add DimEq.wf and export some things to make it work

lib/Quox/Syntax/DimEq.idr

@@ -72,39 +72,39 @@ fromGround : Context' DimConst d -> DimEq d
 fromGround = C . fromGround'
 
 
-export %inline
+public export %inline
 zeroEq : DimEq 0
 zeroEq = C [<]
 
-export %inline
+public export %inline
 new' : {d : Nat} -> DimEq' d
 new' {d = 0}   = [<]
 new' {d = S d} = new' :< Nothing
 
-export %inline
+public export %inline
 new : {d : Nat} -> DimEq d
 new = C new'
 
 
-private %inline
-shiftMay : Maybe (Dim from) -> Shift from to -> Maybe (Dim to)
-shiftMay p by = map (// by) p
-
-export %inline
+public export %inline
 get' : DimEq' d -> Var d -> Maybe (Dim d)
-get' = getWith shiftMay
+get' = getWith $ \p, by => map (// by) p
 
-private %inline
+public export %inline
+getVar : DimEq' d -> Var d -> Dim d
+getVar eqs i = fromMaybe (B i) $ get' eqs i
+
+public export %inline
 getShift' : Shift len out -> DimEq' len -> Var len -> Maybe (Dim out)
-getShift' = getShiftWith shiftMay
+getShift' = getShiftWith $ \p, by => map (// by) p
 
-export %inline
+public export %inline
 get : DimEq' d -> Dim d -> Dim d
 get _   (K e) = K e
-get eqs (B i) = fromMaybe (B i) $ get' eqs i
+get eqs (B i) = getVar eqs i
 
 
-export %inline
+public export %inline
 equal : DimEq d -> (p, q : Dim d) -> Bool
 equal ZeroIsOne p q = True
 equal (C eqs)   p q = get eqs p == get eqs q
@@ -216,6 +216,19 @@ setSelf (B i)    (C eqs) with (compareP i i) | (compare i.nat i.nat)
   _ | IsGT gt | GT = absurd gt
 
 
+public export
+wf' : DimEq' d -> Bool
+wf' [<]                 = True
+wf' (eqs :< Nothing)    = wf' eqs
+wf' (eqs :< Just (K e)) = wf' eqs
+wf' (eqs :< Just (B i)) = isNothing (get' eqs i) && wf' eqs
+
+public export
+wf : DimEq d -> Bool
+wf ZeroIsOne = True
+wf (C eqs)   = wf' eqs
+
+
 -- [todo] "well formed" dimeqs
 -- [todo] operations maintain well-formedness
 -- [todo] if 'Wf eqs' then 'equal eqs' is an equivalence