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A "Design FAQ" document #891

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steveklabnik opened this issue Feb 20, 2015 · 23 comments
Closed

A "Design FAQ" document #891

steveklabnik opened this issue Feb 20, 2015 · 23 comments

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@steveklabnik
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Issue by bstrie
Tuesday Nov 27, 2012 at 20:34 GMT

For earlier discussion, see rust-lang/rust#4047

This issue was labelled with: A-docs, I-wishlist in the Rust repository

In the vein of the Project FAQ and the Language FAQ.

In addition to being really interesting, this would save a lot of time and divert a lot of potential questions in the long run. Some topics to discuss:

  • Why was typestate removed?
  • Why are some types nominal instead of structural?
  • Why do I have to declare impls in the same crate as a type or trait?
  • Why is trait inheritance the only means of inheritance?
  • Why doesn't Rust do tail-call optimization?
    (see e.g. rust-dev post.)

Explanations should be technical and include code examples wherever possible.

Some of the questions of this nature overlap with the latter half of the Language FAQ, but not all, e.g. "Can Rust code call C code?" and "What is the difference between a managed pointer and an owned pointer?" do not belong. The document should focus on large-scale design decisions and tradeoffs; think "Why split stacks?" rather than "How do split stacks work?".

If you think of good questions, add them in the comments here. There are probably a lot of ripe areas for explanation, especially with regard to mutability and regions.
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Comment by brson
Tuesday Nov 27, 2012 at 21:24 GMT

The manual has a related (and empty) section: http://dl.rust-lang.org/doc/0.4/rust.html#appendix-rationales-and-design-tradeoffs

@steveklabnik steveklabnik mentioned this issue Feb 20, 2015
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Comment by bstrie
Thursday Nov 29, 2012 at 18:53 GMT

Why are &str, @str, ~str, &[], @[], and ~[] treated differently from &T, @T, and ~T?

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Comment by bstrie
Wednesday Dec 05, 2012 at 15:56 GMT

Why are early returns disallowed within closures?

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Comment by bstrie
Friday Dec 07, 2012 at 18:19 GMT

Why are separate do and for constructs required?

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Comment by bstrie
Tuesday Dec 11, 2012 at 12:45 GMT

Why do traits in Rust depart from the design in the original traits paper?

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Comment by bstrie
Tuesday Jan 01, 2013 at 18:07 GMT

Why must imports be qualified relative to the crate?

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Comment by graydon
Wednesday Jan 02, 2013 at 03:38 GMT

These are great, please keep them coming

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Comment by catamorphism
Wednesday Jan 02, 2013 at 21:59 GMT

"What does const mean (and why)?" should be in there too, though I know we're thinking about renaming it (at least).

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Comment by bstrie
Thursday Jan 17, 2013 at 13:47 GMT

Why feature conditions rather than exceptions?

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Comment by jruderman
Tuesday Jan 29, 2013 at 22:50 GMT

Why so many pointer types? Why not rely on escape analysis instead?

Answered at:

http://www.reddit.com/r/programming/comments/17hqg4/a_little_bit_rusty_practical_approach_on_rust/c85r1nc

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Comment by bstrie
Thursday Jan 31, 2013 at 13:26 GMT

Why is the .times() method no longer defined on signed integers? (discussion on the specifics of integer literal inference)

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Comment by bstrie
Thursday Feb 21, 2013 at 15:06 GMT

Why do borrow checks on @mut pointers happen at runtime?

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Comment by fread2281
Sunday Mar 24, 2013 at 21:40 GMT

Why are there no exceptions?

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Comment by bstrie
Tuesday Apr 02, 2013 at 19:12 GMT

Why is name resolution such an intractably hard problem?

<@pcwalton> I know of no other static language with declarative imports
            that allows (a) reexports; (b) glob import; (c) mutual
            recursion everywhere; (d) nested modules; (e) two namespaces
<@pcwalton> java doesn't have reexports, Go doesn't have nested modules
            or reexports, C# doesn't have reexports I don't think, C++
            doesn't have reexports or mutual recursion everywhere, maybe
            D...
<@pcwalton> ML and Haskell don't have mutual recursion everywhere and
            don't have reexports
<@pcwalton> mutually recursive modules too
<@pcwalton> most languages do not have mutually recursive modules
< bstrie> pcwalton: so what you're saying is that rust has once again
          failed to be unoriginal :)
<@pcwalton> well, as you said, Python
<@pcwalton> but Rust is trying to achieve Python's module system's
            expressive power in a static system
  jld tries to remember how the various Scheme module systems work
<@pcwalton> turns out that's pretty hard :)
<@pcwalton> jld: no mutual recursion
<@pcwalton> btw, ES6 hit the exact same problems we did
<@pcwalton> and had to pare down their module system as a result
<@pcwalton> anyway none of this is an excuse, we should make it easier to
            use
<@pcwalton> but I'm just saying it's not that easy...

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Comment by brson
Tuesday Apr 30, 2013 at 22:04 GMT

Here's a summary about dynamically sized types https://mail.mozilla.org/pipermail/rust-dev/2013-April/003933.html

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Comment by brson
Tuesday Apr 30, 2013 at 22:39 GMT

Summary of 'why no exceptions' https://mail.mozilla.org/pipermail/rust-dev/2013-April/003815.html

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Comment by catamorphism
Tuesday Apr 30, 2013 at 22:43 GMT

Summary of 'why no purity-in-the-type-system, i.e., why no effect system': https://mail.mozilla.org/pipermail/rust-dev/2013-April/003926.html

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Comment by iampiyush
Thursday Jun 13, 2013 at 13:57 GMT

document how to make non-utf8 byte vectors with bytes!(…)

e.g.
use of bytes!("hell", 0xc0, 0xca, "o!") instead of bytes!("hell\xc0\xca\o1!")

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Comment by brson
Tuesday Jul 30, 2013 at 16:39 GMT

-> in function syntax: https://mail.mozilla.org/pipermail/rust-dev/2013-July/005042.html

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Comment by kud1ing
Monday Aug 05, 2013 at 10:06 GMT

Why have we mostly moved from internal iterators to external iterators?
https://mail.mozilla.org/pipermail/rust-dev/2013-June/004364.html

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Comment by kud1ing
Thursday Aug 08, 2013 at 07:23 GMT

Why was the runtime ported from C++ to Rust?

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Comment by brson
Wednesday Dec 04, 2013 at 20:11 GMT

Why is rustc slow? https://mail.mozilla.org/pipermail/rust-dev/2013-November/006975.html

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Import rate limiting made this fail :( re-opening the original: #615

@steveklabnik steveklabnik mentioned this issue Feb 23, 2015
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