4 files changed, 19 insertions, 14 deletions
diff --git a/source/Syntax/Abstract.hs b/source/Syntax/Abstract.hs
index 23da652..31a1029 100644
--- a/source/Syntax/Abstract.hs
+++ b/source/Syntax/Abstract.hs
@@ -92,8 +92,8 @@ makeTuple = foldr1 ExprPair
 
 
 data Chain
-    = ChainBase (NonEmpty Expr) Sign Relation (NonEmpty Expr)
-    | ChainCons (NonEmpty Expr) Sign Relation Chain
+    = ChainBase (NonEmpty Expr) Sign Relation [Expr] (NonEmpty Expr) -- left arguments, possibly empty list of parameters, right arguments
+    | ChainCons (NonEmpty Expr) Sign Relation [Expr] Chain
     deriving (Show, Eq, Ord)
 
 data Relation
@@ -319,7 +319,7 @@ data DefnHead
     | DefnVerb (Maybe (NounPhrase Maybe)) VarSymbol (VerbOf VarSymbol)
     | DefnNoun VarSymbol (NounOf VarSymbol)
     | DefnSymbolicPredicate PrefixPredicate (NonEmpty VarSymbol)
-    | DefnRel VarSymbol RelationSymbol VarSymbol
+    | DefnRel VarSymbol RelationSymbol [VarSymbol] VarSymbol
     -- ^ E.g.: /@$x \subseteq y$ iff [...@/
     deriving (Show, Eq, Ord)
 
@@ -411,7 +411,7 @@ data Abbreviation
     = AbbreviationAdj VarSymbol (AdjOf VarSymbol) Stmt
     | AbbreviationVerb VarSymbol (VerbOf VarSymbol) Stmt
     | AbbreviationNoun VarSymbol (NounOf VarSymbol) Stmt
-    | AbbreviationRel VarSymbol RelationSymbol VarSymbol Stmt
+    | AbbreviationRel VarSymbol RelationSymbol [VarSymbol] VarSymbol Stmt
     | AbbreviationFun (FunOf VarSymbol) Term
     | AbbreviationEq SymbolPattern Expr
     deriving (Show, Eq, Ord)
diff --git a/source/Syntax/Adapt.hs b/source/Syntax/Adapt.hs
index b338d47..1b5a237 100644
--- a/source/Syntax/Adapt.hs
+++ b/source/Syntax/Adapt.hs
@@ -124,7 +124,7 @@ head = ScanNoun <$> noun
     <|> ScanAdj <$> adj
     <|> ScanVerb <$> verb
     <|> ScanFun <$> fun
-    <|> ScanRelationSymbol <$> relationSymbol
+    <|> ScanRelationSymbol . fst <$> relationSymbol
     <|> ScanFunctionSymbol <$> functionSymbol
     <|> ScanPrefixPredicate <$> prefixPredicate
 
@@ -184,14 +184,19 @@ verb = toLexicalPhrase <$> (var *> pat <* iff)
 fun :: RE Token LexicalPhrase
 fun = toLexicalPhrase <$> (the *> pat <* (is <|> comma))
 
-relationSymbol :: RE Token RelationSymbol
-relationSymbol = math relator' <* iff
+relationSymbol :: RE Token (RelationSymbol, Int)
+relationSymbol = definiendum <* iff
     where
-        relator' = do
+        definiendum = math do
             varSymbol
             rel <- symbol
+            k <- params
             varSymbol
-            pure rel
+            pure (rel, k)
+        params :: RE Token Int
+        params = do
+            vars <- many (sym InvisibleBraceL *> var <* sym InvisibleBraceR)
+            pure (length vars)
 
 functionSymbol :: RE Token FunctionSymbol
 functionSymbol = do
diff --git a/source/Syntax/Concrete.hs b/source/Syntax/Concrete.hs
index 383f348..3c6700b 100644
--- a/source/Syntax/Concrete.hs
+++ b/source/Syntax/Concrete.hs
@@ -84,8 +84,8 @@ grammar lexicon@Lexicon{..} = mdo
     relationSign   <- rule $ pure Positive <|> (Negative <$ command "not")
     relationExpr   <- rule $ RelationExpr <$> (command "mathrel" *> group expr)
     relation       <- rule $ (RelationSymbol <$> relator) <|> relationExpr
-    chainBase      <- rule $ ChainBase <$> exprs <*> relationSign <*> relation <*> exprs
-    chainCons      <- rule $ ChainCons <$> exprs <*> relationSign <*> relation <*> chain
+    chainBase      <- rule $ ChainBase <$> exprs <*> relationSign <*> relation <*> many (brace expr) <*> exprs
+    chainCons      <- rule $ ChainCons <$> exprs <*> relationSign <*> relation <*> many (brace expr) <*> chain
     chain          <- rule $ chainCons <|> chainBase
 
     formulaPredicate  <- rule $ asum $ prefixPredicateOf FormulaPredicate expr <$> HM.keys lexiconPrefixPredicates
@@ -250,7 +250,7 @@ grammar lexicon@Lexicon{..} = mdo
     defnAdj <- rule $ DefnAdj <$> optional (_an *> nounPhrase) <*> var <* _is <*> adjVar
     defnVerb <- rule $ DefnVerb <$> optional (_an *> nounPhrase) <*> var <*> verbVar
     defnNoun <- rule $ DefnNoun <$> var <* _is <* _an <*> nounVar
-    defnRel <- rule $ DefnRel <$> (beginMath *> varSymbol) <*> relator <*> varSymbol <* endMath
+    defnRel <- rule $ DefnRel <$> (beginMath *> varSymbol) <*> relator <*> many (group varSymbol) <*> varSymbol <* endMath
     defnSymbolicPredicate <- rule $ math $ asum $ prefixPredicateOf DefnSymbolicPredicate varSymbol <$> HM.keys lexiconPrefixPredicates
     defnHead <- rule $ optional _write *> asum [defnAdj, defnVerb, defnNoun, defnRel, defnSymbolicPredicate]
 
@@ -269,7 +269,7 @@ grammar lexicon@Lexicon{..} = mdo
     abbreviationVerb  <- rule $ AbbreviationVerb <$> var <*> verbVar <* (_iff <|> _if) <*> stmt <* _dot
     abbreviationAdj   <- rule $ AbbreviationAdj <$> var <* _is <*> adjVar <* (_iff <|> _if) <*> stmt <* _dot
     abbreviationNoun  <- rule $ AbbreviationNoun <$>  var <* _is <* _an <*> nounVar <* (_iff <|> _if) <*> stmt <* _dot
-    abbreviationRel   <- rule $ AbbreviationRel <$> (beginMath *> varSymbol) <*> relator <*> varSymbol <* endMath <* (_iff <|> _if) <*> stmt <* _dot
+    abbreviationRel   <- rule $ AbbreviationRel <$> (beginMath *> varSymbol) <*> relator <*> many (brace varSymbol) <*> varSymbol <* endMath <* (_iff <|> _if) <*> stmt <* _dot
     abbreviationFun   <- rule $ AbbreviationFun <$> (_the *> funVar) <* (_is <|> _denotes) <*> term <* _dot
     abbreviationEq    <- rule $ uncurry AbbreviationEq <$> symbolicPatternEqTerm
     abbreviation      <- rule $ (abbreviationVerb <|> abbreviationAdj <|> abbreviationNoun <|> abbreviationRel <|> abbreviationFun <|> abbreviationEq)
diff --git a/source/Syntax/Lexicon.hs b/source/Syntax/Lexicon.hs
index 4fe8730..7f79294 100644
--- a/source/Syntax/Lexicon.hs
+++ b/source/Syntax/Lexicon.hs
@@ -112,7 +112,7 @@ prefixOps =
     , ([Just (Command "pow"), Just InvisibleBraceL, Nothing, Just InvisibleBraceR], (NonAssoc, "pow"))
     , ([Just (Command "neg"), Just InvisibleBraceL, Nothing, Just InvisibleBraceR], (NonAssoc, "neg"))
     , ([Just (Command "inv"), Just InvisibleBraceL, Nothing, Just InvisibleBraceR], (NonAssoc, "inv"))
-    , ([Just (Command "abs"), Just InvisibleBraceL, Nothing, Just InvisibleBraceR], (NonAssoc, "abs"))    
+    , ([Just (Command "abs"), Just InvisibleBraceL, Nothing, Just InvisibleBraceR], (NonAssoc, "abs"))
     , (ConsSymbol, (NonAssoc, "cons"))
     , (PairSymbol, (NonAssoc, "pair"))
     -- NOTE Is now defined and hence no longer necessary , (ApplySymbol, (NonAssoc, "apply"))