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TS: `integer?' vs `Integer' #184

Open racket-bug-submit opened 9 years ago

racket-bug-submit commented 9 years ago
Originally submitted by Eli Barzilay on: Sat Feb 06 23:08:01 -0500 2010

Enter the program below, then be surprised. (I don't see any point in making Integer' be what it is in other statically typed languages, wheninteger?' means something different.)

Steps to Reproduce:
#lang typed-scheme
(: foo : Any -> Integer)
(define (foo x)
  (if (integer? x)
      x
      1))
Release:
4.2.4
Environment:
unix "Linux winooski.ccs.neu.edu 2.6.23.17-88.fc7 #1 SMP Thu May 15 00:02:29 EDT 2008
 x86_64 x86_64 x86_64 GNU/Linux" (x86_64-linux/3m) (get-display-depth) = 16
Human Language: english
(current-memory-use) 176532328

Collections:
(("/home/eli/.plt-scheme/4.2.4/collects" "info-domain" "pl") ("/home/eli/plt/collects"
 "icons" "ffi" "mred" "dynext" "mzscheme" "make" "preprocessor" "file" "openssl" "sgl"
 "scriblib" "s-exp" "slideshow" "mysterx" "graphics" "test-engine" "scheme" "frtime"
 "wxme" "lazy" "mzlib" "macro-debugger" "scribble" "syntax-color" "mzcom" "help" "swindle"
 "config" "net" "hierlist" "test-box-recovery" "2htdp" "profile" "trace" "mrlib" "algol60"
 "browser" "framework" "typed-scheme" "at-exp" "info-domain" "compiler" "errortrace"
 "eopl" "syntax" "combinator-parser" "string-constants" "html" "slatex" "stepper"
 "launcher" "unstable" "htdp" "lang" "rnrs" "setup" "deinprogramm" "plot" "teachpack"
 "xml" "scribblings" "planet" "readline" "parser-tools" "embedded-gui" "drscheme"
 "defaults" "srfi" "afm" "r6rs" "version" "typed" "texpict" "games" "tex2page"
 "gui-debugger" "web-server" "r5rs" "redex"))
Computer Language: (("Module") (#(#t write mixed-fraction-e #f #t debug) (default) #()
 "#lang scheme\n" #t))
This bug was converted from Gnats bug 10740.

[anon-submit; eli at barzilay dot org]

mfelleisen commented 9 years ago
On Sun, 7 Feb 2010 12:32:47 -0500, matthias at ccs dot neu dot edu wrote:

Agreed. We need to figure out our numbers

On Feb 6, 2010, at 11:08 PM, eli@barzilay.org wrote:

> A new problem report is waiting at
>  http://bugs.plt-scheme.org/query/?cmd=view&pr=10740
> 
> Reported by Eli Barzilay for release: 4.2.4
> 
> *** Description:
> Enter the program below, then be surprised.
> (I don't see any point in making `Integer' be what it is in other
> statically typed languages, when `integer?' means something different.)
> 
> *** How to repeat:
> #lang typed-scheme
> (: foo : Any -> Integer)
> (define (foo x)
>  (if (integer? x)
>      x
>      1))
> 
> *** Environment:
> unix "Linux winooski.ccs.neu.edu 2.6.23.17-88.fc7 #1 SMP Thu May 15 00:02:29 EDT 2008 x86_64 x86_64 x86_64 GNU/Linux" (x86_64-linux/3m) (get-display-depth) = 16
> Human Language: english
> (current-memory-use) 176532328
> 
> Collections:
> (("/home/eli/.plt-scheme/4.2.4/collects" "info-domain" "pl") ("/home/eli/plt/collects" "icons" "ffi" "mred" "dynext" "mzscheme" "make" "preprocessor" "file" "openssl" "sgl" "scriblib" "s-exp" "slideshow" "mysterx" "graphics" "test-engine" "scheme" "frtime" "wxme" "lazy" "mzlib" "macro-debugger" "scribble" "syntax-color" "mzcom" "help" "swindle" "config" "net" "hierlist" "test-box-recovery" "2htdp" "profile" "trace" "mrlib" "algol60" "browser" "framework" "typed-scheme" "at-exp" "info-domain" "compiler" "errortrace" "eopl" "syntax" "combinator-parser" "string-constants" "html" "slatex" "stepper" "launcher" "unstable" "htdp" "lang" "rnrs" "setup" "deinprogramm" "plot" "teachpack" "xml" "scribblings" "planet" "readline" "parser-tools" "embedded-gui" "drscheme" "defaults" "srfi" "afm" "r6rs" "version" "typed" "texpict" "games" "tex2page" "gui-debugger" "web-server" "r5rs" "redex"))
> Computer Language: (("Module") (#(#t write mixed-fraction-e #f #t debug) (default) #() "#lang scheme\n" #t))
>
carl-eastlund commented 9 years ago
On Sun, 7 Feb 2010 12:40:22 -0500, cce at plt-scheme dot org wrote:

This design is an intentional tradeoff; as nice as it would be to have integer? correspond with Integer, the set of exact-or-inexact integers does not have many operations closed over it. Arithmetic with inexact integers can result in non-integer results, so +, -, and * could no longer have the types "Integer* -> Integer". In order to make Integer a useful and sound type, it needs to be exact only. The options are then to make exact-integer? the predicate, or to replace integer? with exact-integer? in Typed Scheme, which changes its behavior from Scheme.

[Paraphrasing from conversations with Sam]

Carl Eastlund

On Sun, Feb 7, 2010 at 12:32 PM, Matthias Felleisen matthias@ccs.neu.edu wrote:

Agreed. We need to figure out our numbers

On Feb 6, 2010, at 11:08 PM, eli@barzilay.org wrote:

A new problem report is waiting at =A0http://bugs.plt-scheme.org/query/?cmd=3Dview&pr=3D10740

Reported by Eli Barzilay for release: 4.2.4

*\ Description: Enter the program below, then be surprised. (I don't see any point in making Integer' be what it is in other statically typed languages, wheninteger?' means something different.)

racket-bug-submit commented 9 years ago
On Sun, 7 Feb 2010 12:43:46 -0500, eli at barzilay dot org wrote:

FWIW, the current situation is pretty bad. The fake number?' thing tricky to get over, and this lack of someExactInteger' thing seems like trouble. I can see how a proper Integer' is problematic, in the sense that people don't get what they expect, but that's the same thing that happens withinteger?' so it's shouldn't be TS's business to fix it...

(And FWIW_1, I never liked the fact that (integer? 3.0) returns true -- it's a constant surprise, it messes up code with adding more tests, and I don't get the sense for it -- since 3.0 could be some approximation like any other flonum. I wouldn't miss this feature if it went away, but it's probably too late...)

On Feb 7, Matthias Felleisen wrote:

Agreed. We need to figure out our numbers

On Feb 6, 2010, at 11:08 PM, eli@barzilay.org wrote:

A new problem report is waiting at http://bugs.plt-scheme.org/query/?cmd=view&pr=10740

Reported by Eli Barzilay for release: 4.2.4

*\ Description: Enter the program below, then be surprised. (I don't see any point in making Integer' be what it is in other statically typed languages, wheninteger?' means something different.)

*\ How to repeat:

lang typed-scheme

(: foo : Any -> Integer) (define (foo x) (if (integer? x) x 1))

      ((lambda (x) (x x)) (lambda (x) (x x)))          Eli Barzilay:
                http://barzilay.org/                   Maze is Life!
carl-eastlund commented 9 years ago
On Sun, 7 Feb 2010 12:48:00 -0500, cce at plt-scheme dot org wrote:

Sam may not have made an announcement yet, this may be still a feature in development, but "typed-scheme" is essentially a legacy language -- hence the "number?" hack to keep old code working, because Sam accidentally made Number mean Real instead of Complex.

If you use "#lang typed/scheme" instead (note the slash), number? means number? and Number means Complex. The language with the slash in it is the "future of Typed Scheme". I've been adapting my typed code to it, for instance.

Carl Eastlund

On Sun, Feb 7, 2010 at 12:43 PM, Eli Barzilay <eli@barzilay.org> wrote:
> FWIW, the current situation is pretty bad. =A0The fake `number?' thing
> tricky to get over, and this lack of some `ExactInteger' thing seems
> like trouble. =A0I can see how a proper `Integer' is problematic, in the
> sense that people don't get what they expect, but that's the same
> thing that happens with `integer?' so it's shouldn't be TS's business
> to fix it...
>
> (And FWIW_1, I never liked the fact that (integer? 3.0) returns true
> -- it's a constant surprise, it messes up code with adding more tests,
> and I don't get the sense for it -- since 3.0 could be some
> approximation like any other flonum. =A0I wouldn't miss this feature if
> it went away, but it's probably too late...)
>
>
> On Feb =A07, Matthias Felleisen wrote:
>> Agreed. We need to figure out our numbers
>>
>>
>> On Feb 6, 2010, at 11:08 PM, eli@barzilay.org wrote:
>>
>> > A new problem report is waiting at
>> > =A0http://bugs.plt-scheme.org/query/?cmd=3Dview&pr=3D10740
>> >
>> > Reported by Eli Barzilay for release: 4.2.4
>> >
>> > *** Description:
>> > Enter the program below, then be surprised.
>> > (I don't see any point in making `Integer' be what it is in other
>> > statically typed languages, when `integer?' means something different.=
)
>> >
>> > *** How to repeat:
>> > #lang typed-scheme
>> > (: foo : Any -> Integer)
>> > (define (foo x)
>> > =A0(if (integer? x)
>> > =A0 =A0 =A0x
>> > =A0 =A0 =A01))
>
> --
> =A0 =A0 =A0 =A0 =A0((lambda (x) (x x)) (lambda (x) (x x))) =A0 =A0 =A0 =
=A0 =A0Eli Barzilay:
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0http://barzilay.org/ =A0 =A0 =A0 =
=A0 =A0 =A0 =A0 =A0 =A0 Maze is Life!
>
racket-bug-submit commented 9 years ago
On Sun, 7 Feb 2010 12:50:09 -0500, eli at barzilay dot org wrote:

On Feb 7, Carl Eastlund wrote:

This design is an intentional tradeoff; as nice as it would be to have integer? correspond with Integer,

I don't consider it a tradeoff from the typed scheme POV: `integer?' is what it is, and TS should follow that. Any attempts to "fix" it are going to create very bad confusions, as is the current state. It would be semi-excusable if TS couldn't follow that, but one of its main points is that it can.

the set of exact-or-inexact integers does not have many operations closed over it. Arithmetic with inexact integers can result in non-integer results, so +, -, and * could no longer have the types "Integer* -> Integer". In order to make Integer a useful and sound type, it needs to be exact only.

Right -- Integer' is not too useful, just likeinteger?'.

The options are then to make exact-integer? the predicate, or to replace integer? with exact-integer? in Typed Scheme, which changes its behavior from Scheme.

Doing that in TS would be a very bad idea.

-- ((lambda (x) (x x)) (lambda (x) (x x))) Eli Barzilay: http://barzilay.org/ Maze is Life!

racket-bug-submit commented 9 years ago
On Sun, 7 Feb 2010 12:52:16 -0500, eli at barzilay dot org wrote:

On Feb 7, Carl Eastlund wrote:

Sam may not have made an announcement yet, this may be still a feature in development, but "typed-scheme" is essentially a legacy language -- hence the "number?" hack to keep old code working, because Sam accidentally made Number mean Real instead of Complex.

If you use "#lang typed/scheme" instead (note the slash), number? means number? and Number means Complex. The language with the slash in it is the "future of Typed Scheme". I've been adapting my typed code to it, for instance.

(I'm not using TS in any such way.  The thing that was a problem for
me is that there is a new "typed-scheme/private/base-env-numeric.ss".)

-- ((lambda (x) (x x)) (lambda (x) (x x))) Eli Barzilay: http://barzilay.org/ Maze is Life!

carl-eastlund commented 9 years ago
On Sun, 7 Feb 2010 13:04:56 -0500, cce at plt-scheme dot org wrote:

Ah, you want the type to be called ExactInteger so that the misunderstanding gets corrected when someone types Integer. Personally, I like the brevity of typing Integer, but now I get your implication. I'll let Sam take it from here. :)

Carl Eastlund

On Sun, Feb 7, 2010 at 12:50 PM, Eli Barzilay eli@barzilay.org wrote:

On Feb =A07, Carl Eastlund wrote:

This design is an intentional tradeoff; as nice as it would be to have integer? correspond with Integer,

I don't consider it a tradeoff from the typed scheme POV: `integer?' is what it is, and TS should follow that. =A0Any attempts to "fix" it are going to create very bad confusions, as is the current state. =A0It would be semi-excusable if TS couldn't follow that, but one of its main points is that it can.

the set of exact-or-inexact integers does not have many operations closed over it. =A0Arithmetic with inexact integers can result in non-integer results, so +, -, and * could no longer have the types "Integer* -> Integer". =A0In order to make Integer a useful and sound type, it needs to be exact only.

Right -- Integer' is not too useful, just likeinteger?'.

The options are then to make exact-integer? the predicate, or to replace integer? with exact-integer? in Typed Scheme, which changes its behavior from Scheme.

Doing that in TS would be a very bad idea.

=A0 =A0 =A0 =A0 =A0((lambda (x) (x x)) (lambda (x) (x x))) =A0 =A0 =A0 = =A0 =A0Eli Barzilay: =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0http://barzilay.org/ =A0 =A0 =A0 = =A0 =A0 =A0 =A0 =A0 =A0 Maze is Life!

racket-bug-submit commented 9 years ago
On Sun, 7 Feb 2010 13:12:10 -0500, eli at barzilay dot org wrote:

On Feb 7, Carl Eastlund wrote:

Ah, you want the type to be called ExactInteger so that the misunderstanding gets corrected when someone types Integer. Personally, I like the brevity of typing Integer, but now I get your implication. I'll let Sam take it from here. :)

  • Yes, `ExactInteger' would be better.
  • I also like the shorter `Integer' -- but this is minor to the confused result that follows.
  • The fact that this is more of a problem in TS than it is in plain scheme is, IMO, just an indicator that people tend to use integer?' in many places where they should really be usingexact-integer?'. (Or an `and' expression before that was added.)
  • Perhaps something like `EInteger' would work better as a short name, but it will still be something that would surprise people. The good thing is that this will be caught by the checker, instead of as some unexpected runtime error.
  • And finally -- if it is at all practical, then what I said is that I'd vote for `integer?' changing at the core language level. It's something that I never liked. (In fact, I think that this was one of the first things that annoyed me when I switched to plt.)

      ((lambda (x) (x x)) (lambda (x) (x x)))          Eli Barzilay:
                http://barzilay.org/                   Maze is Life!
mfelleisen commented 9 years ago
On Sun, 7 Feb 2010 13:31:41 -0500, matthias at ccs dot neu dot edu wrote:

In addition we need to make sure that the semantics of our modules stays what Untyped Racketeers expect.

On Feb 7, 2010, at 12:40 PM, Carl Eastlund wrote:

This design is an intentional tradeoff; as nice as it would be to have integer? correspond with Integer, the set of exact-or-inexact integers does not have many operations closed over it. Arithmetic with inexact integers can result in non-integer results, so +, -, and * could no longer have the types "Integer* -> Integer". In order to make Integer a useful and sound type, it needs to be exact only. The options are then to make exact-integer? the predicate, or to replace integer? with exact-integer? in Typed Scheme, which changes its behavior from Scheme.

[Paraphrasing from conversations with Sam]

Carl Eastlund

On Sun, Feb 7, 2010 at 12:32 PM, Matthias Felleisen matthias@ccs.neu.edu wrote:

Agreed. We need to figure out our numbers

On Feb 6, 2010, at 11:08 PM, eli@barzilay.org wrote:

A new problem report is waiting at http://bugs.plt-scheme.org/query/?cmd=view&pr=10740

Reported by Eli Barzilay for release: 4.2.4

*\ Description: Enter the program below, then be surprised. (I don't see any point in making Integer' be what it is in other statically typed languages, wheninteger?' means something different.)

mfelleisen commented 9 years ago
On Sun, 7 Feb 2010 13:34:38 -0500, matthias at ccs dot neu dot edu wrote:
  1. Let's use Entire instead of ExactInteger.
  2. We could divorce our Untyped semantics from that of Scheme.

I guess I am agreeing with Eli.

On Feb 7, 2010, at 1:12 PM, Eli Barzilay wrote:

On Feb 7, Carl Eastlund wrote:

Ah, you want the type to be called ExactInteger so that the misunderstanding gets corrected when someone types Integer. Personally, I like the brevity of typing Integer, but now I get your implication. I'll let Sam take it from here. :)

  • Yes, `ExactInteger' would be better.
  • I also like the shorter `Integer' -- but this is minor to the confused result that follows.
  • The fact that this is more of a problem in TS than it is in plain scheme is, IMO, just an indicator that people tend to use integer?' in many places where they should really be usingexact-integer?'. (Or an `and' expression before that was added.)
  • Perhaps something like `EInteger' would work better as a short name, but it will still be something that would surprise people. The good thing is that this will be caught by the checker, instead of as some unexpected runtime error.
  • And finally -- if it is at all practical, then what I said is that I'd vote for `integer?' changing at the core language level. It's something that I never liked. (In fact, I think that this was one of the first things that annoyed me when I switched to plt.)

     ((lambda (x) (x x)) (lambda (x) (x x)))          Eli Barzilay:
               http://barzilay.org/                   Maze is Life!
racket-bug-submit commented 9 years ago
On Sun, 7 Feb 2010 13:38:10 -0500, eli at barzilay dot org wrote:

On Feb 7, Matthias Felleisen wrote:

  1. Let's use Entire instead of ExactInteger.
  2. We could divorce our Untyped semantics from that of Scheme.

I guess I am agreeing with Eli.

I'm not sure -- I would prefer it if (untyped) scheme changes... (But in any case, having `typed/scheme' as a language won't make much sense if it's a different language.)

-- ((lambda (x) (x x)) (lambda (x) (x x))) Eli Barzilay: http://barzilay.org/ Maze is Life!

racket-bug-submit commented 9 years ago
On Sun, 7 Feb 2010 13:50:55 -0500, eli at barzilay dot org wrote:

More fun:

    > (odd? 1.0)
    #t
    > (odd? 1.2)
    odd?: expects argument of type <integer>; given 1.2

So now you have integer?',', and `Integer?' do deal with.

    > denominator
    - : (Number -> Integer)
    #<procedure:denominator>
    > (denominator 2.0)
    - : Integer
    1.0
    > (quotient 3.0 2)
    Type Checker: Expected Integer, but got Float in: 3.0

This works in plain scheme. The mistake here and in the previous thing is that they seem to be based on translations of <integer>' toInteger', which is invalid with the current state of things.

Another suggestion:

More points:

    [integer? (Univ . -> . B : (-LFS (list (-filter (Un -Integer -Flonum)))
                                     (list (-not-filter -Integer))))]
    [exact-integer? (make-pred-ty -Integer)]

  (As an experiment: trying to explain it.)  Doing what I think it
  should do would make the TS code that makes these definitions much
  simpler.
rfindler commented 9 years ago
On Sun, 7 Feb 2010 13:00:17 -0600, robby at eecs dot northwestern dot edu wrote:

I'm late to the party, but I agree that TS is not the place to patch over things disliked about the Scheme number system. If there were another language with a different numeric tower where someone thought it thru and came to different conclusions about (integer? 3.0), for example, then we could have a different typed language for that one that might have Integer that didn't contain 3.0. But until we do, Typed Scheme is Typed Scheme not "Typed something very close to Scheme"

My $0.02.

Robby

samth commented 9 years ago
On Mon, 8 Feb 2010 12:58:52 -0500, samth at ccs dot neu dot edu wrote:

There are several issues here, some hard, some easy, and some naming disputes:

  1. Should `integer?' in Typed Scheme mean the same thing as in untyped Scheme. Yes, everyone agrees on this, and it is the current behavior.
  2. Should there be a type which corresponds to the inexact integers? Since untyped Scheme has them, probably Typed Scheme should too.
  3. What should these different types be called? Here, I prefer making the useful type the convenient one, but I see the argument on the other side as well. I'm undecided here.
  4. Should the semantics of `integer?' change everywhere to eliminate the concept of inexact integers? Mostly, I'd say yes, but I haven't thought about this that hard, nor about what compatibility problems this would cause. This isn't really a Typed Scheme question.
  5. Should I fix `denominator'? Yes. Fixed in SVN very soon.

On Sun, Feb 7, 2010 at 1:50 PM, Eli Barzilay eli@barzilay.org wrote:

  • More than that -- doing that would probably be very productive in  the find-bugs-in-untyped-code department that Sam likes so much.  The current mess is almost as if he's trying hard to twist things so  these bugs are not bugs.

Which bugs are not bugs because of these choices? If anything, too many correct programs are being statically rejected. -- sam th samth@ccs.neu.edu

rfindler commented 9 years ago
On Mon, 8 Feb 2010 12:01:32 -0600, robby at eecs dot northwestern dot edu wrote:

For 3: I'd vote to make the names match the predicates that are in Scheme, as I see this as being like bullet 4.

Robby

On Mon, Feb 8, 2010 at 11:58 AM, Sam Tobin-Hochstadt samth@ccs.neu.edu wr= ote:

There are several issues here, some hard, some easy, and some naming disp= utes:

  1. Should `integer?' in Typed Scheme mean the same thing as in untyped Scheme. =C2=A0Yes, everyone agrees on this, and it is the current behavio= r.
  2. Should there be a type which corresponds to the inexact integers? Since untyped Scheme has them, probably Typed Scheme should too.
  3. What should these different types be called? =C2=A0Here, I prefer maki= ng the useful type the convenient one, but I see the argument on the other side as well. =C2=A0I'm undecided here.
  4. Should the semantics of `integer?' change everywhere to eliminate the concept of inexact integers? =C2=A0Mostly, I'd say yes, but I haven't thought about this that hard, nor about what compatibility problems this would cause. =C2=A0This isn't really a Typed Scheme question.
  5. Should I fix `denominator'? Yes. =C2=A0Fixed in SVN very soon.

On Sun, Feb 7, 2010 at 1:50 PM, Eli Barzilay eli@barzilay.org wrote:

  • More than that -- doing that would probably be very productive in =C2=A0the find-bugs-in-untyped-code department that Sam likes so much. =C2=A0The current mess is almost as if he's trying hard to twist things = so =C2=A0these bugs are not bugs.

Which bugs are not bugs because of these choices? If anything, too

many correct programs are being statically rejected.

sam th samth@ccs.neu.edu