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gf-core/examples/logic/Logic.gf
2006-11-27 10:54:26 +00:00

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-- many-sorted predicate calculus
-- AR 1999, revised 2001 and 2006
abstract Logic = {
cat
Prop ; -- proposition
Dom ; -- domain of quantification
Elem Dom ; -- individual element of a domain
Proof Prop ; -- proof of a proposition
Hypo Prop ; -- hypothesis of a proposition
Text ; -- theorem with proof etc.
fun
-- texts
Statement : Prop -> Text ;
ThmWithProof : (A : Prop) -> Proof A -> Text ;
ThmWithTrivialProof : (A : Prop) -> Proof A -> Text ;
-- logically complex propositions
Disj : (A,B : Prop) -> Prop ;
Conj : (A,B : Prop) -> Prop ;
Impl : (A,B : Prop) -> Prop ;
Abs : Prop ;
Neg : Prop -> Prop ;
Univ : (A : Dom) -> (Elem A -> Prop) -> Prop ;
Exist : (A : Dom) -> (Elem A -> Prop) -> Prop ;
-- inference rules
ConjI : (A,B : Prop) -> Proof A -> Proof B -> Proof (Conj A B) ;
ConjEl : (A,B : Prop) -> Proof (Conj A B) -> Proof A ;
ConjEr : (A,B : Prop) -> Proof (Conj A B) -> Proof B ;
DisjIl : (A,B : Prop) -> Proof A -> Proof (Disj A B) ;
DisjIr : (A,B : Prop) -> Proof B -> Proof (Disj A B) ;
DisjE : (A,B,C : Prop) -> Proof (Disj A B) ->
(Hypo A -> Proof C) -> (Hypo B -> Proof C) -> Proof C ;
ImplI : (A,B : Prop) -> (Hypo A -> Proof B) -> Proof (Impl A B) ;
ImplE : (A,B : Prop) -> Proof (Impl A B) -> Proof A -> Proof B ;
NegI : (A : Prop) -> (Hypo A -> Proof Abs) -> Proof (Neg A) ;
NegE : (A : Prop) -> Proof (Neg A) -> Proof A -> Proof Abs ;
AbsE : (C : Prop) -> Proof Abs -> Proof C ;
UnivI : (A : Dom) -> (B : Elem A -> Prop) ->
((x : Elem A) -> Proof (B x)) -> Proof (Univ A B) ;
UnivE : (A : Dom) -> (B : Elem A -> Prop) ->
Proof (Univ A B) -> (a : Elem A) -> Proof (B a) ;
ExistI : (A : Dom) -> (B : Elem A -> Prop) ->
(a : Elem A) -> Proof (B a) -> Proof (Exist A B) ;
ExistE : (A : Dom) -> (B : Elem A -> Prop) -> (C : Prop) ->
Proof (Exist A B) -> ((x : Elem A) -> Proof (B x) -> Proof C) ->
Proof C ;
-- use a hypothesis
Hypoth : (A : Prop) -> Hypo A -> Proof A ;
-- pronoun
Pron : (A : Dom) -> Elem A -> Elem A ;
} ;