Desempenho e Diagnóstico

Duas somas — loop vs. fórmula fechada — com tempo medido automaticamente.

// Feature: `@benchmark` — measures execution time

// Syntax: `@benchmark`. Prints duration after every call.

// When to use: investigate hotspots, compare implementations, quick

// profiling without manual instrumentation.


@benchmark
fn sum_loop(n: int) -> int {
  var total = 0
  for i in 1..=n {
    total += i
  }
  return total
}

@benchmark
fn sum_formula(n: int) -> int {
  return n * (n + 1) / 2
}

// Same answer — different implementations; the benchmark shows which

// is faster on your machine.

let r1 = sum_loop(1000)
print("loop result = {r1}")

let r2 = sum_formula(1000)
print("formula result = {r2}")
// expected (exact numeric values; timings vary by machine):

//   loop result = 500500

//   formula result = 500500

Entrada, saída e combinação com @memoize para ver o que vem do cache.

// Feature: `@log` — automatically instruments entry/exit

// Syntax: `@log` before the `fn`. Prints args on entry and the return on exit.

// When to use: quick debug without scattering `print` in the body, light

// tracing in local environments.


@log
fn process_data(x: int) -> int {
  return x * 2 + 1
}

let out = process_data(21)
print("result = {out}")

// expected (exact log format depends on the runtime):

//   ... process_data(21) ...

//   ... return 43 ...

//   result = 43


@log
fn greet(name: str, age: int) -> str {
  return "{name} ({age})"
}

print(greet("Alice", 30))

// expected: Alice (30)


// `@log` stacks well with other decorators; useful together with @retry

// to see what happened on each attempt.

@log
@memoize
fn slow_square(n: int) -> int {
  return n * n
}

print(slow_square(7))  // first call — computes

print(slow_square(7))  // second — comes from the cache

// expected: 49 (twice)

Retry silencioso em funções estáveis e composição com @log para ver tentativas.

// Feature: `@retry(n)` — re-executes on failure

// Syntax: `@retry(<attempts>)`. If the function panics, it retries up to n times.

// When to use: flaky I/O (transient HTTP, lock contention, races),

// flaky CI tests, manual backoff retry.


// Simple case: function that always succeeds — retry never triggers.

@retry(3)
fn always_ok() -> str {
  return "success"
}

print(always_ok())

// expected: success


// Function that always succeeds (in production this would be flaky external).

@retry(5)
fn fetch_data(id: int) -> str {
  return "row-{id}"
}

print(fetch_data(42))

// expected: row-42


// Retry usually pairs with @log/@benchmark for diagnosis.

@retry(2)
@log
fn ping() -> str {
  return "pong"
}

print(ping())
// expected: pong