16 lines
460 B
Racket
16 lines
460 B
Racket
#lang typed/racket
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(require phc-adt
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(lib "phc-graph/graph-type.hl.rkt"))
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(adt-init)
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(define-graph-type g1
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[City [name : String]
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[streets : (Listof Street)]
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[citizens : (Listof Person)]]
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[Street [name : String]
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[houses : (Listof House)]]
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[House [owner : Person]]
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[Person [name : String]]
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#:invariant City.citizens._ ∈ City.streets._.houses._.owner
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#:invariant City.citizens._ ∋ City.streets._.houses._.owner) |