kênh

A kênh 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: hằng logic clausa ← s.close()

Category#

endpoint

Related#

• gọi
• sermo
• scrinium
• gửi
• nhận
• con_trỏ

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 `kênh`, the handle `call` returns
#   • `frame<T>` is the en spelling of `khung<T>`, one typed frame
#   • `s.send<T>()` / `s.recv<T>()` are the en spellings of the outbound
#     `gửi<T>` and inbound `nhận<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: gọi, kênh, khung, gửi, nhận, con_trỏ
# =============================================================================

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 kênh 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.

# =============================================================================
# kênh — a conversation closes itself when it completes; `close()` is early.
# =============================================================================
#
# What this teaches:
#   • Completion closes — when the handler returns (or fails), the kênh
#     releases its handler task and router slot at once, even while its
#     handle still sits in a bảng; the handle keeps reading as its result
#   • A pool of many — finished conversations cost nothing while the pool
#     waits on the rest, so a bảng 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 `⇥ văn_bản`; it returns `đúng` when
#     this call closed the handle
#   • Last reference — a kênh 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 kênh 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: gọi, kênh, nhận, làm, bắt
# =============================================================================

@ gọi 'numeri:bis'
hàm bis(số n) → số {
    trả n * 2
}

@ gọi 'numeri:numera'
hàm numera(số n) sinh → số {
    lặp khoảng 0‥n hằng i {
        nhường i
    }
}

@ gọi 'numeri:defice'
hàm defice(số n) → số ⇥ văn_bản {
    ném "defecit §"(n)
}

hàm tổng(danh_sách<số> partes) → số {
    biến số totum ← 0
    lặp từ partes hằng pars {
        totum ← totum + pars
    }
    trả totum
}

bắt_đầu {
    # Four conversations finish at once; their handles wait in the pool.
    biến bảng<số, kênh> piscina ← tập_rỗng
    lặp khoảng 0‥4 hằng i {
        piscina[i] ← gọi 'numeri:bis' (i)
    }

    # A longer conversation streams while the finished ones hold nothing.
    hằng kênh longus ← gọi 'numeri:numera' (5)
    lặp khoảng 0‥4 hằng i {
        ghi_chú piscina[i] ↦ số
    }
    ghi_chú tổng(longus ↦ danh_sách<số>)

    # Reading waits for the handler (a failed read defaults to 0); close()
    # then reports the error the conversation ended with.
    hằng kênh thập_phân ← gọi 'numeri:defice' (7)
    ghi_chú thập_phân ↦ số ⊥ 0
    làm {
        hằng logic clausa ← fractus.close()
        ghi_chú clausa
    } bắt err {
        ghi_chú err
    }

    # Closing early drops the unread reply; a live handler is cancelled.
    làm {
        hằng kênh ultimus ← gọi 'numeri:bis' (21)
        hằng logic clausa ← ultimus.close()
        ghi_chú clausa
    } bắt err {
        ghi_chú err
    }
}

Expected output:

0
2
4
6
10
0
defecit 7
verum