I understand you are well experienced and familiar with various Lisps and implementations; hope you don't mind asking. :)

> how did they implemented it if you know?

It's relatively easy:

a variable:

CL-USER> foo

an operator with no arguments:

CL-USER> (foo)

an operator with one or more arguments:

CL-USER> foo 1

CL-USER> foo 1 2

CL-USER> foo 1 (+ 1 2) (+ 3 4)

and so on.

> Hemlock can use commands named more "english like"

That's like Emacs (called Zmacs) on the Lisp Machine does it. It does not use hyphens at all. I can't remember how the first Emacs, the TECO Emacs, did it.

M-x compile-changed-definitions-of-buffer

is then

M-x Compile Changed Definition Of Buffer

Basically instead of hyphens it uses spaces.

In LispWorks & Zmacs one enters the command M-x Replace String <return> and then the editor prompts for the arguments.

> CL-USER> foo 1 > > CL-USER> foo 1 2 > > CL-USER> foo 1 (+ 1 2) (+ 3 4)

But then they do have the problem I mentions: they can't distinguish between calling (foo 1 (+ 1 2) (+ 3 4)) and calling (foo 1) (+ 1 2) (+ 3 4).

I don't think it is important ether, I certainly wouldn't type code like that in a repl either. I don't even know if sly/slime repl even support typing several expressions on the same line in repl. I am not at home to test it.

> Basically instead of hyphens it uses spaces. > > In LispWorks & Zmacs one enters the command M-x Replace String <return> and then the editor prompts for the arguments.

I understand, thanks.

I thought they were a bit more finicky about it. I think that could be relatively easily done in Emacs as well, but I don't see much gain to implement a M-x replacement like that. Especially with modern completion systems like Helm and fuzzy completing which basically don't care how we type.

Thank you for your time and answers.

> they can't distinguish between calling (foo 1 (+ 1 2) (+ 3 4)) and calling (foo 1) (+ 1 2) (+ 3 4).

It uses always (foo 1 (+ 1 2) (+ 3 4)). It uses the complete input.

> I don't even know if sly/slime repl even support typing several expressions on the same line in repl.

Most Lisp REPLs use multiline input. Here LispWorks requires that + 1 2 is on a single line. If one enters more than one expression to a single prompt, possibly on/spanning multiple lines, each will be executed.

> but I don't see much gain

It looks better. Much better.

Minus: the command now has spaces in its name, which makes it more difficult to use in scripts.

>> but I don't see much gain

> It looks better. Much better.

I think it is just preference.

I don't think it would be difficult to implement in Emacs, by just transforming the symbol name and presenting that to user instead. I think the read-extended-command-1 is the place where they actually do the work. They could also store a display string for each command in symbols plist as they do with interactive form, but it would be more surgery and as you say harder to use in the code. If display string is decoupled from the function name than the programmer has to remember as well the name for the command, but if they just do a transformation than the programmer can remember the rule. We are used to this in menus and gui stuff like that indeed, labels are often different strings than actual symbol names used for function callbacks, but I am not sure if we would prefer that on the command line.

In my opinion there is still discrepancy between the spoken language and the function names. I guess that is why people have come up with llamas and what not they call those AI llms and chatgpt and so on. I personally am not so fun of using spoken languages as a programming language or a way to control the computer, but who knows, perhaps one day M-x will run some llm search instead of precise lisp function names.

Interlisp for example used a spellchecker for its Lisp. See DWIM (Do What I Mean). Chapter 15: https://larrymasinter.net/86-interlisp-manual-opt.pdf

In Genera the command "Find Symbol" has com-find-symbol as a symbol name. For display it removes the com and the hyphens.

That was an ambitious error recovery in Interlisp indeed. It took like 30 ~ 40 years to get similar thing in Emacs, and we still don't have the "trusted" mode, just cautious with flycheck & co.

> For display it removes the com and the hyphens.

In Emacs, packages are supposed to define a group node and a prefix for symbol names for Customize. Not all packages do, but most of quality ones do. We could actually use that prefix and implement similar strategy to display labels for menus and commands. Menus in Emacs are also implemented as keymaps, but they do require a programmer to specify a label for display in "easy menu" as they call their menu implementation. This strategy could thus remove the need for that extra label.

DWIM from Interlisp could be implemented in forms too. All forms have to use known symbols unless in some well-defined places: literals (strings, quoted symbols), the symbol name which is the word after the certain operator (defun, defmacro, defalias, etc), in argument lists, or as a first symbol of locally defining symbols (let, let*, flet, labels and similar). But there are some questions I am not sure how to answer: I think I will have to tell the system somehow that certain part of an expression is a "defining" part so it understands which symbols are to be introduced into the system and not checked or mistaken for misspelled.

It would be actually useful to have such feature, bound to space and return, so when we type it just replaces misspelled symbols. I am a master of misspellings, I often replace two characters place for some reason, like in Siebel as seen :).

> they can't distinguish between calling (foo 1 (+ 1 2) (+ 3 4)) and calling (foo 1) (+ 1 2) (+ 3 4).

The former is encoded as

  > foo 1 (+ 1 2) (+ 3 4)

and the latter is three separate top-level forms, encoded as

  > foo 1

  > + 1 2

  > + 3 4

Here it looks as if I'm assuming we have one-liners, but that doesn't have to be so; there could be a way to insert soft line breaks that don't dispatch the expression:

  > foo 1
        (+ 1 2)
        (+ 3 4)

  > foo 1

  > + 1
      2

  > + 3
      4

You do have to restrict the input to one form. Whereas a REPL which uses regular notation can handle a single input line of (foo 1) (+ 1 2), and do two evaluations, we cannot have that here. This style of REPL basically inserts parentheses for you, and it inserts one set of them around your whole input, which makes it a single form.

Yes, well that is basically what I meant. I guess in practice, those examples I made are contrived, so I suppose what they do is not a problem for the most people in practice, so I don't think it is a big argument against.

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