bắt

Starts a catch block.

Aliases: catch

Syntax: <structured-statement> bắt <name> <block>

Category#

errors

Related#

• làm
• ném
• ⇥

Examples#

radix/corpus/cape/cape.fab (canonical · keyword)#

Starts a catch block.

# =============================================================================
# bắt — Starts a catch block.
# =============================================================================
#
# What this teaches:
#   • Error recovery — `làm { … } bắt err { … }` attempts a block and catches
#     errors with a named handler
#   • Guarded execution — code inside the `làm` block can `ném` errors that
#     are intercepted by the `bắt` handler
#
# Common mistakes:
#   • attaching `bắt` to a bare `{ }` block — `bắt` only attaches to `làm` blocks and structured statements; use `làm { ... } bắt err { ... }`
#
# See also: làm, ném, ⇥
# =============================================================================

# bắt — catch handler on làm
#
# GRAMMAR:
#   facStmt :← 'làm' block 'bắt' ident block
#
# EXPECTED OUTPUT:
#   Scalar stdout smoke (see body).
#
# BACKEND:
#   Rust/Go: làm/cape emit gap (whitelist: bắt/cape.fab).
#

main {
    var int attempt ← 0
    do {
        attempt ← attempt + 1
        if attempt ≻ 1 {
            throw "simulated failure"
        }
        print "attempt §"(attempt)
    }
    catch err {
        print "caught"
    }
}

Expected output:

attempt 1

radix/corpus/cape/receptio-decline.fab (supporting · reject)#

bắt AIR decline rows: whole-loop trong_khi/itera bắt stays out under the loop-spectrum causes, a rethrow from a recovery arm declines (rethrow_in_recovery).

# =============================================================================
# receptio decline — the Tier 0.5 keep-outs stay fail-closed.
# =============================================================================
#
# Decline rows (reject reason in each comment):
#   1. whole-loop bắt on `trong_khi` — one trailing bắt wraps the whole loop
#      (never re-armed per iteration), and the loop spectrum stays an AIR
#      keep-out: SEM059 dum_loop. A loop statement has no normal-exit
#      value, so the recovery arm also fails the outer-type rule:
#      SEM059 recovery_type_mismatch
#   2. whole-loop bắt on `lặp` — same per-loop attachment, same
#      keep-out: SEM059 itera_loop plus recovery_type_mismatch
#   3. rethrow — a throw from inside the catch arm is a rethrow; it
#      declines to Tier 2 fail-closed and is never silently treated as a
#      recovered value: SEM059 rethrow_in_recovery
#
# Common mistakes:
#   • expecting the trailing loop `bắt` to recover per iteration — the
#      handler is per-loop by the grammar; per-iteration recovery would
#      need new syntax and its own goal
#   • expecting a rethrow to admit because the region admitted — the
#      recovery arm is checked as a catch region; throwing from it is the
#      named Tier 2 decline
#
# See also: bắt, trong_khi, lặp, ném, receptio-air
# =============================================================================

# 1. whole-loop bắt on trong_khi — loop-spectrum keep-out
@ radix làn "air"
hàm custos_dum(logic pergo) → trống {
    trong_khi pergo {
        ném "x"
    } bắt err { }
}

# 2. whole-loop bắt on lặp — loop-spectrum keep-out
@ radix làn "air"
hàm custos_itera() → trống {
    lặp khoảng 0‥4 hằng i {
        ném "x"
    } bắt err { }
}

# 3. rethrow — a throw inside the catch arm declines to Tier 2
@ radix làn "air"
hàm reicit(logic malum) → số ⇥ văn_bản {
    làm {
        nếu malum { ném "x" }
        trả 1
    } bắt err {
        ném "reicitur"
    }
    trả 2
}

Expected: compilation rejects this example.