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Deprecate stdlib modules dedicated to numeric constants and move those constants to associated consts #2700

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Merged
merged 13 commits into from
Jan 23, 2020
Merged

Deprecate stdlib modules dedicated to numeric constants and move those constants to associated consts #2700

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8ceca52
Initial draft
May 13, 2019
10b9307
Formatting
May 13, 2019
e3de748
Expand on alternatives and rationale WRT floats
May 14, 2019
972d24a
Exclude fXX::consts from this RFC
faern Nov 20, 2019
a3fa24c
Add one benefit of doing this
faern Nov 20, 2019
b9a1439
Break lines on 100 chars and update rationale/alternatives
faern Nov 20, 2019
2f3e4c9
Update and polish
Dec 4, 2019
a72cf50
Further rationale and alternatives
Dec 4, 2019
8881377
Nits
Dec 4, 2019
6993187
Additional motivation
Dec 4, 2019
5352bf9
Add MIN_10_EXP, which was mistakenly omitted
Jan 17, 2020
4ec5877
Shuffle guide-level steps and deprecation question
Jan 17, 2020
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Fill links for RFC 2700
LukasKalbertodt Jan 23, 2020
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Exclude fXX::consts from this RFC
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@faern
faern committed Nov 20, 2019
commit 972d24a9cb7cad32e13c11d8ed35afecc759b06a
69 changes: 3 additions & 66 deletions text/0000-associated-constants-on-ints.md
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Expand Up @@ -27,7 +27,7 @@ Finally, so obvious was this solution that [the original RFC for associated item

> For example, today's Rust includes a variety of numeric traits, including Float, which must currently expose constants as static functions [...] Associated constants would allow the consts to live directly on the traits

Despite the obvious intent, 1.0 came and went and there were plenty of other things to occupy everyone's attention. Now, two days shy of Rust's fourth anniversary, let's re-examine the situation. We propose to deprecate all of the aforementioned functions and constants in favor of associated constants defined on the appropriate types, and to additionally deprecate the `i8`, `i16`, `i32`, `i64`, `i128`, `isize`, `u8`, `u16`, `u32`, `u64`, `u128`, `usize`, `f32`, and `f64` modules in `std`. Advantages of this:
Despite the obvious intent, 1.0 came and went and there were plenty of other things to occupy everyone's attention. Now, two days shy of Rust's fourth anniversary, let's re-examine the situation. We propose to deprecate all of the aforementioned functions and constants in favor of associated constants defined on the appropriate types, and to additionally deprecate all constants living directly in the `i8`, `i16`, `i32`, `i64`, `i128`, `isize`, `u8`, `u16`, `u32`, `u64`, `u128`, `usize`, `f32` and `f64` modules in `std`. But leaving `std::f64::consts` and `std::f32::consts` as they are. Advantages of this:

1. Consistency with the rest of the language. As demonstrated by the above quotes, associated consts have been the natural way to express these concepts in Rust since before associated consts were even implemented; this approach satisfies the principle of least surprise.

Expand Down Expand Up @@ -164,38 +164,6 @@ Deprecate the following items in the standard library:

[std::f32::RADIX](https://doc.rust-lang.org/std/f32/constant.RADIX.html)

[std::f32::consts::E](https://doc.rust-lang.org/std/f32/consts/constant.E.html)

[std::f32::consts::FRAC_1_PI](https://doc.rust-lang.org/std/f32/consts/constant.E.html)

[std::f32::consts::FRAC_2_PI](https://doc.rust-lang.org/std/f32/consts/constant.FRAC_2_PI.html)

[std::f32::consts::FRAC_2_SQRT_PI](https://doc.rust-lang.org/std/f32/consts/constant.FRAC_2_SQRT_PI.html)

[std::f32::consts::FRAC_1_SQRT_2](https://doc.rust-lang.org/std/f32/consts/constant.FRAC_1_SQRT_2.html)

[std::f32::consts::FRAC_PI_2](https://doc.rust-lang.org/std/f32/consts/constant.FRAC_PI_2.html)

[std::f32::consts::FRAC_PI_3](https://doc.rust-lang.org/std/f32/consts/constant.FRAC_PI_3.html)

[std::f32::consts::FRAC_PI_4](https://doc.rust-lang.org/std/f32/consts/constant.FRAC_PI_4.html)

[std::f32::consts::FRAC_PI_6](https://doc.rust-lang.org/std/f32/consts/constant.FRAC_PI_6.html)

[std::f32::consts::FRAC_PI_8](https://doc.rust-lang.org/std/f32/consts/constant.FRAC_PI_8.html)

[std::f32::consts::LN_2](https://doc.rust-lang.org/std/f32/consts/constant.LN_2.html)

[std::f32::consts::LN_10](https://doc.rust-lang.org/std/f32/consts/constant.LN_10.html)

[std::f32::consts::LOG2_E](https://doc.rust-lang.org/std/f32/consts/constant.LOG2_E.html)

[std::f32::consts::LOG10_E](https://doc.rust-lang.org/std/f32/consts/constant.LOG10_E.html)

[std::f32::consts::PI](https://doc.rust-lang.org/std/f32/consts/constant.PI.html)

[std::f32::consts::SQRT_2](https://doc.rust-lang.org/std/f32/consts/constant.SQRT_2.html)

[std::f64::DIGITS](https://doc.rust-lang.org/std/f64/constant.DIGITS.html)

[std::f64::EPSILON](https://doc.rust-lang.org/std/f64/constant.EPSILON.html)
Expand Down Expand Up @@ -224,39 +192,8 @@ Deprecate the following items in the standard library:

[std::f64::RADIX](https://doc.rust-lang.org/std/f64/constant.RADIX.html)

[std::f64::consts::E](https://doc.rust-lang.org/std/f64/consts/constant.E.html)

[std::f64::consts::FRAC_1_PI](https://doc.rust-lang.org/std/f64/consts/constant.E.html)

[std::f64::consts::FRAC_2_PI](https://doc.rust-lang.org/std/f64/consts/constant.FRAC_2_PI.html)

[std::f64::consts::FRAC_2_SQRT_PI](https://doc.rust-lang.org/std/f64/consts/constant.FRAC_2_SQRT_PI.html)

[std::f64::consts::FRAC_1_SQRT_2](https://doc.rust-lang.org/std/f64/consts/constant.FRAC_1_SQRT_2.html)

[std::f64::consts::FRAC_PI_2](https://doc.rust-lang.org/std/f64/consts/constant.FRAC_PI_2.html)

[std::f64::consts::FRAC_PI_3](https://doc.rust-lang.org/std/f64/consts/constant.FRAC_PI_3.html)

[std::f64::consts::FRAC_PI_4](https://doc.rust-lang.org/std/f64/consts/constant.FRAC_PI_4.html)

[std::f64::consts::FRAC_PI_6](https://doc.rust-lang.org/std/f64/consts/constant.FRAC_PI_6.html)

[std::f64::consts::FRAC_PI_8](https://doc.rust-lang.org/std/f64/consts/constant.FRAC_PI_8.html)

[std::f64::consts::LN_2](https://doc.rust-lang.org/std/f64/consts/constant.LN_2.html)

[std::f64::consts::LN_10](https://doc.rust-lang.org/std/f64/consts/constant.LN_10.html)

[std::f64::consts::LOG2_E](https://doc.rust-lang.org/std/f64/consts/constant.LOG2_E.html)

[std::f64::consts::LOG10_E](https://doc.rust-lang.org/std/f64/consts/constant.LOG10_E.html)

[std::f64::consts::PI](https://doc.rust-lang.org/std/f64/consts/constant.PI.html)

[std::f64::consts::SQRT_2](https://doc.rust-lang.org/std/f64/consts/constant.SQRT_2.html)

Replace each item with an associated const value on the appropriate type. Deprecate the fourteen numeric-type modules and remove them from the documentation.
Replace each item with an associated const value on the appropriate type. Deprecate the twelve
integer type modules and remove them from the documentation.

# Drawbacks
[drawbacks]: #drawbacks
Expand Down