comprehension vs. constraint

Comparison

	comprehension	constraint
Expression	{ a: A | #(a.b) > 0 }	( all a: A | #(a.b) > 0 )
Output	Set	Boolean

Combination

Example:

• Formal Software Design with Alloy 6

  fun named_contents : Dir -> Name -> Object {
    { d : Dir, n : Name, o : Object |
      some e : Entry | e in d.entries and e.name = n and e.object = o }
  }
  

  Or put it more clearly,

  fun named_contents : Dir -> Name -> Object {
    { d : Dir, n : Name, o : Object |
      ( some e : Entry | e in d.entries and e.name = n and e.object = o )
    }
  }