[rust-dev] "let mut" <-> "var"
space.ship.traveller at gmail.com
Wed Jan 29 19:18:18 PST 2014
Do you think for client code it would be the same proportion as in
On 30 January 2014 16:13, Huon Wilson <dbau.pp at gmail.com> wrote:
> On 30/01/14 14:09, Samuel Williams wrote:
> I agree that it is syntactic salt and that the design is to discourage
> mutability. I actually appreciate that point as a programmer.
> w.r.t. this specific issue: I think what concerns me is that it is quite
> a high burden for new programmers (I teach COSC1xx courses to new students
> so I have some idea about the level of new programmers). For example, you
> need to know more detail about what is going on - new programmers would
> find that difficult as it is one more concept to overflow their heads.
> Adding "var" as a keyword identically maps to new programmer's
> wouldn't cause any problems right? But, could be optimised more
> (potentially) if using "let" for immutable parts.
> Anyway, I'm not convinced either way, I'm not sure I see the entire
> picture yet. But, if I was writing code, I'd certainly get sick of writing
> "let mut" over and over again - and looking at existing rust examples, that
> certainly seems like the norm..
> Inside the main rust repository:
> $ git grep 'let ' -- '*.rs' | grep -v mut | wc -l
> $ git grep 'let ' -- '*.rs' | grep mut | wc -l
> i.e. there are approximately 3 times more non-mutable variable bindings
> than there are mutable ones.
> On 30 January 2014 15:59, Samuel Williams <space.ship.traveller at gmail.com>wrote:
>> I guess the main gain would be less typing of what seems to be a
>> reasonably common sequence, and the formalisation of a particular semantic
>> pattern which makes it easier to recognise the code when you visually
>> scanning it.
>> On 30 January 2014 15:50, Kevin Ballard <kevin at sb.org> wrote:
>>> On Jan 29, 2014, at 6:43 PM, Brian Anderson <banderson at mozilla.com>
>>> > On 01/29/2014 06:35 PM, Patrick Walton wrote:
>>> >> On 1/29/14 6:34 PM, Samuel Williams wrote:
>>> >>> Perhaps this has been considered already, but when I'm reading rust
>>> >>> "let mut" just seems to stick out all over the place. Why not add a
>>> >>> "var" keyword that does the same thing? I think there are lots of
>>> >>> and bad reasons to do this or not do it, but I just wanted to propose
>>> >>> the idea and see what other people are thinking.
>>> >> `let` takes a pattern. `mut` is a modifier on variables in a pattern.
>>> It is reasonable to write `let (x, mut y) = ...`, `let (mut x, y) = ...`,
>>> `let (mut x, mut y) = ...`, and so forth.
>>> >> Having a special "var" syntax would defeat this orthogonality.
>>> > `var` could potentially just be special-case sugar for `let mut`.
>>> To what end? Users still need to know about `mut` for all the other
>>> uses of patterns. This would reserve a new keyword and appear to duplicate
>>> functionality for no gain.
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