قناة

A قناة closes itself when its conversation completes; a pool of many keeps only the unfinished ones open, and close() ends one early and reports its error.

Syntax: ثابت منطقي clausa ← s.close()

Category#

endpoint

Related#

• اتصل
• sermo
• scrinium
• إرسال
• استقبال
• cursor

Examples#

radix/corpus/ad/sermo-channel.fab (canonical · type)#

English reader names for the conversation family: channel, frame, send<T>, recv<T>

# =============================================================================
# channel — the conversation family under the English reader surface.
# =============================================================================
#
# What this teaches:
#   • `channel` is the en spelling of `قناة`, the handle `call` returns
#   • `frame<T>` is the en spelling of `إطار<T>`, one typed frame
#   • `s.send<T>()` / `s.recv<T>()` are the en spellings of the outbound
#     `إرسال<T>` and inbound `استقبال<T>` views
#
# Common mistakes:
#   • treating the words as reserved: `channel`, `frame`, `send` and `recv`
#     are type names only, and stay ordinary identifiers elsewhere
#
# See also: اتصل, قناة, إطار, إرسال, استقبال, cursor
# =============================================================================

fn count_items(channel s) → int {
    var int n ← 0
    for from s.recv<string>().cursor() const item {
        print item.data
        n ← n + 1
    }
    return n
}

main {
    const channel s ← call 'runtime:echo' ("salve")
    const send<value> outbound ← s.send<value>()
    outbound.da("ping")
    outbound.fini()
    print count_items(s)

    const channel second ← call 'runtime:echo' ("vale")
    const frame<string> ∪ none first ← second.recv<string>().accipe()
    print first?.data
}

Expected output:

salve
1
vale

radix/corpus/ad/sermo-close.fab (canonical · method)#

A قناة closes itself when its conversation completes; a pool of many keeps only the unfinished ones open, and close() ends one early and reports its error.

# =============================================================================
# قناة — a conversation closes itself when it completes; `close()` is early.
# =============================================================================
#
# What this teaches:
#   • Completion closes — when the handler returns (or fails), the قناة
#     releases its handler task and router slot at once, even while its
#     handle still sits in a جدول; the handle keeps reading as its result
#   • A pool of many — finished conversations cost nothing while the pool
#     waits on the rest, so a جدول of many sermones is cheap
#   • Explicit close — `s.close()` ends a conversation early (a live handler
#     is cancelled, unread frames are dropped) and reports the error the
#     conversation ended with through `⇥ نص`; it returns `صواب` when
#     this call closed the handle
#   • Last reference — a قناة nobody can reach is closed as a safety net,
#     but errors from that automatic close are lost; call `close()` when the
#     error matters
#
# Common mistakes:
#   • expecting close() to wait — a handler still running is cancelled, so
#     read to the end first when its outcome matters
#   • keeping a قناة inside a reference cycle — a cycle never reaches its
#     last reference, so the compiler warns (WARN031) and it never
#     auto-closes; `close()` it explicitly
#
# See also: اتصل, قناة, استقبال, افعل, التقط
# =============================================================================

@ اتصل 'numeri:bis'
دالة bis(عدد n) → عدد {
    أعد n * 2
}

@ اتصل 'numeri:numera'
دالة numera(عدد n) مولد → عدد {
    كرر نطاق 0‥n ثابت i {
        سلم i
    }
}

@ اتصل 'numeri:defice'
دالة defice(عدد n) → عدد ⇥ نص {
    ارم "defecit §"(n)
}

دالة المجموع(قائمة<عدد> partes) → عدد {
    متغير عدد totum ← 0
    كرر من partes ثابت pars {
        totum ← totum + pars
    }
    أعد totum
}

بداية {
    # Four conversations finish at once; their handles wait in the pool.
    متغير جدول<عدد, قناة> piscina ← فارغ
    كرر نطاق 0‥4 ثابت i {
        piscina[i] ← اتصل 'numeri:bis' (i)
    }

    # A longer conversation streams while the finished ones hold nothing.
    ثابت قناة longus ← اتصل 'numeri:numera' (5)
    كرر نطاق 0‥4 ثابت i {
        اعرض piscina[i] ↦ عدد
    }
    اعرض المجموع(longus ↦ قائمة<عدد>)

    # Reading waits for the handler (a failed read defaults to 0); close()
    # then reports the error the conversation ended with.
    ثابت قناة كسر ← اتصل 'numeri:defice' (7)
    اعرض كسر ↦ عدد ⊥ 0
    افعل {
        ثابت منطقي clausa ← fractus.close()
        اعرض clausa
    } التقط err {
        اعرض err
    }

    # Closing early drops the unread reply; a live handler is cancelled.
    افعل {
        ثابت قناة ultimus ← اتصل 'numeri:bis' (21)
        ثابت منطقي clausa ← ultimus.close()
        اعرض clausa
    } التقط err {
        اعرض err
    }
}

Expected output:

0
2
4
6
10
0
defecit 7
verum