契约

Declares a behavioral contract with method signatures.

Aliases: interface

Syntax: 契约 <name> [<type-params>] <block>

Category#

type

Related#

• 类
• 实现

Examples#

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

Declares a behavioral contract with method signatures.

# =============================================================================
# 契约 — Declares a behavioral contract with method signatures
# =============================================================================
#
# What this teaches:
#   • Declares a behavioral contract with method signatures.
#   • Related keywords: 类, 实现
#
# Common mistakes:
#   • Declaring a `类 实现 Implendum` without implementing all required methods — every method signature in the 契约 must have a body in the 类.
#
# See also: 类, 实现
# =============================================================================

# 契约 definition and implementation
#
# 契约 Nomen { 函数 opus() → <type> }
# 类 Nomen 实现 Implendum { ... }
#
# GRAMMAR:
#   implendumDecl :← '契约' ident '{' methodSig* '}'
#   genusDecl     :← '类' ident '实现' ident '{' ... '}'
#
# EXPECTED OUTPUT:
#   circulus radius: 25
#   quadratum latus: 15

interface Figurabile {
    fn depinge() → void
}

class Circulus implements Figurabile {
    var int radius = 10

    fn depinge() → void {
        print "circulus radius: §"(self.radius)
    }
}

class Quadratum implements Figurabile {
    var int latus = 5

    fn depinge() → void {
        print "quadratum latus: §"(self.latus)
    }
}

main {
    const Circulus circulus ← Circulus { radius = 25 }
    const Quadratum quadratum ← Quadratum { latus = 15 }
    circulus.depinge()
    quadratum.depinge()
}

Expected output:

circulus radius: 25
quadratum latus: 15