Re: [racket-dev] Oversight in type for path-string?
IMO defining `Path-String' in a way that doesn't correspond to `path-string?' is not a good idea. I'd prefer it if the name was changed or if the type changes to accurately reflect the predicate. (The latter might be more problematic since it probably implies doing more checking than done now, and also there's the question of getting into path-strings for other platforms...) Yesterday, Sam Tobin-Hochstadt wrote: That's true, which is why it has to have a more complex filter than you'd expect. But if a value isn't `path-string?', then it is definitely not a `Path', and if it *is* `path-string?' then it's either a `String' or a `Path'. So we can express an approximation of it's behavior in the type. On Fri, Mar 23, 2012 at 12:09 PM, Eric Dobson eric.n.dob...@gmail.com wrote: Actually I don't think this is an over sight. The null string is a String. And Path-String is Path U String, but (path-string? (string #\null)) = #f. -- ((lambda (x) (x x)) (lambda (x) (x x))) Eli Barzilay: http://barzilay.org/ Maze is Life! _ Racket Developers list: http://lists.racket-lang.org/dev
Re: [racket-dev] Oversight in type for path-string?
On Sat, Mar 24, 2012 at 12:36 PM, Eli Barzilay e...@barzilay.org wrote: IMO defining `Path-String' in a way that doesn't correspond to `path-string?' is not a good idea. I'd prefer it if the name was changed or if the type changes to accurately reflect the predicate. I this this is a place where we just have to accept that types are less precise than runtime checks. The invariant that the string can't contain #\null and that the path must be for the current system is like the invariant that you can't divide by zero. It's not something we can realistically express in the type, and given that `Path-String' is defined to be (U Path String), and is the type used for functions that consume and produce `path-string?' values, I think `Path-String' is the right name. (The latter might be more problematic since it probably implies doing more checking than done now, and also there's the question of getting into path-strings for other platforms...) Yesterday, Sam Tobin-Hochstadt wrote: That's true, which is why it has to have a more complex filter than you'd expect. But if a value isn't `path-string?', then it is definitely not a `Path', and if it *is* `path-string?' then it's either a `String' or a `Path'. So we can express an approximation of it's behavior in the type. On Fri, Mar 23, 2012 at 12:09 PM, Eric Dobson eric.n.dob...@gmail.com wrote: Actually I don't think this is an over sight. The null string is a String. And Path-String is Path U String, but (path-string? (string #\null)) = #f. -- ((lambda (x) (x x)) (lambda (x) (x x))) Eli Barzilay: http://barzilay.org/ Maze is Life! -- sam th sa...@ccs.neu.edu _ Racket Developers list: http://lists.racket-lang.org/dev
Re: [racket-dev] Oversight in type for path-string?
Actually I don't think this is an over sight. The null string is a String. And Path-String is Path U String, but (path-string? (string #\null)) = #f. Sent from a mobile device. On Mar 21, 2012 5:14 PM, John Clements cleme...@brinckerhoff.org wrote: On Mar 21, 2012, at 3:20 PM, Sam Tobin-Hochstadt wrote: On Wed, Mar 21, 2012 at 5:36 PM, John Clements cleme...@brinckerhoff.org wrote: It looks like 'path-string?' is not labeled as a discriminator type. path-string? - : (Any - Boolean) #procedure:path-string? Is this just an oversight? Yes, that's just an oversight, although it's slightly more complicated than you'd think (because `(path-string? (string #\null))' is #f). Well, I just made do with (define-predicate ps? Path-String?), so this certainly isn't a major problem. John _ Racket Developers list: http://lists.racket-lang.org/dev _ Racket Developers list: http://lists.racket-lang.org/dev
Re: [racket-dev] Oversight in type for path-string?
That's true, which is why it has to have a more complex filter than you'd expect. But if a value isn't `path-string?', then it is definitely not a `Path', and if it *is* `path-string?' then it's either a `String' or a `Path'. So we can express an approximation of it's behavior in the type. On Fri, Mar 23, 2012 at 12:09 PM, Eric Dobson eric.n.dob...@gmail.com wrote: Actually I don't think this is an over sight. The null string is a String. And Path-String is Path U String, but (path-string? (string #\null)) = #f. Sent from a mobile device. On Mar 21, 2012 5:14 PM, John Clements cleme...@brinckerhoff.org wrote: On Mar 21, 2012, at 3:20 PM, Sam Tobin-Hochstadt wrote: On Wed, Mar 21, 2012 at 5:36 PM, John Clements cleme...@brinckerhoff.org wrote: It looks like 'path-string?' is not labeled as a discriminator type. path-string? - : (Any - Boolean) #procedure:path-string? Is this just an oversight? Yes, that's just an oversight, although it's slightly more complicated than you'd think (because `(path-string? (string #\null))' is #f). Well, I just made do with (define-predicate ps? Path-String?), so this certainly isn't a major problem. John _ Racket Developers list: http://lists.racket-lang.org/dev -- sam th sa...@ccs.neu.edu _ Racket Developers list: http://lists.racket-lang.org/dev
[racket-dev] Oversight in type for path-string?
It looks like 'path-string?' is not labeled as a discriminator type. path-string? - : (Any - Boolean) #procedure:path-string? Is this just an oversight? John smime.p7s Description: S/MIME cryptographic signature _ Racket Developers list: http://lists.racket-lang.org/dev
Re: [racket-dev] Oversight in type for path-string?
On Wed, Mar 21, 2012 at 5:36 PM, John Clements cleme...@brinckerhoff.org wrote: It looks like 'path-string?' is not labeled as a discriminator type. path-string? - : (Any - Boolean) #procedure:path-string? Is this just an oversight? Yes, that's just an oversight, although it's slightly more complicated than you'd think (because `(path-string? (string #\null))' is #f). -- sam th sa...@ccs.neu.edu _ Racket Developers list: http://lists.racket-lang.org/dev
Re: [racket-dev] Oversight in type for path-string?
On Mar 21, 2012, at 3:20 PM, Sam Tobin-Hochstadt wrote: On Wed, Mar 21, 2012 at 5:36 PM, John Clements cleme...@brinckerhoff.org wrote: It looks like 'path-string?' is not labeled as a discriminator type. path-string? - : (Any - Boolean) #procedure:path-string? Is this just an oversight? Yes, that's just an oversight, although it's slightly more complicated than you'd think (because `(path-string? (string #\null))' is #f). Well, I just made do with (define-predicate ps? Path-String?), so this certainly isn't a major problem. John smime.p7s Description: S/MIME cryptographic signature _ Racket Developers list: http://lists.racket-lang.org/dev
