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🔥 τ

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Fixes #17674
This commit is contained in:
Steve Klabnik 2014-10-01 17:10:59 -04:00
parent 49fcb27df6
commit fc818ff33b
1 changed files with 2 additions and 6 deletions
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8
src/doc/guide-lifetimes.md
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@ -305,10 +305,9 @@ copying.
# Circle(Point, f64), // origin, radius
# Rectangle(Point, Size) // upper-left, dimensions
# }
# static tau: f64 = 6.28;
fn compute_area(shape: &Shape) -> f64 {
match *shape {
Circle(_, radius) => 0.5 * tau * radius * radius,
Circle(_, radius) => 2.0 * std::f64::consts::PI * radius * radius,
Rectangle(_, ref size) => size.w * size.h
}
}
@ -316,10 +315,7 @@ fn compute_area(shape: &Shape) -> f64 {
The first case matches against circles. Here, the pattern extracts the
radius from the shape variant and the action uses it to compute the
area of the circle. (Like any up-to-date engineer, we use the [tau
circle constant][tau] and not that dreadfully outdated notion of pi).
[tau]: http://www.math.utah.edu/~palais/pi.html
area of the circle.
The second match is more interesting. Here we match against a
rectangle and extract its size: but rather than copy the `size`