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Add implementation on Option is confusing #8127

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Kimundi opened this issue Jul 30, 2013 · 3 comments
Closed

Add implementation on Option is confusing #8127

Kimundi opened this issue Jul 30, 2013 · 3 comments

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@Kimundi
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Kimundi commented Jul 30, 2013

Right now add on two Options effectively treats a None as a Some(Zero::zero()), which is:

  • Unnecessary because Some(Zero::zero()) is already a valid value, why duplicate it's meaning with None?
  • Contrary to the way the Maybe Monad in Haskell works: If both values are a Some, add them, else return None.
@bstrie
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bstrie commented Jul 30, 2013

I think this might be a dup of #6002, but what does this have to do with Zero::zero()?

@Kimundi
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Kimundi commented Jul 30, 2013

@bstrie: Maybe I expressed it strange :)

What I mean is: If the implementation is such that Some(n) + None = Some(n), then None becomes then additive neutral element for, eg Option<uint>. But that is unnecessary because Option<uint> already has a additive neutral element: Some(0). A None is a separate value from any other Some(n), If you treat it the same as Some(0) you might as well not have an Option-value at all.

My talk about Zero::zero() was just an attempt to talk about the generic additive neutral element. :)

@Kimundi
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Kimundi commented Jul 30, 2013

Anyway, this is indeed a duplicate of that issue, closing this one.

@Kimundi Kimundi closed this as completed Jul 30, 2013
flip1995 pushed a commit to flip1995/rust that referenced this issue Dec 30, 2021
@bors
Auto merge of rust-lang#8127 - dswij:8090, r=xFrednet
56ccd30 
Fix `enum_variants` FP on prefixes that are not camel-case

closes rust-lang#8090

Fix FP on `enum_variants` when prefixes are only a substring of a camel-case word. Also adds some util helpers on `str_utils` to help parsing camel-case strings.

This changes how the lint behaves:

1. previously if the Prefix is only a length of 1, it's going to get ignored, i.e. these were previously ignored and now is warned
```rust
enum Foo {
    cFoo,
    cBar,
    cBaz,
}

enum Something {
    CCall,
    CCreate,
    CCryogenize,
}
```

2. non-ascii characters that doesn't have casing will not be split,
```rust
enum NonCaps {
    PrefixXXX,
    PrefixTea,
    PrefixCake,
}
```
will be considered as `PrefixXXX`, `Prefix`, `Prefix`, so this won't lint as opposed to fired previously.

changelog: [`enum_variant_names`] Fix FP when first prefix are only a substring of a camel-case word.

---

 (Edited by `@xFrednet` removed some non ascii characters)
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@bstrie @Kimundi