Encode Method

One we have created a DomainProduct object O, we can use it to turn a specification into a set of integers encoding the tuples corresponding to this specification. We want to allow the user to write specifications with the following abstract syntax:

$\phi\quad{:}{:}{=}\quad v^\ell_i\mid \phi\wedge\phi'\mid \phi\vee\phi'$

A tuple satisfies specification $v^\ell_i$ if it contains value $v^\ell_i$ . It satisfies $\phi\wedge\phi'$ if it satisfies both $\phi$ and $\phi'$ . It satisfies $\phi\vee\phi'$ if it satisfies either $\phi$ or $\phi'$ .

Instead of explicit connectives, we will simply allow a specification to consist of arbitrarily nested lists, eventually bottoming out with domain values. The outer level is interpreted disjunctively, and each nesting switches the interpretation of the connective: thus the 2nd level is interpreted conjunctively, the 3rd disjunctively, etc. For example, let us consider agreement information limited to just gender and person. The specification:

[[masc [1 3]] [fem 2]]

denotes the 3 tuples [masc 1], [masc 3], [fem 2]. However:

[[masc 1 3] [fem 2]]

just denotes [fem 2] since a tuple cannot contain both 1 and 2. The spec:

[[masc 1] fem]

denotes the 4 tuples [masc 1], [fem 1], [fem 2] and [fem 3].

<DomainProduct encode method>=: meth encode(Desc $) {self Disj(Desc $)} end meth Disj(Desc $) case Desc of _|_ then {FoldL Desc fun {$ Accu Desc} {FS.union Accu {self Conj(Desc $)}} end self.empty} [] nil then self.empty else @value2set.Desc end end meth Conj(Desc $) case Desc of _|_ then {FoldL Desc fun {$ Accu Desc} {FS.intersect Accu {self Disj(Desc $)}} end self.full} [] nil then self.full else @value2set.Desc end end