diff options
Diffstat (limited to 'misc/Learning rust/index.md')
| -rw-r--r-- | misc/Learning rust/index.md | 320 |
1 files changed, 317 insertions, 3 deletions
diff --git a/misc/Learning rust/index.md b/misc/Learning rust/index.md index dd8b064..9449208 100644 --- a/misc/Learning rust/index.md +++ b/misc/Learning rust/index.md @@ -3,6 +3,8 @@ description: Notes to self about learning rust created: 2026-07-22 --- +[TOC] + The take aways from [__The__ book on rust](https://doc.rust-lang.org/stable/book/) that took my knowledge from point A to B as primarily a Python developer. ## Chapter 2 @@ -123,7 +125,10 @@ fn main() { Finally writing some rust i must admit that i find rusts compiler errors are really friendly, the syntax is plesent and legible, and leads you to handle errors. -### Temperature converter + +### Assignments + +#### Temperature converter ```rust use std::io; @@ -180,7 +185,7 @@ Your code is solid Rust and it mostly avoids common beginner pitfalls from the b It validates me, wow, what a supprise  - +``` 1. split_at(input.len() - 2) is brittle and can be incorrect because you compute the index from the untrimmed string length (so whitespace/newline can break the split). 2. Slicing by byte index is unsafe for general cases; indexing must land on a valid char boundary (your current approach assumes a fixed layout). 3. Parsing by “last 2 characters” assumes the unit is always exactly one character and located at a fixed position; inputs like 22 C, missing unit, etc., will fail or behave unexpectedly. @@ -188,8 +193,317 @@ It validates me, wow, what a supprise ; and take the last non-whitespace character as the unit, then parse the remaining prefix as the number. +``` + +Nothing major, but let's address it to learn. + +<pre> +<span style="font-weight:bold;">diff --git a/src/main.rs b/src/main.rs</span> +<span style="font-weight:bold;">index 9fee6af..2771e71 100644</span> +<span style="font-weight:bold;">--- a/src/main.rs</span> +<span style="font-weight:bold;">+++ b/src/main.rs</span> +<span style="color:teal;">@@ -15,23 +15,17 @@</span> fn main() { + io::stdin() + .read_line(&mut input) + .expect("Failed to read line"); +<span style="color:lime;">+</span><span style="color:lime;"> input = input.trim().to_string();</span> + +<span style="color:red;">- let (temp, unit) = input.trim().split_at(input.len() - 2);</span> +<span style="color:lime;">+</span><span style="color:lime;"> let (temp, unit) = input.split_at(input.len() - 1);</span> + let unit = unit.to_uppercase(); + + let temp: f64 = temp.parse().expect(&format!("Couldn't parse number from: {temp}")); + println!("temp: {temp}, unit: {unit}"); + +<span style="color:red;">- let result_unit: char;</span> +<span style="color:red;">- let result: f64 = match unit.as_str() {</span> +<span style="color:red;">- "F" => {</span> +<span style="color:red;">- result_unit = 'C';</span> +<span style="color:red;">- fahrenheit_to_celsius(temp)</span> +<span style="color:red;">- }</span> +<span style="color:red;">- "C" => {</span> +<span style="color:red;">- result_unit = 'F';</span> +<span style="color:red;">- celsius_to_fahrenheit(temp)</span> +<span style="color:red;">- }</span> +<span style="color:lime;">+</span><span style="color:lime;"> let (result_unit, result) = match unit.as_str() {</span> +<span style="color:lime;">+</span><span style="color:lime;"> "F" => ('C', fahrenheit_to_celsius(temp)),</span> +<span style="color:lime;">+</span><span style="color:lime;"> "C" => ('F', celsius_to_fahrenheit(temp)),</span> + _ => panic!("Unknown unit {unit}"), + }; + println!("{temp}°{unit} = {result}°{result_unit}") +</pre> + + +#### Fibonacci + +```rust +fn main() { + const iterations: usize = 20; + + let mut prev: usize = 0; + let mut cur: usize = 1; + + for _ in 0..iterations - 1 { + let temp: usize = cur; + cur = cur + prev; + println!("{prev} + {temp} = {cur}"); + prev = temp; + } + println!("{iterations}'th fibonacci number is: {cur}"); +} +``` + +```console +❮ cargo run a +warning: constant `iterations` should have an upper case name + --> src/main.rs:2:11 + | +2 | const iterations: usize = 20; + | ^^^^^^^^^^ + | + = note: `#[warn(non_upper_case_globals)]` (part of `#[warn(nonstandard_style)]`) on by default +help: convert the identifier to upper case + | +2 - const iterations: usize = 20; +2 + const ITERATIONS: usize = 20; + | + +warning: `fibonacci` (bin "fibonacci") generated 1 warning (run `cargo fix --bin "fibonacci" -p fibonacci` to apply 1 suggestion) + Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.02s + Running `target/debug/fibonacci a` + +❮ cargo fix --bin "fibonacci" -p fibonacci +error: the working directory of this package has uncommitted changes, and `cargo fix` can potentially perform destructive changes; if you'd like to suppress this error pass `--allow-dirty`, or commit the changes to these files: + + * .gitignore (dirty) + * Cargo.lock (dirty) + * Cargo.toml (dirty) + * src/ (dirty) + + + ~/projects/my_misc/rust/learning/3/fibonacci master ?4 ─────────────────────────── ✘ 101 impure 13:54:46 +❮ cargo fix --bin "fibonacci" -p fibonacci --allow-dirty + Checking fibonacci v0.1.0 (/home/user/projects/my_misc/rust/learning/3/fibonacci) + Fixed src/main.rs (1 fix) + Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.13s +``` + +Again, really nice and native tooling + +```rust +fn main() { + const ITERATIONS: usize = 20; + + let mut prev: usize = 0; + let mut cur: usize = 1; + + for _ in 0..ITERATIONS - 1 { + let temp: usize = cur; + cur = cur + prev; + println!("{prev} + {temp} = {cur}"); + prev = temp; + } + println!("{ITERATIONS}'th fibonacci number is: {cur}"); +} +``` + +```console +$ cargo run +0 + 1 = 1 +1 + 1 = 2 +1 + 2 = 3 +2 + 3 = 5 +3 + 5 = 8 +5 + 8 = 13 +8 + 13 = 21 +13 + 21 = 34 +21 + 34 = 55 +34 + 55 = 89 +55 + 89 = 144 +89 + 144 = 233 +144 + 233 = 377 +233 + 377 = 610 +377 + 610 = 987 +610 + 987 = 1597 +987 + 1597 = 2584 +1597 + 2584 = 4181 +2584 + 4181 = 6765 +20'th fibonacci number is: 6765 +``` + +Correct + +``` +89 1779979416004714189 + 2880067194370816120 = 4660046610375530309 +90 2880067194370816120 + 4660046610375530309 = 7540113804746346429 +91 4660046610375530309 + 7540113804746346429 = 12200160415121876738 + +thread 'main' (266042) panicked at src/main.rs:9:15: +attempt to add with overflow +note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace +``` + +Currious, if i keep running it, i outgrow the instruction set of `usize` on x86_64, +19.740.274.219.868.223.167 > 2^64 (18,446,744,073,709,551,616) + +```python-console +>>> 7540113804746346429 + 12200160415121876738 +19740274219868223167 +``` + +Python don't care, will have to keep that in mind. +Useful for efficiency and embedded systems. + +#### Twelve days of christmas + +```rust +const DAYS: [&str; 12] = ["first", "second", "third", "fourth", "fifth", "sixth", + "seventh","eighth", "ninth", "tenth", "eleventh", "twelfth"]; + +const THINGS: [&str; 12] = [ + "A partridge in a pear tree", + "Two turtle doves and", + "Three french hens", + "Four calling birds", + "Five golden rings", + "Six geese a-laying", + "Seven swans a-swimming", + "Eight maids a-milking", + "Nine ladies dancing", + "Ten lords a-leaping", + "Eleven pipers piping", + "Twelve drummers drumming" +]; + +fn main() { + for i in 0..12 { + println!("On the {} day of Christmas, my true love sent to me", DAYS[i]); + for j in (0..i + 1).rev() { + println!("{}", THINGS[j]); + } + println!(); + } +} +``` + +``` +On the first day of Christmas, my true love sent to me +A partridge in a pear tree + +On the second day of Christmas, my true love sent to me +Two turtle doves and +A partridge in a pear tree + +On the third day of Christmas, my true love sent to me +Three french hens +Two turtle doves and +A partridge in a pear tree + +On the fourth day of Christmas, my true love sent to me +Four calling birds +Three french hens +Two turtle doves and +A partridge in a pear tree + +On the fifth day of Christmas, my true love sent to me +Five golden rings +Four calling birds +Three french hens +Two turtle doves and +A partridge in a pear tree + +On the sixth day of Christmas, my true love sent to me +Six geese a-laying +Five golden rings +Four calling birds +Three french hens +Two turtle doves and +A partridge in a pear tree + +On the seventh day of Christmas, my true love sent to me +Seven swans a-swimming +Six geese a-laying +Five golden rings +Four calling birds +Three french hens +Two turtle doves and +A partridge in a pear tree + +On the eighth day of Christmas, my true love sent to me +Eight maids a-milking +Seven swans a-swimming +Six geese a-laying +Five golden rings +Four calling birds +Three french hens +Two turtle doves and +A partridge in a pear tree + +On the ninth day of Christmas, my true love sent to me +Nine ladies dancing +Eight maids a-milking +Seven swans a-swimming +Six geese a-laying +Five golden rings +Four calling birds +Three french hens +Two turtle doves and +A partridge in a pear tree + +On the tenth day of Christmas, my true love sent to me +Ten lords a-leaping +Nine ladies dancing +Eight maids a-milking +Seven swans a-swimming +Six geese a-laying +Five golden rings +Four calling birds +Three french hens +Two turtle doves and +A partridge in a pear tree + +On the eleventh day of Christmas, my true love sent to me +Eleven pipers piping +Ten lords a-leaping +Nine ladies dancing +Eight maids a-milking +Seven swans a-swimming +Six geese a-laying +Five golden rings +Four calling birds +Three french hens +Two turtle doves and +A partridge in a pear tree + +On the twelfth day of Christmas, my true love sent to me +Twelve drummers drumming +Eleven pipers piping +Ten lords a-leaping +Nine ladies dancing +Eight maids a-milking +Seven swans a-swimming +Six geese a-laying +Five golden rings +Four calling birds +Three french hens +Two turtle doves and +A partridge in a pear tree +``` + +Again super error message for newcomers with helpful suggestion on how to remedy the issue. + +<pre> +<span style="font-weight:bold;"></span><span style="font-weight:bold;filter: contrast(70%) brightness(190%);color:green;"> Compiling</span> twelve_days_of_christmas v0.1.0 (/home/user/projects/my_misc/rust/learning/3/twelve_days_of_christmas) +<span style="font-weight:bold;"></span><span style="font-weight:bold;filter: contrast(70%) brightness(190%);color:red;">error</span><span style="font-weight:bold;">: missing type for `const` item</span> + <span style="font-weight:bold;"></span><span style="font-weight:bold;filter: contrast(70%) brightness(190%);color:blue;">--> </span>src/main.rs:1:12 + <span style="font-weight:bold;"></span><span style="font-weight:bold;filter: contrast(70%) brightness(190%);color:blue;">|</span> +<span style="font-weight:bold;"></span><span style="font-weight:bold;filter: contrast(70%) brightness(190%);color:blue;">1</span> <span style="font-weight:bold;"></span><span style="font-weight:bold;filter: contrast(70%) brightness(190%);color:blue;">|</span> const DAYS: = ["first", "second", "third", "fourth", "fifth", "sixth", + <span style="font-weight:bold;"></span><span style="font-weight:bold;filter: contrast(70%) brightness(190%);color:blue;">|</span> <span style="font-weight:bold;"></span><span style="font-weight:bold;filter: contrast(70%) brightness(190%);color:red;">^</span> <span style="font-weight:bold;"></span><span style="font-weight:bold;filter: contrast(70%) brightness(190%);color:blue;">help: provide a type for the constant: `[&str; 12]`</span> + +<span style="font-weight:bold;"></span><span style="font-weight:bold;filter: contrast(70%) brightness(190%);color:red;">error</span>: could not compile `twelve_days_of_christmas` (bin "twelve_days_of_christmas") due to 1 previous error +</pre> --- -### Chapter 4 +## Chapter 4 |