Try Operator
The ? operator is syntactic sugar for propagating errors. Appending ? to a Result-returning expression either unwraps the Ok value or immediately returns the Err to the caller — without requiring an explicit match.
Code
// Try operator (?): encadenar operaciones que pueden fallar, short-circuit en Err
enum Result {
Ok(int),
Err(String)
}
fn parse_positive(s: String) -> Result {
let n: int = string_to_int(s)
if n <= 0 {
return Result.Err("no es positivo: " + s)
}
return Result.Ok(n)
}
fn double_it(n: int) -> Result {
if n > 1000 {
return Result.Err("numero demasiado grande")
}
return Result.Ok(n * 2)
}
// ? propaga el Err automáticamente sin match explícito
fn pipeline(s: String) -> Result {
let n: int = parse_positive(s)?
let d: int = double_it(n)?
return Result.Ok(d + 1)
}
fn show(r: Result) {
match r {
Result.Ok(v) => print("ok: " + int_to_string(v)),
Result.Err(e) => print("err: " + e)
}
}
fn main() -> int {
show(pipeline("42")) // ok: 85 (42*2+1)
show(pipeline("-5")) // err: no es positivo
show(pipeline("2000")) // err: numero demasiado grande
return 0
}Output
ok: 85 err: no es positivo: -5 err: numero demasiado grande
Explanation
Without ?, every fallible call would require a match expression to check for errors before proceeding. The ? operator automates this: if the result is Ok(v), it unwraps v and continues; if it is Err(e), it immediately returns Err(e) from the enclosing function. The function signature must also return a Result for this to work.
The pipeline function chains two fallible steps: parsing a positive integer and doubling it within a limit. Both lines use ?, so the first error encountered short-circuits the rest of the function. When "-5" is passed, parse_positive returns Err immediately and double_it is never called.
This pattern keeps the happy-path logic clean and readable — pipeline reads almost like sequential imperative code — while preserving complete, explicit error handling. It is the preferred style for multi-step operations in Nyx over deeply nested match expressions.