semaphore

Builtin index · Concurrency

result = semaphore(n)

Input: n · Output: result

What it is

Creates a counting semaphore with n (integer, must be non-negative) initial permits.

Overloads

One call shape — this function is not overloaded.

Code	Input	Output	Description
`result = semaphore(n)`	`n` Semaphore, Mutex, or Channelnot documented yet	`result` Semaphore, Mutex, or Channel	Returns a `Semaphore` handle (`type(s) == "semaphore"`); cloning it shares the same counter, the same convention `Mutex`/`Channel` use.

Examples

From the documentation, and run by the build -- the output and the figure below are what the engine actually produced. Simplest first.

s = semaphore(2)                       # 2 permits available

print(semaphore_available(s))          # 2

semaphore_acquire(s)                   # take one

print(semaphore_available(s))          # 1

semaphore_release(s)                   # give it back

print(semaphore_available(s))          # 2

output

2
1
2

from concurrency

How it works

semaphore(n) — a counting semaphore with n initial permits, for bounding concurrent access to a limited shared resource across spawn/parallel for workers (a hardware port, a connection pool, or just an explicit concurrency cap).

From the note above this builtin in the interpreter, where the reasoning was written down as it was built.