The document appears to be a series of tweets by @brian_pearce discussing learning Rust and its differences from other languages like Python and Ruby. Some key points discussed include Rust's use of Result and Option types to handle errors and absent values instead of exceptions, and how Rust uses these types and match expressions to make error handling more explicit compared to try/catch blocks in other languages. Testing in Rust is also discussed with examples shown of setting up tests with a shared temp directory cleaned up after each test.

1. @brian_pearce
LEARNING TO
THE UNFAMILIAR
Love
with @brian_pearce

2. @brian_pearce

3. @brian_pearce

4. @brian_pearce

5. @brian_pearce
LEARNING TO
THE UNFAMILIAR
Love
with @brian_pearce

6. @brian_pearce
Steep learning curve
at the beginning
1 in 4 People
“
”
- State of Rust Survey 2016

7. @brian_pearce

8. @brian_pearce
def read_file()
with open('my_file.txt') as file:
for line in file: process(line)
def process(line)
if is_a_pun(line):
tell_a_friend()
Python

9. @brian_pearce
fn read_file() {
let mut data = String::new();
let mut f = File::open("my_file.txt").unwrap();
f.read_to_string(&mut data).unwrap();
for line in data.lines() {
process(line);
}
}
fn process(line: &str) {
if is_a_pun(line) {
tell_a_friend();
}
}
Rust

10. @brian_pearce
def read_file(argv)
with open('my_file.txt') as file:
for line in file: process(line)
fn read_file() {
let mut data = String::new();
let mut f = File::open("my_file.txt").unwrap();
f.read_to_string(&mut data).unwrap();
for line in data.lines() {
process(line);
}
}
Python
Rust

11. @brian_pearce
def read_file(argv)
with open('my_file.txt') as file:
for line in file: process(line)
fn read_file() {
let mut data = String::new();
let mut f = File::open("my_file.txt").unwrap();
f.read_to_string(&mut data).unwrap();
for line in data.lines() {
process(line);
}
}
Python
Rust

12. @brian_pearce
Introducing:
The Maybe type
*star wipe*

13. @brian_pearce
Maybes in the
form of:
Option & Result

14. @brian_pearce
enum Option<T> {
Some(T),
None
}
Option:

15. @brian_pearce
Ruby
irb> '7'.to_i

16. @brian_pearce
Ruby
irb> '7'.to_i
=> 7

17. @brian_pearce
Ruby
irb> '7'.to_i
=> 7
irb> '❤'.to_i

18. @brian_pearce
Ruby
irb> '7'.to_i
=> 7
irb> '❤'.to_i
=> 0

19. @brian_pearce
Ruby
irb> '7'.to_i
=> 7
irb> '❤'.to_i
=> 0
irb> '4520000011112222'.to_i
=> 4520000011112222

20. @brian_pearce
Ruby
irb> '7'.to_i
=> 7
irb> '❤'.to_i
=> 0
irb> '4520000011112222'.to_i
=> 4520000011112222
irb> '4520not_a_num2'.to_i

21. @brian_pearce
irb> '7'.to_i
=> 7
irb> '❤'.to_i
=> 0
irb> '4520000011112222'.to_i
=> 4520000011112222
irb> '4520not_a_num2'.to_i
=> 4520
Ruby

22. @brian_pearce
Rust
rust> '7’.to_digit(...)

23. @brian_pearce
Rust
rust> '7’.to_digit(...)
=> Some(7)

24. @brian_pearce
Rust
rust> '7’.to_digit(...)
=> Some(7)
rust> '❤'.to_digit(...)

25. @brian_pearce
Rust
rust> '7’.to_digit(...)
=> Some(7)
rust> '❤'.to_digit(...)
=> None

26. @brian_pearce
Rust
rust> '7’.to_digit(...)
=> Some(7)
rust> '❤'.to_digit(...)
=> None
rust> “4520000011112222”.to_digit(...)
=> Some(4520000011112222)

27. @brian_pearce
Rust
rust> '7’.to_digit(...)
=> Some(7)
rust> '❤'.to_digit(...)
=> None
rust> “4520000011112222”.to_digit(...)
=> Some(4520000011112222)
rust> “4520not_a_num2”.to_digit(...)

28. @brian_pearce
rust> '7’.to_digit(...)
=> Some(7)
rust> '❤'.to_digit(...)
=> None
rust> “4520000011112222”.to_digit(...)
=> Some(4520000011112222)
rust> “4520not_a_num2”.to_digit(...)
=> None
Rust

29. @brian_pearce
Rust
rust> '7’.to_digit(...).unwrap()

30. @brian_pearce
Rust
rust> '7’.to_digit(...).unwrap()
=> 7

31. @brian_pearce
Rust
rust> '7’.to_digit(...).unwrap()
=> 7
rust> '❤'.to_digit(...).unwrap()

32. @brian_pearce
rust> '7’.to_digit(...).unwrap()
=> 7
rust> '❤'.to_digit(...).unwrap()
=> thread 'main' panicked at 'called
`Option::unwrap()` on a `None` value'
Rust

33. @brian_pearce
puts "Enter a number"
num = gets.chomp.to_i
if num.is_a?(Numeric)
puts "Great number choice: #{num}"
else
puts "That wasn't a number"
end
Ruby

34. @brian_pearce
Ruby
puts "Enter a number"
num = gets.chomp.to_i
if num.is_a?(Numeric)
puts "Great number choice: #{num}"
else
puts "That wasn't a number"
end

35. @brian_pearce
Rust
fn main() {
println!("Enter a number");
let mut input = String::new();
io::stdin().
read_line(&mut num).unwrap();
let int = num.to_digit(10).unwrap();
println!("Great number choice: {}", int);
}

36. @brian_pearce
fn main() {
println!("Enter a number");
let mut input = String::new();
io::stdin().
read_line(&mut num).unwrap();
let maybe = num.to_digit(10);
if maybe.is_some() {
let i = maybe.unwrap();
println!("Great number choice: {}", i);
} else if maybe.is_none() {
println!("That wasn't a number");
};
}
Rust

37. @brian_pearce
fn main() {
println!("Enter a number");
let mut input = String::new();
io::stdin().
read_line(&mut num).unwrap();
let maybe = num.to_digit(10);
if maybe.is_some() {
let i = maybe.unwrap();
println!("Great number choice: {}", i);
} else if maybe.is_none() {
println!("That wasn't a number");
};
}
Rust

38. @brian_pearce
fn main() {
println!("Enter a number");
let mut input = String::new();
io::stdin().
read_line(&mut num).unwrap();
let maybe = num.to_digit(10);
match maybe {
Some(n) => {
println!("Great number choice: {}", n);
},
None => {
println!("That wasn't a number");
}
};
Rust

39. @brian_pearce
thread '<unnamed>' panicked at 'cannot access a TLS value during
../src/libcore/option.rs:330
fatal runtime error: Could not unwind stack, error = 5
thread'<unnamed>'panickedat'cannotaccessaTLSva
fatalruntimeerror:Couldnotunwindstack,error=5
Error Handling

40. @brian_pearce
try {
} catch {
}
Java

41. @brian_pearce
begin
rescue
end
Ruby

42. @brian_pearce
try:
expect:
Python

43. @brian_pearce
try!(my_func())

44. @brian_pearce
enum Result<T, E> {
Ok(T),
Err(E)
}
Result

45. @brian_pearce
def read_file(argv)
try:
with open('my_file.txt') as file:
for line in file: process(line)
except:
# Failure
Python

46. @brian_pearce
Rust
fn read_file() {
let mut data = String::new();
let mut f = File::open("my_file.txt").unwrap()
f.read_to_string(&mut data).unwrap();
for line in data.lines() {
process(line);
};
}

47. @brian_pearce
Rust
fn read_file() {
let mut data = String::new();
let mut f = File::open("my_file.txt").unwrap()
f.read_to_string(&mut data).unwrap();
for line in data.lines() {
process(line);
};
}

48. @brian_pearce
Rust
fn read_file() {
let mut data = String::new();
let mut f = File::open("my_file.txt").unwrap()
f.read_to_string(&mut data).unwrap();
for line in data.lines() {
process(line);
};
}

49. @brian_pearce
Rust
fn read_file() -> Result<String, String> {
let mut data = String::new();
let mut f = try!(File::open("my_file.txt"));
f.read_to_string(&mut data).unwrap();
for line in data.lines() {
process(line);
};
}

50. @brian_pearce
Rust
fn read_file() -> Result<String, String> {
let mut data = String::new();
let mut f = try!(
File::open("my_file.txt").map_err(|e| e )
);
f.read_to_string(&mut data).unwrap();
for line in data.lines() {
process(line);
};
}

51. @brian_pearce
fn read_file() -> Result<String, String> {
let mut data = String::new();
let mut f = try!(
File::open("my_file.txt").map_err(|e| e )
);
f.read_to_string(&mut data).unwrap();
for line in data.lines() {
process(line);
};
Ok(“Success”)
}
Rust

52. @brian_pearce
fn my_func() { … }
#[test]
fn my_funct_test { … }
Testing

53. @brian_pearce
bash

54. @brian_pearce
def setup
@dir = '/tmp/rb_tests'
Dir.mkdir(@dir) unless File.directory?(@dir)
end
def teardown
FileUtils.rm_r(@dir)
end
def test_file_write_one
file_name = "#{@dir}/test_one"
File.open(file_name, 'w') { |f| f.write "I failed a google code interview" }
assert File.exists?(file_name)
end
def test_file_write_two
file_name = "#{@dir}/test_two"
File.open(file_name, 'w') { |f| f.write "had a mixup with the interviewer" }
assert File.exists?(file_name)
end
def test_file_write_three
file_name = "#{@dir}/test_three"
File.open(file_name, 'w') { |f| f.write "a mis-understanding of sorts" }
end
Ruby

55. @brian_pearce
def setup
@dir = '/tmp/rb_tests'
Dir.mkdir(@dir) unless File.directory?(@dir)
end
def teardown
FileUtils.rm_r(@dir)
end
def test_file_write_one
file_name = "#{@dir}/test_one"
File.open(file_name, 'w') { |f| f.write "I failed a google code interview" }
assert File.exists?(file_name)
end
def test_file_write_two
file_name = "#{@dir}/test_two"
File.open(file_name, 'w') { |f| f.write "had a mixup with the interviewer" }
assert File.exists?(file_name)
end
def test_file_write_three
file_name = "#{@dir}/test_three"
File.open(file_name, 'w') { |f| f.write "a mis-understanding of sorts" }
end
Ruby

56. @brian_pearce
def setup
@dir = '/tmp/rb_tests'
Dir.mkdir(@dir) unless File.directory?(@dir)
end
def teardown
FileUtils.rm_r(@dir)
end
def test_file_write_one
file_name = "#{@dir}/test_one"
File.open(file_name, 'w') { |f| f.write "I failed a google code interview" }
assert File.exists?(file_name)
end
def test_file_write_two
file_name = "#{@dir}/test_two"
File.open(file_name, 'w') { |f| f.write "had a mixup with the interviewer" }
assert File.exists?(file_name)
end
def test_file_write_three
file_name = "#{@dir}/test_three"
File.open(file_name, 'w') { |f| f.write "a mis-understanding of sorts" }
end
Ruby

57. @brian_pearce
def setup
@dir = '/tmp/rb_tests'
Dir.mkdir(@dir) unless File.directory?(@dir)
end
def teardown
FileUtils.rm_r(@dir)
end
def test_file_write_one
file_name = "#{@dir}/test_one"
File.open(file_name, 'w') { |f| f.write "I failed a google code interview" }
assert File.exists?(file_name)
end
def test_file_write_two
file_name = "#{@dir}/test_two"
File.open(file_name, 'w') { |f| f.write "had a mixup with the interviewer" }
assert File.exists?(file_name)
end
def test_file_write_three
file_name = "#{@dir}/test_three"
File.open(file_name, 'w') { |f| f.write "a mis-understanding of sorts" }
end
Ruby

58. @brian_pearce
fn setup(dir: &String) {
let _ = fs::create_dir(dir)
}
fn teardown(dir: &String) {
let _ = fs::remove_dir(dir);
}
#[test]
fn test_file_write_one() {
let dir_name = format!("/tmp/rs_tests");
let dir = PathBuf::from(dir_name);
setup(&dir);
let file_name = format!("{}/{}", dir_name, "test_one");
let file = File::create(&file_name);
assert! file.exists();
teardown(&dir);
}
#[test]
fn test_file_write_two() {
...
}
Rust

59. @brian_pearce
fn setup(dir: &String) {
let _ = fs::create_dir(dir)
}
fn teardown(dir: &String) {
let _ = fs::remove_dir(dir);
}
#[test]
fn test_file_write_one() {
let dir_name = format!("/tmp/rs_tests");
let dir = PathBuf::from(dir_name);
setup(&dir);
let file_name = format!("{}/{}", dir_name, "test_one");
let file = File::create(&file_name);
assert! file.exists();
teardown(&dir);
}
#[test]
fn test_file_write_two() {
...
}
Rust

60. @brian_pearce
fn setup(dir: &String) {
let _ = fs::create_dir(dir)
}
fn teardown(dir: &String) {
let _ = fs::remove_dir(dir);
}
#[test]
fn test_file_write_one() {
let dir_name = format!("/tmp/rs_tests");
let dir = PathBuf::from(dir_name);
setup(&dir);
let file_name = format!("{}/{}", dir_name, "test_one");
let file = File::create(&file_name);
assert! file.exists();
teardown(&dir);
}
#[test]
fn test_file_write_two() {
...
}
Rust

61. @brian_pearce
fn setup(dir: &String) {
let _ = fs::create_dir(dir)
}
fn teardown(dir: &String) {
let _ = fs::remove_dir(dir);
}
#[test]
fn test_file_write_one() {
let dir_name = format!("/tmp/rs_tests");
let dir = PathBuf::from(dir_name);
setup(&dir);
let file_name = format!("{}/{}", dir_name, "test_one");
let file = File::create(&file_name);
assert! file.exists();
teardown(&dir);
}
#[test]
fn test_file_write_two() {
...
}
Rust

62. @brian_pearce
To prevent from
accomplishing a
purpose or fulfilling
a desire.
“
”

63. @brian_pearce
For the world was built to
develop character, and we
must learn that the
setbacks and grieves which
we endure help us in our
marching onward.
“
”
- Henry Ford

64. @brian_pearce
LEARNING TO
THE UNFAMILIAR
Love
with @brian_pearce