SimpleIO in JEP draft 8323335
Tagir Valeev
amaembo at gmail.com
Tue Feb 20 14:47:08 UTC 2024
I guess, this is not about "give me more" but about "design a thing that
will be really useful". If SimpleIO will not be satisfactory for solving
90% of student problems, then probably there's no point in introducing it
at all? Surely, one should draw a line somewhere, but it looks like if the
purpose of the new API is to easen the learning of Java, then an ability to
input numbers should be there.
Teaching Integer::parseInt or new Scanner() sounds contradicting to the
idea of hiding irrelevant details like classes and static methods from the
students until they need them. Because you'll need to explain what is
Integer and what is parseInt. Or probably you can say "don't care now, just
write it this way, we'll cover this later". But is it much different from
public static void main? Why did we start all of this in the first place?
When I was a child, I learned BASIC, and I remember that one could ask a
number from a user typing simply INPUT X. The concept of string variables
like X$ was introduced much later, so in my mind it was completely ok that
we can ask for a number, without an intermediate step like ask for a
string, then convert it to the number. Not sure if it was
pedagogically correct but it certainly simplified my first steps in
computer programming (well, paper programming in fact, as I had no
computer).
With best regards,
Tagir Valeev.
On Tue, Feb 20, 2024 at 3:34 PM Brian Goetz <brian.goetz at oracle.com> wrote:
> What you're really saying is "I want more than you're giving me." And
> there's nothing wrong with wanting more. You seem to have mostly accepted
> that the primitive is "read a line of input as a string", but it leaves you
> with a problem: you don't want to read strings, you want to read numbers.
> That's all fine.
>
> But the flip side of "this isn't good enough, give us more" is that if
> there isn't a "more" that is good enough to meet the the bar, you're going
> to get ... nothing. It's a foundational design principle for Java (thanks
> James!) that if you don't know the right thing to do, then don't do
> anything (yet). The alternatives that have been proposed (all of which we
> already went through before they came around again here) did not meet the
> bar. This is what meets the bar. It may not be as much as you want, but
> it is something, and it combines with all the other possible next steps.
>
> As a teacher, you have many choices. You can keep doing what you've been
> doing, teaching Scanner; many teachers will. Or you could distribute your
> own library of convenience methods -- many teachers do. Or you could teach
> Integer::parseInt, which is messy, but has the benefit of being exactly as
> messy as the problem is -- which is also a useful lesson. Or, or, or, or.
>
> And if you don't like the magic static import, don't use it! Tell your
> students to use `SimpleIO::readAStringPlease`. We are not trying to create
> a beginners dialect here.
>
> All of this is to say: we are not trying to put out a One True Only Way To
> Teach Java. We're smoothing out the path in a way that admits many
> teaching paths, including ignoring all this stuff. Is there more that
> could be done? Of course. And when we have a *good* candidate for what
> the next hundred feet of onramp looks like, we will proceed. And I am
> confident that it will not conflict with these first hundred feet, because
> -- how could it?
>
>
>
>
>
> On 2/20/2024 6:44 AM, Cay Horstmann wrote:
>
> I am one of the people who writes books for beginners. I have a whole
> bunch of example programs that involve reading numbers. Professors adopting
> my books have a ton of exercises that involve reading numbers. I can't
> ignore reading numbers.
>
> I agree that input and println are reasonable primitives for beginners,
> and that number parsing can be done in a separate step. But if that parsing
> step is not simple for beginners, I don't think input will find much use
> for beginners either.
>
> For my books, I need to decide what to do in the (n + 1)st edition. Should
> I stick with
>
> Scanner in = new Scanner(System.in);
> ...
> System.out.print("How old are you? ");
> int age = in.nextInt();
>
> or switch to
>
> println("How old are you?");
> int age = in.nextInt();
>
> or go all the way to
>
> int age = Integer.parseInt(input("How old are you"));
>
> I have no conceptual problem with in.nextInt(). I need to explain method
> calls early on, so that students can work with strings.
>
> With the new way, I have a different problem. Now I need to explain to
> students that they can call an unqualified input, but parseInt needs to be
> qualified. And I have to accelerate the coverage of static methods.
>
> As Brian says, there are too many conflicting goals.
>
> If the goal is simplicity and consistency, it would be more useful not to
> use a magic static import. If SimpleIO.input is too long, it could be
> IO.in, with IO in java.lang.
>
> If the goal is convenience, it would be better to have more magically
> statically imported methods, in particular parseInt, parseDouble. Or
> readAnInt, readADouble...
>
> Cheers,
>
> Cay
>
>
> On 19/02/2024 18.06, Brian Goetz wrote:
>
> There's a reason there are so many opinions here: because the goals are in
> conflict. Everyone wants simplicity, but people don't agree on what
> "simple" means. (Cue the jokes about "I would simply not write programs
> with bugs.")
>
> Yes, getting numbers from the user is a basic task. But it is not, in any
> way, simple! Because reading numbers from the input is invariably
> complected with discarding things that are "acceptably non-numbery" (e.g.,
> whitespace), which is neither simple nor usually terribly well documented.
> We've all encountered the problem in many language runtimes where reading a
> number using the "friendly way" leaves the input in a state that requires
> fixing or yields surprises for the next operation.
>
> This is because reading a number from an input stream is not any sort of
> primitive; it is the composite of reading from the input, deciding what to
> skip, deciding when to stop reading, converting to another type, deciding
> what state to leave the input stream in, and deciding what to do if no
> number could be found (or if the number was too big to fit into an int,
> etc.) This is not^3 simple!
>
> C starts with a simple and principled answer, which is that the IO
> primitive is getchar() and putchar(). Reading or writing one character is
> unquestionably a primitive. (But also, unless you are writing `cat`, no
> one wants to program with getchar and putchar, because it's too primitive.)
>
> One can make a reasonable case for "write a line / read a line" being
> sensible primitives. They are simple enough: no parsing, no deciding what
> to throw away, no possible errors other than EOF, it is clear what state
> you leave the stream in. These may not be what the student wants, but they
> are primitives a student can deal with without having to understand parsing
> and error handling and statefulness yet.
>
> String s = getALine();
> printALine(s);
>
> is a program every student can reason about.
>
> But, it is true that dealing in strings, while honest and simple, is not
> always what the student wants. But herein lies the strongest argument for
> not trying to reinvent Scanner here: the ability to read numbers makes the
> complexity of the problem, and hence of the API, much much bigger.
> (Scanner was very well intentioned, and was not written by children, and
> yet none of us want to use it. That's a sign that a one-size-fits-all
> magic input processing system is harder than it looks, and for something
> that is explicitly aimed at beginners, is a double warning sign.)
>
> I could imagine someone suggesting "why don't you just add
> `readLineAsInt`". But what would happen next? Well, there would be a
> million requests (including from folks like Cay) of "you should add X", and
> then the result is a mishmash jumble of an API (that's already terrible),
> but worse, it's an onramp that leads to nowhere. Once the user's needs are
> slightly more complicated, they are nowhere.
>
> Remi has it absolutely right (yes, I really said that) with
>
> The classical program is:
> input -> strings -> objects -> strings -> output
>
>
> We do not do users a favor by blurring the distinction between "input ->
> string" and "string -> object", and because the latter is so much more
> open-ended than the former, the latter infects the former with its
> complexity if we try.
>
> Is this simple API the most wonderful, be-all of APIs? Of course not.
> But it is a sensible set of primitives that users can understand and *build
> on* in a transparent way.
>
> Some teachers may immediately reach for teaching Integer::parseInt; that's
> a reasonable strategy, it exposes students to the questions of "what
> happens when preconditions fail", and the two compose just fine. But maybe
> you don't like Integer::parseInt for some reason. Another way to teach
> this is to have them write it themselves. This will expose them to all
> sorts of interesting questions (what about whitespace? what about double
> negatives?), but of course is also throwing in the deep end of the pool.
> But SimpleIO::readMeALinePlease is agnostic; it works with both approaches.
>
> Could the JDK use some better tools for parsing? Sure; pattern matching
> has a role to play here, a `String::unformat` would be really cool, and I
> love parser combinators. All of this can happen in the future, and none
> have the effect of making this API look like yet another white elephant
> like Scanner. Because it focused purely on the basics.
>
>
> On 2/19/2024 7:25 AM, Remi Forax wrote:
>
> I agree with Brian here,
> as a teacher, you have to talk about parsing and formatting, those should
> not be hidden.
>
> The classical program is:
> input -> strings -> objects -> strings -> output
>
> Rémi
>
> ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
>
> *From: *"Tagir Valeev" <amaembo at gmail.com> <amaembo at gmail.com>
> *To: *"Cay Horstmann" <cay at horstmann.com> <cay at horstmann.com>
> *Cc: *"Brian Goetz" <brian.goetz at oracle.com> <brian.goetz at oracle.com>,
> "amber-dev" <amber-dev at openjdk.org> <amber-dev at openjdk.org>
> *Sent: *Monday, February 19, 2024 10:09:35 AM
> *Subject: *Re: SimpleIO in JEP draft 8323335
>
> I agree that simple methods to get numeric input are essential for
> beginners. They should not be distracted with a complex ceremony. Instead,
> they should be able to learn control flow statements and simple algorithms
> as soon as possible, having a simple way to get numbers from the user.
> With best regards,
> Tagir Valeev.
>
> On Mon, Feb 19, 2024 at 9:10 AM Cay Horstmann <cay at horstmann.com>
> <cay at horstmann.com> wrote:
>
> Yes, that's what I am saying. If scanners live in vain, stick with
> a subset of the Console methods. Use its readLine. Make it so that SimpleIO
> uses System.console(). And add print and println to Console.
>
> The JEP talks about being able to start programming without having
> to know about static methods. How does a beginner read a number? With
> Integer.parseInt(readLine(prompt))?
>
> What about locales? Is print/println localized? Console.printf is.
> If so, how are beginners from around the world supposed to read localized
> numbers? With NumberFormat.getInstance().parse(readLine(prompt))?
>
> Adding localized readInt/readDouble to SimpleIO might do the
> trick. Do they consume the trailing newline? (The equivalent Scanner
> methods don't, which is definitely a sharp edge for beginners.)
>
> On 18/02/2024 23.08, Brian Goetz wrote:
> > OK, so is this really just that that you are bikeshedding the
> name? Renaming `input` to `readLine`?
> >
> > This is a perfectly reasonable naming choice, of course, but
> also, not what you suggested the first time around:
> >
> > > ... "a third API" ...
> >
> > > ... "there are two feasible directions" ...
> >
> > So what exactly are you suggesting?
> >
> >
> >
> > On 2/18/2024 5:03 PM, Cay Horstmann wrote:
> >> Like I said, either the scanner methods or the console methods
> are fine.
> >>
> >> I am of course aware of the utility/complexity of Scanner, and
> can understand the motivation to have a simpler/feebler behavior in
> SimpleIO. Like the one in Console.
> >>
> >> You don't have to "get a console". A SimpleIO.readLine method
> can just invoke readLine on the system console.
> >>
> >> My objection is to add yet another "input" method into the mix.
> "input" is weak. Does it read a token or the entire line? Does it consume
> the newline? And if it does just what readLine does, why another method
> name? Because "input" is three characters fewer? Let's not count
> characters.
> >>
> >> On 18/02/2024 22.43, Brian Goetz wrote:
> >>> I think you are counting characters and not counting concepts.
> >>>
> >>> Scanner has a ton of complexity in it that can easily trip up
> beginners. The main sin (though there are others) is that input and
> parsing are complected (e.g., nextInt), which only causes more problems
> (e.g., end of line issues.) Reading from the console is clearly a () ->
> String operation. The input() method does one thing, which is get a line
> of text. That's simple.
> >>>
> >>> Integer.parseInt (or, soon, patterns that match against string
> and bind an int) also does one thing: convert a string from int. It may
> seem verbose to have to do both explicitly, but it allows each of these
> operations to be simple, and it is perfectly obvious what is going on. On
> the other hand, Scanner is a world of complexity on its own.
> >>>
> >>> Console::readLine is nice, but first you have to get a
> Console. ("Why can I print something without having to get some magic
> helper object, but I can't do the same for reading?") What we're
> optimizing for here is conceptual simplicity; the simplest possible input
> method is the inverse of println. The fact that input has to be validated
> is a fact of life; we can treat validation separately from IO (and we
> should), and it gets simpler when you do.
> >>>
> >>> On 2/18/2024 4:12 PM, Cay Horstmann wrote:
> >>>> I would like to comment on the simplicity of
> https://openjdk.org/jeps/8323335 for beginning students.
> >>>>
> >>>> I am the author of college texts for introductory
> programming. Like other authors, I introduce the Scanner class (and not
> Console) for reading user input. Given that students already know about
> System.out, it is simpler to call
> >>>>
> >>>> System.out.print("How old are you? ");
> >>>> int x = in.nextInt(); // in is a Scanner
> >>>>
> >>>> than
> >>>>
> >>>> int x = Integer.parseInt(console.readLine("How old are you?
> "));
> >>>>
> >>>> or with the JEP draft:
> >>>>
> >>>> int x = Integer.parseInt(input("How old are you? "));
> >>>>
> >>>> Then again, having a prompt string is nice too, so I could
> imagine using the Console API with Integer.parseInt and Double.parseDouble,
> instead of Scanner.nextInt/nextDouble.
> >>>>
> >>>> But why have a third API, i.e. "input"?
> >>>>
> >>>> I think there are two feasible directions. Either embrace the
> Scanner API and next/nextInt/nextDouble/nextLine, or the Console API and
> readLine. Adding "input" into the mix is just clutter, and ambiguous
> clutter at that. At least readLine makes it clear that the entire line is
> consumed.
> >>>>
> >>>> Cheers,
> >>>>
> >>>> Cay
> >>>>
> >>>> --
> >>>>
> >>>> Cay S. Horstmann |
> https://urldefense.com/v3/__http://horstmann.com__;!!ACWV5N9M2RV99hQ!IuXZk_tqIH8rEw1bD3uYb8UcIZF-nnoeFT3UG17pMO5EVXIYVRaAKi7XCq_T02HwnAek1wuV8Wed08w$
> | mailto:cay at horstmann.com <cay at horstmann.com>
> >>>
> >>
> >
>
> --
> --
>
> Cay S. Horstmann |
> https://urldefense.com/v3/__http://horstmann.com__;!!ACWV5N9M2RV99hQ!JDq2P0DR423V62MvLF-CBrjfMSFshyy9lkQdQQPt5aEojp3WbQriYDtG-00NepYgsFay4aXHAQFHA24$
>
> <https://urldefense.com/v3/__http://horstmann.com__;!!ACWV5N9M2RV99hQ!IZrLgaQxOHBjUURoC5mWbfsijev257bb4C0DMamUDpoGqS5JMACpaMKsbUNQlWcGds7fifmS9sARC6aKMHEf$>
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> | mailto:cay at horstmann.com <cay at horstmann.com>
>
>
>
>
>
>
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