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Add missing example for Display::fmt #40299

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merged 1 commit into from
Mar 12, 2017

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GuillaumeGomez
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/// fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
/// match *self {
/// Foo::Bar => write!(f, "Foo::Bar"),
/// Foo::Stack => write!(f, "Foo::Stack"),
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This is slightly confusing because it looks like a Debug representation. How do you feel about getting rid of the Foo:: in the outputted string?

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@GuillaumeGomez GuillaumeGomez Mar 7, 2017

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I always add the enum's name first in case you have multiple wrappings:

enum Foo {
    A,
}

enum X {
    A(Foo),
}

enum Y {
    A(X),
}

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@frewsxcv frewsxcv Mar 8, 2017

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I think you're mixing up Debug and Display. Display is for user-facing output. Users shouldn't care about enum namespacing. We don't want to encourage Rust developers to implement Display if their types aren't mean to be displayed to end-users.
How about this as the example:

struct Position {
    longitude: f32,
    latitude: f32,
}

impl fmt::Display for Position {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        write!(f, "({}, {})", self.longitude, self.latitude)
    }
}

This seems a little more realistic than Foo and Bar and Stack ;)

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Why so cruel? :O

@GuillaumeGomez
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Updated.

@frewsxcv
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@bors r+ rollup

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bors commented Mar 11, 2017

📌 Commit a5a3981 has been approved by frewsxcv

arielb1 pushed a commit to arielb1/rust that referenced this pull request Mar 11, 2017
… r=frewsxcv

Add missing example for Display::fmt

r? @frewsxcv
bors added a commit that referenced this pull request Mar 11, 2017
Rollup of 13 pull requests

- Successful merges: #40146, #40299, #40315, #40319, #40344, #40345, #40367, #40372, #40373, #40385, #40400, #40404, #40431
- Failed merges:
arielb1 pushed a commit to arielb1/rust that referenced this pull request Mar 11, 2017
… r=frewsxcv

Add missing example for Display::fmt

r? @frewsxcv
bors added a commit that referenced this pull request Mar 12, 2017
Rollup of 12 pull requests

- Successful merges: #40146, #40299, #40315, #40319, #40344, #40345, #40372, #40373, #40400, #40404, #40419, #40431
- Failed merges:
@bors bors merged commit a5a3981 into rust-lang:master Mar 12, 2017
@GuillaumeGomez GuillaumeGomez deleted the fmt-display-example branch March 13, 2017 10:24
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3 participants