models.book.chapter4.filesystem.als Maven / Gradle / Ivy

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module chapter4/filesystem ----- The model from page 125

abstract sig Object {}

sig Dir extends Object {contents: set Object}

one sig Root extends Dir { }

sig File extends Object {}

fact {
	Object in Root.*contents
	}

assert SomeDir {
	all o: Object - Root | some contents.o
	}
check SomeDir // This assertion is valid

assert RootTop {
	no o: Object | Root in o.contents
	}
check RootTop // This assertion should produce a counterexample

assert FileInDir {
	all f: File | some contents.f
	}
check FileInDir // This assertion is valid