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gf-core/grammars/logic/Logic.gf
2005-09-15 15:22:00 +00:00

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-- many-sorted predicate calculus
-- AR 1999, revised 2001
abstract Logic = {
flags startcat=Prop ; -- this is what you want to parse
cat
Prop ; -- proposition
Dom ; -- domain of quantification
Elem Dom ; -- individual element of a domain
Proof Prop ; -- proof 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 ;
-- progressive implication ŕ la type theory
ImplP : (A : Prop) -> (Proof A -> Prop) -> Prop ;
-- inference rules
data
ConjI : (A,B : Prop) -> Proof A -> Proof B -> Proof (Conj A B) ;
fun
ConjEl : (A,B : Prop) -> Proof (Conj A B) -> Proof A ;
ConjEr : (A,B : Prop) -> Proof (Conj A B) -> Proof B ;
data
DisjIl : (A,B : Prop) -> Proof A -> Proof (Disj A B) ;
DisjIr : (A,B : Prop) -> Proof B -> Proof (Disj A B) ;
fun
DisjE : (A,B,C : Prop) -> Proof (Disj A B) ->
(Proof A -> Proof C) -> (Proof B -> Proof C) -> Proof C ;
data
ImplI : (A,B : Prop) -> (Proof A -> Proof B) -> Proof (Impl A B) ;
fun
ImplE : (A,B : Prop) -> Proof (Impl A B) -> Proof A -> Proof B ;
data
NegI : (A : Prop) -> (Proof A -> Proof Abs) -> Proof (Neg A) ;
fun
NegE : (A : Prop) -> Proof (Neg A) -> Proof A -> Proof Abs ;
AbsE : (C : Prop) -> Proof Abs -> Proof C ;
data
UnivI : (A : Dom) -> (B : Elem A -> Prop) ->
((x : Elem A) -> Proof (B x)) -> Proof (Univ A B) ;
fun
UnivE : (A : Dom) -> (B : Elem A -> Prop) ->
Proof (Univ A B) -> (a : Elem A) -> Proof (B a) ;
data
ExistI : (A : Dom) -> (B : Elem A -> Prop) ->
(a : Elem A) -> Proof (B a) -> Proof (Exist A B) ;
fun
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
Hypo : (A : Prop) -> Proof A -> Proof A ;
-- pronoun
Pron : (A : Dom) -> Elem A -> Elem A ;
def
-- proof normalization; does not tc 13/9/2005
ConjEl _ _ (ConjI _ _ a _) = a ;
ConjEr _ _ (ConjI _ _ _ b) = b ;
DisjE _ _ _ (DisjIl _ _ a) d _ = d a ;
DisjE _ _ _ (DisjIr _ _ b) _ e = e b ;
ImplE _ _ (ImplI _ _ b) a = b a ;
NegE _ (NegI _ b) a = b a ;
UnivE _ _ (UnivI _ _ b) a = b a ;
ExistE A B _ (ExistI A B a b) d = d a b ;
--- ExistE _ _ _ (ExistI _ _ a b) d = d a b ;
--- does not tc 13/9/2005: {a{-2-}<>a{-0-}}
--- moreover: no problem with
--- ConjEr _ _ (ConjI _ _ a _) = a ;
--- But this changes when A B are used instead of _ _
-- Hypo and Pron are identities
Hypo _ a = a ;
Pron _ a = a ;
} ;