# How to Do RGB to Hex Conversion in Rust

## The challenge

The rgb function is incomplete. Complete it so that passing in RGB decimal values will result in a hexadecimal representation being returned. Valid decimal values for RGB are 0 – 255. Any values that fall out of that range must be rounded to the closest valid value.

Note: Your answer should always be 6 characters long, the shorthand with 3 will not work here.

The following are examples of expected output values:

``````challenge.rgb(255, 255, 255) -- returns FFFFFF
challenge.rgb(255, 255, 300) -- returns FFFFFF
challenge.rgb(0, 0, 0) -- returns 000000
challenge.rgb(148, 0, 211) -- returns 9400D3
``````

## The solution in Rust

Option 1:

``````fn rgb(r: i32, g: i32, b: i32) -> String {
format!(
"{:02X}{:02X}{:02X}",
r.clamp(0, 255),
g.clamp(0, 255),
b.clamp(0, 255)
)
}
``````

Option 2:

``````fn rgb(r: i32, g: i32, b: i32) -> String {
format!("{0:02X}{1:02X}{2:02X}", r.min(255).max(0), g.min(255).max(0), b.min(255).max(0))
}
``````

Option 3:

``````fn rgb(r: i32, g: i32, b: i32) -> String {
let r = r.min(255).max(0);
let g = g.min(255).max(0);
let b = b.min(255).max(0);
format!("{:02X}{:02X}{:02X}", r, g, b)
}
``````

## Test cases to validate our solution

``````extern crate rand;
use self::rand::Rng;

fn solve(r: i32, g: i32, b: i32) -> String {
let clamp = |x: i32| -> i32 { if x < 0 { 0 } else { if x > 255 { 255 } else { x } } };
format!("{:02X}{:02X}{:02X}", clamp(r), clamp(g), clamp(b))
}
macro_rules! compare {
( \$got : expr, \$expected : expr ) => {
if \$got != \$expected { panic!("Got: {}\nExpected: {}\n", \$got, \$expected); }
};
}

#[cfg(test)]
mod tests {
use self::super::*;

#[test]
fn basic_tests() {
compare!(rgb(0, 0, 0), "000000");
compare!(rgb(1, 2, 3), "010203");
compare!(rgb(255, 255, 255), "FFFFFF");
compare!(rgb(254, 253, 252), "FEFDFC");
compare!(rgb(-20, 275, 125), "00FF7D");
}

#[test]
fn random_tests() {
for _ in 0..50 {