Re: Ada conference, Ada and Spark
On Fri, Feb 21, 2014 at 12:06 PM, Matej Nanut matejna...@gmail.com wrote: However it might've been nicer if you didn't have to write let mut but just mut. Something similar had been discussed if I recall correctly, and was rejected. Consider: `let (x, mut y) = (1, 2);` which would otherwise have not been possible.
Re: Ada conference, Ada and Spark
On Thursday, 20 February 2014 at 08:03:47 UTC, Paulo Pinto wrote: [cut] I have been following Ada at FOSDEM for the last years, and its use seems to be increasing in Europe for safety critical systems, mainly thanks to C and C++ issues. Maybe this is an area where D could be pushed as well. I don't think so: given that D is C++ done right, it would require many (unlikely to happen) changes to become an interesting alternative for Ada: for example changing the semantic of integers! That said, one question I should ask to Rust devs is why they didn't base Rust on Ada given their goals.. renoX
Re: Ada conference, Ada and Spark
On Friday, 21 February 2014 at 10:01:41 UTC, renoX wrote: On Thursday, 20 February 2014 at 08:03:47 UTC, Paulo Pinto wrote: [cut] I have been following Ada at FOSDEM for the last years, and its use seems to be increasing in Europe for safety critical systems, mainly thanks to C and C++ issues. Maybe this is an area where D could be pushed as well. I don't think so: given that D is C++ done right, it would require many (unlikely to happen) changes to become an interesting alternative for Ada: for example changing the semantic of integers! That said, one question I should ask to Rust devs is why they didn't base Rust on Ada given their goals.. renoX That is easy to answer, I doubt they could with their rule of not having more than 5 characters per keyword. :) -- Paulo
Re: Ada conference, Ada and Spark
On Friday, 21 February 2014 at 12:56:32 UTC, Paulo Pinto wrote: That is easy to answer, I doubt they could with their rule of not having more than 5 characters per keyword. :) Wait, what? REALLY? What kind of rule is that. ahahahha... are they stuck to the 70's? :D
Re: Ada conference, Ada and Spark
On Friday, 21 February 2014 at 13:08:37 UTC, Francesco Cattoglio wrote: On Friday, 21 February 2014 at 12:56:32 UTC, Paulo Pinto wrote: That is easy to answer, I doubt they could with their rule of not having more than 5 characters per keyword. :) Wait, what? REALLY? What kind of rule is that. ahahahha... are they stuck to the 70's? :D Yes really, http://forum.dlang.org/post/glnafbocwjodiwrqw...@forum.dlang.org I just cannot find the Reddit thread any longer.
Re: Ada conference, Ada and Spark
On Friday, 21 February 2014 at 14:27:48 UTC, Paulo Pinto wrote: On Friday, 21 February 2014 at 13:08:37 UTC, Francesco Cattoglio wrote: On Friday, 21 February 2014 at 12:56:32 UTC, Paulo Pinto wrote: That is easy to answer, I doubt they could with their rule of not having more than 5 characters per keyword. :) Wait, what? REALLY? What kind of rule is that. ahahahha... are they stuck to the 70's? :D Yes really, http://forum.dlang.org/post/glnafbocwjodiwrqw...@forum.dlang.org I just cannot find the Reddit thread any longer. That is not true, Rust has several keywords that are more than 5 characters, such as 'continue'. The full list is here: http://static.rust-lang.org/doc/master/rust.html#keywords . It is true that they prefer short keywords over long ones. It used to be the case that 'loop' could mean 'continue' but people found it confusing so it was fixed.
Re: Ada conference, Ada and Spark
On Friday, 21 February 2014 at 17:25:48 UTC, Francesco Cattoglio wrote: On Friday, 21 February 2014 at 15:57:32 UTC, Thiez wrote: That is not true, Rust has several keywords that are more than 5 characters, such as 'continue'. The full list is here: http://static.rust-lang.org/doc/master/rust.html#keywords . It is true that they prefer short keywords over long ones. I knew there was no hard-coded limit, but this try to keep keywords short sounds really stupid to me. No offence to designers, but I really don't think we should save some spar characters in 2014... I do all my coding on a remote SSH, but still I have plenty of screen space to spare ;) My first glance: priv instead of private... bleah! At least it's clear enough mut... what is this? mutable, mutex, perhaps mute? impl could be several different things, too, but I guess it's implements And continue being a different keyword some time ago. In the end they changed it. Tons of discussions and stuff; was it worth saving 3 characters, after all? I hope their standard library is at least WAY more verbose... Otherwise I pity casual Rust programmers :D Depends on how often and where you write those keywords. mut seems to be quite common and even in D I would not like 'reference' more than 'ref', especially since it is used in parameter lists.
Re: Ada conference, Ada and Spark
On Friday, 21 February 2014 at 14:27:48 UTC, Paulo Pinto wrote: On Friday, 21 February 2014 at 13:08:37 UTC, Francesco Cattoglio wrote: On Friday, 21 February 2014 at 12:56:32 UTC, Paulo Pinto wrote: That is easy to answer, I doubt they could with their rule of not having more than 5 characters per keyword. :) Wait, what? REALLY? What kind of rule is that. ahahahha... are they stuck to the 70's? :D Yes really, http://forum.dlang.org/post/glnafbocwjodiwrqw...@forum.dlang.org I just cannot find the Reddit thread any longer. Obviously, there is no rule in Rust that keywords have no more than 5 letters (return, extern, ...) but the designers favor short keywords, maybe a bit much for my taste. OTOH, I prefer their preference for favoring immutability and expression oriented style to D's statement oriented preference. The latest version of Ada tries to fix Ada a bit in this regard http://www.ada-auth.org/standards/12rat/html/Rat12-1-3-2.html but it's a bit late. I'm glad to hear that Ada use is increasing somewhere, but I don't see it in any market I look at. The Rust designers are targetting C and C++ users, with a different vision than Walter and Andrei's as to what constitutes C++ done right, and some specific applications, like Servo. -- Brian
Re: Ada conference, Ada and Spark
On Friday, 21 February 2014 at 15:57:32 UTC, Thiez wrote: That is not true, Rust has several keywords that are more than 5 characters, such as 'continue'. The full list is here: http://static.rust-lang.org/doc/master/rust.html#keywords . It is true that they prefer short keywords over long ones. I knew there was no hard-coded limit, but this try to keep keywords short sounds really stupid to me. No offence to designers, but I really don't think we should save some spar characters in 2014... I do all my coding on a remote SSH, but still I have plenty of screen space to spare ;) My first glance: priv instead of private... bleah! At least it's clear enough mut... what is this? mutable, mutex, perhaps mute? impl could be several different things, too, but I guess it's implements And continue being a different keyword some time ago. In the end they changed it. Tons of discussions and stuff; was it worth saving 3 characters, after all? I hope their standard library is at least WAY more verbose... Otherwise I pity casual Rust programmers :D
Re: Ada conference, Ada and Spark
Am 21.02.2014 16:57, schrieb Thiez: On Friday, 21 February 2014 at 14:27:48 UTC, Paulo Pinto wrote: On Friday, 21 February 2014 at 13:08:37 UTC, Francesco Cattoglio wrote: On Friday, 21 February 2014 at 12:56:32 UTC, Paulo Pinto wrote: That is easy to answer, I doubt they could with their rule of not having more than 5 characters per keyword. :) Wait, what? REALLY? What kind of rule is that. ahahahha... are they stuck to the 70's? :D Yes really, http://forum.dlang.org/post/glnafbocwjodiwrqw...@forum.dlang.org I just cannot find the Reddit thread any longer. That is not true, Rust has several keywords that are more than 5 characters, such as 'continue'. The full list is here: http://static.rust-lang.org/doc/master/rust.html#keywords . It is true that they prefer short keywords over long ones. It used to be the case that 'loop' could mean 'continue' but people found it confusing so it was fixed. What I was arguing in that old thread was things like pub vs public, mut vs mutable and so on. I have a strong ML background as my university teachers were quite found of ML and we had a few courses using Caml Light. So I do like Rust and my issue back then was why to short those keywords and similar. Then again as I come from Pascal family of languages and always liked a bit verbosity, instead of the write only way of C. -- Paulo
Re: Ada conference, Ada and Spark
On 21 February 2014 20:00, Tobias Pankrath tob...@pankrath.net wrote: Depends on how often and where you write those keywords. mut seems to be quite common and even in D I would not like 'reference' more than 'ref', especially since it is used in parameter lists. I think Rust's pub, priv and fn are just silly. But I don't mind mut. However it might've been nicer if you didn't have to write let mut but just mut. What made Rust a no-go for me was when I tried to write a generic sort. I still can't figure out how to swap two elements in an array (vector). The implementation in their std lib for swap has an unsafe block... (And I don't want a GC or RC requirement for the array.)
Re: Ada conference, Ada and Spark
On Wednesday, 19 February 2014 at 23:55:16 UTC, bearophile wrote: Related to the Mars lander software thread. They have released the slides for the FOSDEM 2014 (1 February 2014) conference about Ada and related things (http://people.cs.kuleuven.be/~dirk.craeynest/ada-belgium/events/14/140201-fosdem.html ). ... I have been following Ada at FOSDEM for the last years, and its use seems to be increasing in Europe for safety critical systems, mainly thanks to C and C++ issues. Maybe this is an area where D could be pushed as well. -- Paulo
Re: Ada conference, Ada and Spark
On Wednesday, 19 February 2014 at 23:55:16 UTC, bearophile wrote: Integral ranges and strong types: type Age is range 0..125; type Floor is range -5 .. 15; Is it possible to implement this using the information that's already available through Value Range Propagation? I think I remember Andrei describing it in TDPL as numeric values carrying around their ranges at compile time, but I don't remember exactly. My_Age : Age; My_Floor : Floor; ... My_Age := 10; -- OK My_Floor := 10; -- OK My_Age := My_Floor; -- FORBIDDEN ! How close do you think std.typecons.Typedef is to supporting this functionality? Is it a sufficient replacement? Discriminated types: ype Major is (Letters, Sciences, Technology); type Grade is delta 0.1 range 0.0 .. 20.0; type Student_Record (Name_Length : Positive; With_Major : Major) is record Name: String(1 .. Name_Length); --Size depends on discriminant English : Grade; Maths : Grade; case With_Major is -- Variant part, according to discriminant when Letters = Latin : Grade; when Sciences = Physics : Grade; Chemistry : Grade; when Technology = Drawing : Grade; end case; end record; Ditto, except for with std.variant.Algebraic. It does need some work, but I think the important part is whether it's implementable in the library with a nice syntax. Then it only requires somebody to do the necessary work. Low level description of a record: type BitArray is array (Natural range ) of Boolean; type Monitor_Info is record On : Boolean; Count : Natural range 0..127; Status : BitArray (0..7); end record; for Monitor_Info use record On at 0 range 0 .. 0; Count at 0 range 1 .. 7; Status at 0 range 8 .. 15; end record; Isn't this the same as a struct? Static predicates (related to the enum preconditions I suggested for D): procedure Seasons is type Months is (Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec); subtype Summer is Months with Static_Predicate = Summer in Nov .. Dec | Jan .. Apr; A_Summer_Month : Summer; begin A_Summer_Month := Jul; end Seasons; The code gives: warning: static expression fails static predicate check on Summer What are the limitations on what Static_Predicate can verify? It seems like this could be quite powerful, but not as powerful as runtime checks, since not everything can be checked at compile time. A kind of set syntax: elsif First and then C in '+' | '0' .. ’9’ then I think this would be quite easy to do using mixins. I've also been thinking about list comprehensions a la Python, done with mixins. Loop variants and invariants: procedure Loop_Var_Loop_Invar is type Total is range 1 .. 100; subtype T is Total range 1 .. 10; I : T := 1; R : Total := 100; begin while I 10 loop pragma Loop_Invariant (R = 100 - 10 * I); pragma Loop_Variant (Increases = I, Decreases = R); R := R - I; I := I + 1; end loop; end Loop_Var_Loop_Invar; This is a neat feature. I thought it was unique to Wiley, but I guess the creator of Wiley must've got it from Ada. Does the loop break if the invariant fails, or does it stop the program? An example in Spark, to clarify access to global variables (for D I suggested a simpler optional @outer() attribute: https://d.puremagic.com/issues/show_bug.cgi?id=5007 ): ... I don't think this is quite as important, seeing as D has the pure keyword.
Re: Ada conference, Ada and Spark
Meta: What are the limitations on what Static_Predicate can verify? It seems like this could be quite powerful, but not as powerful as runtime checks, since not everything can be checked at compile time. In Ada there is Dynamic_Predicate for the other cases :-) Does the loop break if the invariant fails, or does it stop the program? Ada has an elaborate infrastructure to allow you to choose how to react to failures, how to handle them, what failures to ignore, etc. At least, it stops the program. I don't think this is quite as important, seeing as D has the pure keyword. Purity means you can't use mutable values from outer scopes. The point of those Spark annotations (and @outer()) is to do the opposite: to specify the flow of information in system programming when you are not using purity. Bye, bearophile
