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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.
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.
The type of types, defined as specific token by the Zipperposition format; in other languages, will be represented as a constant (the "$tType" constant in tptp for instance). Used to define new types, or quantify type variables in languages that support polymorphism.
The type of integers, defined as a specific token by the Zipperposition format; in other languages, it might be represented as a constant with a specific name (for isntance, tptp's "$int") .
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, "$o" in tptp).
The constants for the true and false propositional constants. Again defined as lexical token in the Zipperposition format, while treated as a constant in other languages ("$true" in tptp).
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".
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).
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.
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.
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\""
Represents juxtaposition of two terms, usually denoted "t : t'" in most languages, and mainly used to annotated terms with their supposed, or defined, type.
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).
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.
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.
Pi is the polymorphic type quantification, for instance the polymorphic identity function has type: "Pi alpha. alpha -> alpha"
Letin is local binding, takes a list of equality of equivalences whose left hand-side is a variable.
Forall is universal quantification
Exists is existential quantification
Lambda is used for function construction
Choice is the choice operator, also called indefinite description, or also epsilon terms, i.e "Choice x. p(x)" is one "x" such that "p(x)" is true.
Description is the definite description, i.e "Description x. p(x)" is the only "x" that satisfies p.
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).
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.