X-Git-Url: https://git.ralfj.de/rust-101.git/blobdiff_plain/942f0abd4b0931acad2d3def58cb7273ace15e2a..1f6a5ed7a44ed00827fd3312503f20b8f52f94db:/src/part10.rs?ds=inline diff --git a/src/part10.rs b/src/part10.rs index c8a0129..53110dc 100644 --- a/src/part10.rs +++ b/src/part10.rs @@ -1,8 +1,7 @@ // Rust-101, Part 10: Closures // =========================== -use std::io::prelude::*; -use std::{fmt,io}; +use std::fmt; use part05::BigInt; //@ Assume we want to write a function that does *something* on, say, every digit of a `BigInt`. @@ -24,7 +23,7 @@ impl BigInt { //@ Remember that the `mut` above is just an annotation to Rust, telling it that we're okay with `a` being mutated. //@ Calling `do_action` on `a` takes a mutable borrow, so mutation could indeed happen. for digit in self { - a.do_action(digit); + a.do_action(digit); /*@*/ } } } @@ -40,7 +39,7 @@ impl Action for PrintWithString { // Here we perform performs the actual printing of the prefix and the digit. We're not making use of our ability to // change `self` here, but we could replace the prefix if we wanted. fn do_action(&mut self, digit: u64) { - println!("{}{}", self.prefix, digit); + println!("{}{}", self.prefix, digit); /*@*/ } } @@ -73,7 +72,7 @@ impl BigInt { fn act(&self, mut a: A) { for digit in self { // We can call closures as if they were functions - but really, what's happening here is translated to essentially what we wrote above, in `act_v1`. - a(digit); + a(digit); /*@*/ } } } @@ -115,7 +114,7 @@ fn inc_print_even(v: &Vec, offset: i32, threshold: i32) { //@ //@ Since all these closures compile down to the pattern described above, there is actually no heap allocation going on here. This makes //@ closures very efficient, and it makes optimization fairly trivial: The resulting code will look like you hand-rolled the loop in C. - for i in v.iter().map(|n| n + offset).filter(|n| *n > threshold) { + for i in v.iter().map(|n| *n + offset).filter(|n| *n > threshold) { println!("{}", i); } } @@ -134,7 +133,7 @@ fn filter_vec_by_divisor(v: &Vec, divisor: i32) -> Vec { //@ Here, the return type of `collect` is inferred based on the return type of our function. In general, it can return anything implementing //@ [`FromIterator`](http://doc.rust-lang.org/stable/std/iter/trait.FromIterator.html). Notice that `iter` gives us an iterator over //@ borrowed `i32`, but we want to own them for the result, so we insert a `map` to dereference. - v.iter().map(|n| *n).filter(|n| *n % divisor == 0).collect() + v.iter().map(|n| *n).filter(|n| *n % divisor == 0).collect() /*@*/ } // **Exercise 10.1**: Look up the [documentation of `Iterator`](http://doc.rust-lang.org/stable/std/iter/trait.Iterator.html) to learn about more functions @@ -142,4 +141,4 @@ fn filter_vec_by_divisor(v: &Vec, divisor: i32) -> Vec { // product of those numbers that sit at odd positions? A function that checks whether a vector contains a certain number? Whether all numbers are // smaller than some threshold? Be creative! -//@ [index](main.html) | [previous](part08.html) | [next](main.html) +//@ [index](main.html) | [previous](part09.html) | [next](part11.html)