🦀 Tip of the day 13: if/else Returns a Value, So Ternary Can Retire
If you are coming from Java, C++, or JavaScript, you have two separate tools: if/else for control flow, and the ternary operator (? :) for inline value selection. Rust merged them. In Rust, if is an expression. It evaluates to a value, just like match, just like the blocks you saw back in tip 4. That makes the ternary operator redundant, so Rust simply doesn’t have one.
The basics look familiar, minus the parentheses. Rust does not require parentheses around the condition, but the braces are mandatory, even for one-liners:
#![allow(unused)]
fn main() {
let temperature = 35;
if temperature > 30 {
println!("it's hot");
} else if temperature > 20 {
println!("nice out");
} else {
println!("bring a jacket");
}
}Coming from C-style languages, you will forget the braces and add unnecessary parentheses for the first week. The compiler will gently nudge you on both.
Because if returns a value, you can bind the result directly to a variable:
#![allow(unused)]
fn main() {
let weather = if temperature > 30 { "hot" } else { "fine" };
}In Java or C++ you would write temperature > 30 ? "hot" : "fine". In Rust, that syntax does not exist. You already have if. Both branches must return the same type, same rule as match arms.
No implicit truthiness. Unlike C++, Python, or JavaScript, Rust requires the condition to be bool. There is no if (0), if (""), or if (null). If you want to check whether a collection is empty, you write if list.is_empty(), not if !list. This removes an entire class of bugs where a value is accidentally falsy.
let else is the inverse of if let (tip 12). Instead of “if it matches, run this block,” it means “this must match, otherwise bail out”:
#![allow(unused)]
fn main() {
let Ok(config) = load_config() else {
return default_config();
};
// config is available here, no nesting
}The else branch must diverge (return, break, continue, or panic). This keeps the happy path unindented.
Skipping else means the block returns (), Rust’s unit type. That is fine for side effects, but you cannot assign it to anything useful.
The takeaway: Rust’s if is an expression that returns a value, requires real bool conditions, and pairs with let else for clean early exits.
🔇 The ternary operator spent 50 years being the clever shortcut. Rust just made every if clever by default and quietly showed it the door.