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Rust from Python & Ruby

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Armin Ronacher @mitsuhiko Python Dude (with Ruby experience)

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What is Rust?

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Programming Language printf("Hello " "World!\n");

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UNDER CONSTRUCTION

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def main(): for name in ["Peter", "Paul", "Mary"]: print "Hello %s!" % name

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def main ["Peter", "Paul", "Mary"].each do |name| puts "Hello %s!" % name end end

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fn main() { for ["Peter", "Paul", "Mary"].each |name| { io::println(fmt!("Hello %s!", *name)); } }

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fn main() { let s = [1, 2, 3, 4].map(|x| (*x * *x).to_str()); for s.each |item| { io::println(*item); } }

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fn main() { let s = [1, 2, 3, 4].map(|&x| (x * x).to_str()); for s.each |&item| { io::println(item); } } Soon TM

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fn main() { let x = 42; let y = &x; let &z = y; io::println(fmt!("%d", z + z)); }

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$ cat hello.rs fn main() { io::println("Hello World!"); } $ rustc -g hello.rs $ ./hello Hello World! Compile that

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In a Nutshell

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✤ immutable by default ✤ static, algebraic, locally inferred types ✤ no dangling pointers, no overflows ✤ lightweight green tasks ✤ ahead-of-time compiled ✤ C compatible

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-FUTMPPLDMPTFS

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fn main() { for ["Peter", "Paul", "Mary"].each |name| { io::println(fmt!("Hello %s!", *name)); } }

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fn main() { ["Peter", "Paul", "Mary"].each(|name| { io::println(fmt!("Hello %s!", *name)); true }); }

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Expressions

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fn main() { let a = [1, 2, 3].map(|x| { *x; }); let b = [1, 2, 3].map(|x| { *x }); io::println(fmt!("a=%? b=%?", a, b)); } /* a=~[ (), (), () ] b=~[ 1, 2, 3 ] */

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Traits and Implementations

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trait LengthPrintable { fn print_length(); }

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impl &[T]: LengthPrintable { fn print_length() { io::println(fmt!("length = %u", self.len())); } }

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fn main() { ["Peter", "Paul", "Mary"].print_length(); }

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Memory Ownership

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fn main() { let name = ~"Peter"; let new_name = name; io::println(fmt!("Hello %s!", name)); } Does not compile: string (currently) does not copy

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fn main() { let name = ~"Peter"; let new_name = move name; io::println(fmt!("Hello %s!", name)); } Does not compile: using moved-out value

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fn main() { let name = ~"Peter"; let new_name = move name; io::println(fmt!("Hello %s!", new_name)); } That compiles!

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Not Null (algebraic data types)

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def first_larger(seq, x): for item in seq: if item > x: return x Where is the NULL?

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fn first_larger(seq: &[int], x: int) -> Option { for seq.each |item| { if *item > x { return Some(*item); } } None }

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fn main() { let rv = first_larger([1, 2, 3, 4, 5], 3); io::println(match rv { Some(num) => fmt!("Found %d", num), None => ~"No number found" }); }

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Pattern Matching!

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Enums (better than C's)

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enum Shape { Point, Circle(float), Rect(float, float) }

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impl Shape : ToStr { pure fn to_str() -> ~str { match self { Point => ~"point", Circle(r) => fmt!("circle of %f", r), Rect(w, h) => fmt!("rect of %f by %f", w, h) } } }

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fn main() { let p = Point; let c = Circle(4.0f); io::println(fmt!("p=%s, c=%s", p.to_str(), c.to_str())); }

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“Classes”

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struct Point { mut x: float, mut y: float, } impl Point { static fn new(x: float, y: float) -> Point { Point { x: x, y: y } } }

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impl Point : ToStr { pure fn to_str() -> ~str { fmt!("(%f, %f)", self.x, self.y) } }

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fn main() { let p = Point::new(0.0f, 0.0f); io::println(p.to_str()); }

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Hold on a second! */)&3*5"/$& ?

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trait inheritance no data inheritance !

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Tasks

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fn main() { for ["Peter", "Paul", "Mary"].each |name| { let name = *name; do task::spawn { let v = rand::Rng().shuffle([1, 2, 3]); for v.each |num| { io::print(fmt!("%s says: '%d'\n", name, *num)); } } } }

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FFI

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#[link_args="-lcrypto"] extern { fn SHA1(s: *u8, l: libc::c_uint, d: *u8) -> *u8; } fn sha1(data: &str) -> ~str { unsafe { let bytes = str::to_bytes(data); let mut buf = [0u8, ..20]; SHA1(vec::raw::to_ptr(bytes), bytes.len() as libc::c_uint, vec::raw::to_ptr(buf)); as_hex(buf) } }

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fn as_hex(data: &[u8]) -> ~str { let mut rv = ~""; for data.each |b| { rv += fmt!("%02x", *b as uint); } move rv } fn main() { io::println(sha1("Hello World!")); }

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bindgen for the lazy:

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Dear god … Why?

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Why a new language?

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Hello Concurrency

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Why is concurrency messy?

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Q: Why are global variables bad? A: there is only one of them!

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Concurrency in web apps: What do you actually share?

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Memory Tracking Enables Cheap Message Passing

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Spaghetti Stacks

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The Problems with Rust

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strings not implicitly copyable

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ownership tracking not perfect yet

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generics are harder to implement

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Option is a bit of a pain

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directly using C APIs is icky

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task scheduler oblivious of libuv

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incomplete / work in progress

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Q&A Thanks, now there is time for … @mitsuhiko http://lucumr.pocoo.org/ http:// reteam.net/