默认

Starts the default branch of an 选择 or 匹配 statement.

Aliases: default

Syntax: 默认 <block>

Category#

control-flow

Related#

• 选择
• 匹配

Examples#

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

Starts the default branch of an 选择 or 匹配 statement.

# =============================================================================
# 默认 — Starts the default branch of an 选择 or 匹配 statement.
# =============================================================================
#
# What this teaches:
#   • Default arm — `默认 <block>` is the catch-all branch in an `选择`
#     or `匹配` match expression
#   • Fallback handling — when no `情况` pattern matches, execution falls
#     through to the `默认` block
#
# Common mistakes:
#   • using `默认` with `匹配 全部` — `全部` forbids catchall arms and requires listing every variant explicitly (SEM044)
#
# See also: 选择, 匹配
# =============================================================================

# 默认 — default 选择 arm
#
# GRAMMAR:
#   defaultClause :← '默认' block
#
# EXPECTED OUTPUT:
#   Scalar stdout smoke (see body).
#
# BACKEND:
#   Cross-ref: 选择/ceterum.fab.
#

main {
    const _ 标签 ← "z"
    switch 标签 {
        case "a" { print "a" }
        default { print "default" }
    }
}

Expected output:

default