[rust-dev] About const

[rust-dev] About const

[Pim Schellart]

Dear Rust Developers,

here is another ignorant question so feel free to ignore.
When reading the guide I came across "std::f64::consts::PI” for pi. Now I was wondering why there are separate constants defined for 32 and 64 bit floats and how this will work with generics. Do you always have to define two functions to work on f32 and f64 or is std::f64::consts::PI cast down to f32 in an equation with 32 bit variables? Is there also a general `typeless’ PI (or other fundamental constants), as in Go for example?

Kind Regards,

Pim

Re: [rust-dev] About const

[Manish Goregaokar]

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We have two types of floats, there is a Pi of both precision levels. I
don't think it's anything more than that. You should be able to cast
between the two, but that's it I guess. Rust tries to give explicit control
over such things.

There is a Float trait (might have been renamed) if you want to use
generics.

-Manish Goregaokar

On Sun, Jan 4, 2015 at 3:07 PM, Pim Schellart <p.schellart@gmail.com> wrote:

> Dear Rust Developers,
>
> here is another ignorant question so feel free to ignore.
> When reading the guide I came across "std::f64::consts::PI” for pi. Now I
> was wondering why there are separate constants defined for 32 and 64 bit
> floats and how this will work with generics. Do you always have to define
> two functions to work on f32 and f64 or is std::f64::consts::PI cast down
> to f32 in an equation with 32 bit variables? Is there also a general
> `typeless’ PI (or other fundamental constants), as in Go for example?
>
> Kind Regards,
>
> Pim
> _______________________________________________
> Rust-dev mailing list
> Rust-dev@mozilla.org
> https://mail.mozilla.org/listinfo/rust-dev
>

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Re: [rust-dev] About const

[Philippe Daouadi]

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If you want a generic pi, you should use the one in the Float trait

If you have
let x : f64 = ...;
x * Float::pi() will resolve to f64 pi

Philippe

On 01/04/2015 05:21 PM, Manish Goregaokar wrote:
> We have two types of floats, there is a Pi of both precision levels. I 
> don't think it's anything more than that. You should be able to cast 
> between the two, but that's it I guess. Rust tries to give explicit 
> control over such things.
>
> There is a Float trait (might have been renamed) if you want to use 
> generics.
>
> -Manish Goregaokar
>
> On Sun, Jan 4, 2015 at 3:07 PM, Pim Schellart <p.schellart@gmail.com 
> <mailto:p.schellart@gmail.com>> wrote:
>
>     Dear Rust Developers,
>
>     here is another ignorant question so feel free to ignore.
>     When reading the guide I came across "std::f64::consts::PI” for
>     pi. Now I was wondering why there are separate constants defined
>     for 32 and 64 bit floats and how this will work with generics. Do
>     you always have to define two functions to work on f32 and f64 or
>     is std::f64::consts::PI cast down to f32 in an equation with 32
>     bit variables? Is there also a general `typeless’ PI (or other
>     fundamental constants), as in Go for example?
>
>     Kind Regards,
>
>     Pim
>     _______________________________________________
>     Rust-dev mailing list
>     Rust-dev@mozilla.org <mailto:Rust-dev@mozilla.org>
>     https://mail.mozilla.org/listinfo/rust-dev
>
>
>
>
> _______________________________________________
> Rust-dev mailing list
> Rust-dev@mozilla.org
> https://mail.mozilla.org/listinfo/rust-dev


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Re: [rust-dev] About const

[Pim Schellart]

Ok, thanks!
> On 04 Jan 2015, at 17:57, Philippe Daouadi <blastrock0@free.fr> wrote:
> 
> If you want a generic pi, you should use the one in the Float trait
> 
> If you have
> let x : f64 = ...;
> x * Float::pi() will resolve to f64 pi
> 
> Philippe
> 
> On 01/04/2015 05:21 PM, Manish Goregaokar wrote:
>> We have two types of floats, there is a Pi of both precision levels. I don't think it's anything more than that. You should be able to cast between the two, but that's it I guess. Rust tries to give explicit control over such things.
>> 
>> There is a Float trait (might have been renamed) if you want to use generics.
>> 
>> -Manish Goregaokar
>> 
>> On Sun, Jan 4, 2015 at 3:07 PM, Pim Schellart <p.schellart@gmail.com> wrote:
>> Dear Rust Developers,
>> 
>> here is another ignorant question so feel free to ignore.
>> When reading the guide I came across "std::f64::consts::PI” for pi. Now I was wondering why there are separate constants defined for 32 and 64 bit floats and how this will work with generics. Do you always have to define two functions to work on f32 and f64 or is std::f64::consts::PI cast down to f32 in an equation with 32 bit variables? Is there also a general `typeless’ PI (or other fundamental constants), as in Go for example?
>> 
>> Kind Regards,
>> 
>> Pim
>> _______________________________________________
>> Rust-dev mailing list
>> Rust-dev@mozilla.org
>> https://mail.mozilla.org/listinfo/rust-dev
>> 
>> 
>> 
>> _______________________________________________
>> Rust-dev mailing list
>> 
>> Rust-dev@mozilla.org
>> https://mail.mozilla.org/listinfo/rust-dev
>