Control Flow

if – no parentheses

In Rust, if does not take parentheses around the condition:

let n = 5;
if n < 10 {
    println!("small");
} else if n < 20 {
    println!("medium");
} else {
    println!("large");
}

In C#: Same logic, but C# uses if (n < 10). In Rust the condition must be a bool (no integer or pointer in condition).

if is an expression

if/else produces a value; you can assign from it:

let n = 5;
let size = if n < 10 { "small" } else { "large" };

In C#: Like the ternary operator: var size = n < 10 ? "small" : "large";. In Rust, both branches must have the same type.

loop, break, continue

Infinite loop with explicit exit:

let mut count = 0;
loop {
    count += 1;
    if count >= 5 {
        break;
    }
}
// break can return a value: let x = loop { break 42; };

In C#: Like while (true) with break/continue. Rust’s loop can return a value via break value.

while

let mut n = 3;
while n > 0 {
    println!("{}", n);
    n -= 1;
}

In C#: Same as while (n > 0) { ... }.

for

Rust’s for always iterates over a range or iterator:

for i in 0..5 {
    println!("{}", i);  // 0, 1, 2, 3, 4
}
for i in 0..=5 {
    println!("{}", i);  // 0, 1, 2, 3, 4, 5
}

In C#: for (int i = 0; i < 5; i++) or foreach (var i in Enumerable.Range(0, 5)). Rust has no C-style for (;;); use for over ranges or iterators.

Key takeaway

if has no parentheses and is an expression. Use loop/while/for; for is over ranges or iterators, not a C-style triple for.