Section 1
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Create a simple hash map of two team scores (Blue:10 and Yellow:50).
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Section 1
(50 cards)
Create a simple hash map of two team scores (Blue:10 and Yellow:50).
use std::collections::HashMap; let mut scores = HashMap::new(); scores.insert(String::from("Blue"), 10); scores.insert(String::from("Yellow"), 50);
Increment vector elems with for.
let mut v = vec![1, 2, 3]; for i in &mut v { *i += 1; }
How Do I Cross-compile In Rust?
It is possible but need a bit of work to set up.
How to define array in Rust?
let x = [1, 2, 3];
What is crate?
Compilation unit.
Simple way to grow a String!
let mut s = String::from("Hello"); s.push_str(", world!");
How to get() element of a vector?
let v = vec![1, 2, 3]; match v.get(2) { Some(e) => println!("e: {}", e), None => println!("none"), }
What happens if we use slice of string (String or string literal) in a wrong way?
Panic in run time!
Write declaration of "ToString" train ("std::string::ToString").
pub trait ToString { fn to_string(&self) -> String; }
What part of Rust implements &str type?
Built-in type.
How to borrow the whole array as a slice?
let x = [1, 2, 3]; analyze_slice(&x);
Print command line arguments.
use std::env; for arg in env::args() { p!("{}", arg); }
How to borrow the third element of a vector?
let v = vec![1, 2, 3]; let third = &v[2]; print_third(third);
What part of Rust implements String type?
Standard library.
How to get grapheme clusters using Rust standard library?
No way. Use external crates.
Does Rust Have Move Constructors?
No, The values of all types are moved via memcpy.
How to print a number in binary format?
println!("{} of {:b} people know binary, the other half doesn't", 1, 2);
What is "{:?}" in println macro?
"fmt::Debug" uses the {:?} marker. Format text for debugging purposes.
Crate containts an implicit and un-named top-level [xxx].
module
Print UTF-8 string byte-by-byte.
for b in "abcБОРЩЬ".bytes() { println!("{}", b); }
Does Rust Guarantee A Specific Data Layout?
Not by default, Most of the general case, the enum and struct layouts are undefined.
How to store elements of different type in vector?
Vector of enums. enum SpreadCell { Int(i32), Text(String), } let v = vec![ SpreadCell::Int(3), SpreadCell::Text(String::from("blue")), };
What is the array signature?
[T; size]
How to pad right-aligned number with extra zeros?
println!("{num:>0width$}", num=1, width=6);
For what kind of types the values are COPIED to hash map?
For types that implement Copy trait (e.g., i32).
What Are The Disadvantages?
1) Rust compilation seems slow 2) Rust has a moderately-complex type system 3) The Rust compiler does not compile with optimizations unless asked to, as optimizations slow down compilation and are usually undesirable during development.
Print vector elems with for.
let v = vec![1, 2, 3]; for i in &v { println!("{}", i); }
How to print simple array in Rust?
let x = [1, 2, 3]; println!("Array is {:?}", x);
What data types are stored on stack?
Built-in array and tuples.
Simple way to create an empty vector of i32?
let v: Vec<i32> = Vec::new();
When vector is freed?
Like any other struct, a vector is freed when it goes out of scope.
Signature of std::string::String::push_str(...)?
pub fn push_str(&mut self, string: &str)
How to init all array elements to the same value?
let x = [0; 256];
Is Rust Object Oriented?
It is multi paradigm and most of the things can do in Rust but not everything. So, Rust is not object-oriented.
Create simple vector with 1, 2 and 3 using vector macro!
let v = vec![1, 2, 3];
What Is The Relationship Between A Module And A Crate?
Module - UNIT of code organization inside a crate. Crate - compilation UNIT.
For what kind of types the values are MOVED to hash map (and hash map becomes a new owner of those values)?
owned types that do NOT implement Copy trait (like std::String)
What's the difference between string.chars() and string.bytes()?
chars() - individual Unicode scalar values bytes() - raw bytes
Name simple methods to iterate over strings.
for c in "xxx".chars() { ... } for b in "yyy".bytes() { ... }
What is `std::string::ToString`?
Trait for converting a value to a `String`.
Create empty vector and add one i32 number.
let mut v = Vec::new(); v.push(5);
The idiomatic way of printing slice/array in hexadecimal?
let ciphertext: [u8; 256] = [0; 256]; println!("ciphertext is: {:?}", ciphertext);
How to print array size in bytes?
use std::mem; let x = [1, 2, 3]; println!("{} bytes", mem::size_of_val(&xs));
How to print with named arguments?
println!("{first} {sec}", first="xxx", sec="yyy");
How to print array size?
let x = [1, 2, 3]; println!("len: {}", x.len());
How to convert any type (that implements Display trait) to string?
let data = "initial contents"; let s = data.to_string();
What data types are stored on heap?
std::collections (vector, string, hash map and other).
How to print right-aligned text?
println!("{num:>width$}", num=1, width=6);
What Are The Differences Between The Two Different String Types?
1) The "String" is an owned buffer of UTF-8 bytes allocated on the heap. 2) The "Strings" are Mutable and it can be modified. 3) The "&str" is a primitive type and it is implemented by the Rust language while String is implemented in the standard library.
How to print with positional arguments?
println!("B:{1}, A:{0}", "Alice", "Bob");
Section 2
(7 cards)