设

Declares an inferred immutable local.

Syntax: 设 <name> [← <expression>]

Category#

binding

Related#

• 常量
• 变量
• ←

Examples#

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

Declares an inferred immutable local.

# =============================================================================
# 设 — Declares an inferred immutable local.
# =============================================================================
#
# What this teaches:
#   • Immutable binding sugar — `设 name` is a compact alternative to
#     `常量 _ name` for inferred-type immutable locals
#   • Supports immediate init (`设 x ← expr`) and deferred init
#     (`设 x` then `x ← expr` later)
#
# Common mistakes:
#   • Confusing `设` (sugar for `常量 _`) with `变量` — `设` creates an immutable binding.
#
# See also: 常量, 变量, ←
# =============================================================================



# 设 — inferred immutable bindings
#
# Immediate init:
#   设 名称 ← expr        -- compact sugar for 常量 _ 名称 ← expr
#
# Deferred init:
#   设 名称               -- compact sugar for 常量 _ 名称 (assign once later)
#   名称 ← expr
#
# Prefer 设 when a block chains several inferred locals; keep 常量 _ when
# teaching the explicit infer marker or mixing typed and inferred bindings.
#
# GRAMMAR:
#   sitDecl := '设' IDENTIFIER ('←' expression)?
#
# EXPECTED OUTPUT:
#   sit.expected

main {
    let salve ← "Salve"
    let 名称 ← "Marcus"
    let nuntius ← "§, §!"(salve, 名称)

    print nuntius

    let label
    label ← "deferred"
    print label

    const _ idem ← nuntius
    print idem
}

Expected output:

Salve, Marcus!
deferred
Salve, Marcus!