期约

Promise-like result type associated with async finite functions.

Aliases: promise

Syntax: 期约<T> | 期约<T ⇥ E>

Category#

async

Related#

• 异步
• 未来
• 等定
• 等弃

Examples#

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

Promise-like result type associated with async finite functions.

# =============================================================================
# 期约 — Promise-like result type associated with async finite functions.
# =============================================================================
#
# What this teaches:
#   • Async return type — `期约<T>` is the return-type wrapper for `异步`
#     functions and compatibility `@ 未来` functions.
#   • Failable async return type — `期约<T ⇥ E>` preserves both the
#     resolved value and delayed alternate channel.
#
# Common mistakes:
#   • Creating a `期约<T>` but never awaiting it with `等定`,
#     `等变`, `等返`, or `等弃` — the promise goes unobserved.
#
# See also: 异步, 未来, 等定, 等弃
# =============================================================================

# 期约<T> — async result type (paired with 异步)
#
# 函数 … 异步 → <类型>       -- lowers to 期约<<类型>>
# 函数 … 异步 → <类型> ⇥ E   -- lowers to 期约<<类型> ⇥ E>
#
# GRAMMAR:
#   futuraDecl :← funcDecl '异步'
#
# EXPECTED OUTPUT:
#   期约 类型 notus (promissum.expected).

fn compute() async → int {
    return 7
}

main {
    print "promissum typus notus"
}

Expected output:

promissum typus notus