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Module type Term_intf.Logic

module type Logic = sig .. end

Signature used by the Logic class, which parses languages such as tptp, smtlib, etc... Mainly used to parse first-order terms, it is also used to parse tptp's THF language, which uses higher order terms, so some first-order constructs such as conjunction, equality, etc... also need to be represented by standalone terms.
type t
The type of terms.
type id
The type of identifiers used for constants.
type location
The type of locations attached to terms.

Predefined terms


val eq_t : t
val neq_t : t
The terms representing equality and disequality, respectively.
val wildcard : t
The wildcard term, usually used in place of type arguments to explicit polymorphic functions to not explicit types that can be inferred by the type-checker.
val tType : t
The type of types, defined as specific token by the Zipperposition format; in other languages, will be represented as a constant (the "$tType" constant in tptp for instance). Used to define new types, or quantify type variables in languages that support polymorphism.
val prop : t
The type of propositions. Also defined as a lexical token by the Zipperposition format. Will be defined as a constant in most other languages (for instance, "$o" in tptp).
val true_ : t
val false_ : t
The constants for the true and false propositional constants. Again defined as lexical token in the Zipperposition format, while treated as a constant in other languages ("$true" in tptp).
val not_t : t
val or_t : t
val and_t : t
val xor_t : t
val nor_t : t
val nand_t : t
val equiv_t : t
val implied_t : t
val implies_t : t
Standard logical connectives viewed as terms. implies_t is usual right implication, i.e apply implies_t [p; q] is "p implies q", while apply implied_t [p; q ] means "p is implied by q" or "q implies p".
val data_t : t
Term without semantic meaning, used for creating "data" terms. Used in tptp's annotations, and with similar meaning as smtlib's s-expressions (as used in the sexpr function defined later).

Terms leaf constructors


val var : ?loc:location -> id -> t
val const : ?loc:location -> id -> t
Variable and constant constructors. While in some languages they can distinguished at the lexical level (in tptp for instance), in most languages, it is an issue dependant on scoping rules, so terms parsed from an smtlib file will have all variables parsed as constants.
val atom : ?loc:location -> int -> t
Atoms are used for dimacs cnf parsing. Positive integers denotes variables, and negative integers denote the negation of the variable corresponding to their absolute value.
val distinct : ?loc:location -> id -> t
Used in tptp to specify constants different from other constants, for instance the 'distinct' "Apple" should be syntactically different from the "Apple" constant. Can be safely aliased to the const function as the distinct function is always given strings already enclosed with quotes, so in the example above, const would be called with "Apple" as string argument, while distinct would be called with the string "\"Apple\""
val int : ?loc:location -> string -> t
val rat : ?loc:location -> string -> t
val real : ?loc:location -> string -> t
val hexa : ?loc:location -> string -> t
val binary : ?loc:location -> string -> t
Constructors for words defined as numeric formats by the languages specifications. These also can be safely aliased to const.

Term constructors


val colon : ?loc:location ->
       t -> t -> t
Represents juxtaposition of two terms, usually denoted "t : t'" in most languages, and mainly used to annotated terms with their supposed, or defined, type.
val eq : ?loc:location ->
       t -> t -> t
val not_ : ?loc:location -> t -> t
val or_ : ?loc:location -> t list -> t
val and_ : ?loc:location -> t list -> t
val imply : ?loc:location ->
       t -> t -> t
val equiv : ?loc:location ->
       t -> t -> t
Proposition construction functions. The conjunction and disjunction are n-ary instead of binary mostly because they are in smtlib (and that is subsumes the binary case).
val apply : ?loc:location ->
       t -> t list -> t
Application constructor, seen as higher order application rather than first-order application for the following reasons: being able to parse tptp's THF, having location attached to function symbols.
val ite : ?loc:location ->
       t ->
       t -> t -> t
Conditional constructor, both for first-order terms and propositions. Used in the following schema: ite condition then_branch else_branch.
val pi : ?loc:location ->
       t list -> t -> t
val letin : ?loc:location ->
       t list -> t -> t
val forall : ?loc:location ->
       t list -> t -> t
val exists : ?loc:location ->
       t list -> t -> t
val lambda : ?loc:location ->
       t list -> t -> t
val choice : ?loc:location ->
       t list -> t -> t
val description : ?loc:location ->
       t list -> t -> t
Binders for variables. Takes a list of terms as first argument for simplicity, the lists will almost always be a list of variables, optionally typed using the colon term constructor.

Type constructors


val arrow : ?loc:location ->
       t -> t -> t
Function type constructor, for curryfied functions. Functions that takes multiple arguments in first-order terms (and so naturally not curryfied) will take a product as only argument (see the following product function).
val product : ?loc:location ->
       t -> t -> t
Product type constructor, used for instance in the types of functions that takes multiple arguments in a non-curry way.
val union : ?loc:location ->
       t -> t -> t
Union type constructor, currently used in tptp's THF format.
val subtype : ?loc:location ->
       t -> t -> t
Subtype relation for types.

Special constructions


val sequent : ?loc:location ->
       t list -> t list -> t
Sequents as terms
val annot : ?loc:location ->
       t -> t list -> t
Attach a list of attributes (also called annotations) to a term. Attributes have no logical meaning (they can be safely ignored), but may serve to give hints or meta-information.
val sexpr : ?loc:location -> t list -> t
S-expressions (for smtlib attributes), should probably be related to the data_t term.